7 Disorders of Galactose Metabolism

Gerard T. Berry, Stanton Segal, Richard Gitzelmann

»Whenever you consider a galactose disorder, stop milk feeding first and only then seek a diagnosis!«

7.1 Deficiency of Galactose-1-Phosphate Uridyltransferase – 123 7.1.1 Clinical Presentation – 123 7.1.2 Metabolic Derangement – 123 7.1.3 Genetics – 123 7.1.4 Diagnostic Tests – 124 7.1.5 Treatment and Prognosis – 124

7.2 Uridine Diphosphate-Galactose 4'-Epimerase Deficiency – 126 7.2.1 Clinical Presentation – 126 7.2.2 Metabolic Derangement – 126 7.2.3 Genetics – 126 7.2.4 Diagnostic Tests – 127 7.2.5 Treatment and Prognosis – 127

7.3 Galactokinase Deficiency – 127 7.3.1 Clinical Presentation – 127 7.3.2 Metabolic Derangement – 127 7.3.3 Genetics – 127 7.3.4 Diagnostic Tests – 127 7.3.5 Treatment and Prognosis – 128

7.4 Fanconi-Bickel Syndrome – 128

7.5 Portosystemic Venous Shunting and Hepatic Arterio-Venous Malformations – 128

References – 128 122 Chapter 7 · Disorders of Galactose Metabolism

Galactose Metabolism Together with its 4’-epimer, glucose, galactose forms UDPgalactose (or UDP-N-acetylgalactosomine) by the disaccharide lactose, which is the principal carbo- UDPgalactose 4’-epimerase (GALE). The utilization of II hydrate in milk, providing 40 % of its total energy. UDPgalactose in the synthesis of glycoconjugates in- Ingested, exogenous lactose is hydrolyzed in the small cluding glyco proteins, glycolipids and glycosamino- intestine to galactose (. Fig. 7.1a), and glucose by lac- glycans, and their subsequent degradation (. Fig. 7.1a) tase. Galactose is mainly metabolized into galactose-1- may constitute the pathways of endogenous, de novo phosphate (galac tose-1-P) by galactokinase (GALK). synthesis of galactose. All four of these uridine sugar Galactose-1-P uridyltransferase (GALT) converts uri- nucleotides are used for glycoconjugate synthesis. dine diphosphoglucose (UDPglucose) and galactose- UDPglucose is also the key element in glycogen pro- 1-P into uridine diphosphogalactose (UDPgalactose) duction while UDPgalactose is used for lactose syn- and glucose-1-P. The latter is metabolized into glu- thesis. The UDPglucose pyro phosphorylase enzyme cose-6-P from which glucose, pyruvate and lactate (. Fig. 7.1b) that is primarily responsible for inter- are formed (not illustrated). Galactose can also be conversion of UDPglucose and glucose-1-P can cata- converted into galactitol by aldose reductase, and into lyze, albeit in a limited way, the interconversion of galactonate by galactose dehydro genase. UDPglucose UDPgalactose and galactose-1-P, and also contribute (or UDP-N-acetylglucosamine) can be converted into to endogenous synthesis of galactose.

a

b

. Fig. 7.1a,b. Galactose metabolism (simplified). GALE, UDP diphosphate; UTP, uridine triphosphate. The pathways with multi- galactose 4’-epimerase; GALK, galactokinase; GALT, galactose-1-P ple enzymatic steps are shown by broken lines

uridyltransferase; P, phosphate; PPi, pyrophosphate; UDP, uridine 123 7 7.1 · Deficiency of Galactose-1-Phosphate Uridyltransferase

stopped as soon as galactosemia is considered, and resumed Three inborn errors of galactose metabolism are known. only when a galactose disorder has been excluded. The The most important is classic galactosemia due to presence of a reducing substance in a routine urine speci- galactose-1-phosphate uridyltransferase (GALT) defi- men may be the first diagnostic lead. Galactosuria is present ciency. A complete or near-complete deficiency is life provided the last milk feed does not date back more than a threatening with multiorgan involvement and long- few hours and vomiting has not been excessive. However, term complications [1]. Partial deficiency is usually, owing to the early development of a proximal renal tubular but not always, benign. Uridine diphosphate galactose syndrome, the acutely ill galactosemic infant may also 4-epimerase (GALE) deficiency exists in at least two excrete some glucose, together with an excess of amino forms. The very rare profound deficiency clinically re- acids. While hyperaminoaciduria may aid in the diagnosis, sembles classical galactosemia. The more frequent par- glucosuria often complicates it. When both reducing sugars tial deficiency is usually benign. Galactokinase (GALK) (galactose and glucose) are present and reduction and deficiency is extremely rare and the most insidious, glucose tests are done, and when the former test is strongly since it results in the formation of nuclear cataracts positive and the latter is weakly positive, the discrepancy is without provoking symptoms of intolerance. The Fan- easily overlooked. Glucosuria is recognized, and galactos- coni-Bickel syndrome (Chap. 11) is a congenital disor- uria is missed. On withholding milk, galactosuria ceases, der of galactose transport due to GLUT2 deficiency but amino acids in excess continue to be excreted for a few leading to hypergalactosemia. Other secondary causes days. However, galactitol and galactonate continue to be of impaired liver handling of galactose in the neonatal excreted in large amounts. Albuminuria may also be an period are congenital portosystemic shunting and mul- early finding that disappears with dietary lactose restric- tiple hepatic arteriovenous malformations. tion. Partial transferase deficiency associated with 25% re- sidual GALT activity is usually asymptomatic. It is more frequent than classical galactosemia and is most often dis- 7.1 Deficiency of Galactose-1-Phos- covered in mass newborn screening because of moder- phate Uridyltransferase ately elevated blood galactose (free and/or total) and/or low transferase activity. In partial deficiency with only 7.1.2 Clinical Presentation 10% residual GALT activity, there may be liver disease and mental retardation in patients left untreated during early As over 167 mutations in the GALT gene have been identi- infancy. fied [2–4], different forms of the deficiency exist. Infants with complete or near-complete deficiency of the enzyme (classical galactosemia) have normal weight at birth but, as 7.1.2 Metabolic Derangement they start drinking milk, lose more weight than their healthy peers and fail to regain birth weight. Symptoms appear in Individuals with a profound deficiency of GALT can phos- the second half of the first week and include refusal to feed, phorylate ingested galactose but fail to metabolize galac- vomiting, jaundice and lethargy. Hepatomegaly, edema and tose-1-phosphate. As a consequence, galactose-1-phosphate ascites may follow. Death from sepsis, usually due to E.coli, and galactose accumulate, and the alternate pathway me- may follow within days but it has been noted as early as tabolites, galactitol and galactonate, are formed. Cataract 3 days of age. Symptoms are milder and the course is less formation can be explained by galactitol accumulation. The precipitous when milk is temporarily withdrawn and re- pathogenesis of the hepatic, renal and cerebral disturbances placed by intravenous nutrition. Nuclear cataracts appear is less clear but is probably related to the accumulation of within days or weeks and become irreversible within weeks galactose-1-phosphate and (perhaps) of galactitol. of their appearance. Congenital cataracts and vitreous he- morrhages [5] may also be present. In many countries, newborns with galactosemia are dis- 7.1.3 Genetics covered through mass screening for blood galactose, the transferase enzyme or both; this screening is performed us- The mode of inheritance is autosomal recessive. The birth ing dried blood spots usually collected between the second incidence of classical galactosemia is one in 40,000–60,000. and seventh days. At the time of discovery, the first symp- In Ireland it is one in 10,000–20,000. The gene is situated on toms may already have appeared, and the infant may al- chromosome 9, and over 167 mutations or polymorphisms ready have been admitted to a hospital, usually for jaundice. have been described [2–4; see the following website: http:// Where newborns are not screened for galactosemia or when www.alspac.bris.ac.uk/galtdb/genomic_seq.htm]. Some the results of screening are not yet available, diagnosis rests genotype-phenotype matching is available [6-13]. For in- on clinical awareness. It is crucial that milk feeding be stance, homozygosity for the Q188R mutation, unfortu- 124 Chapter 7 · Disorders of Galactose Metabolism

nately prevalent, has been associated with unfavorable genotype [10]. Assessment involves quantitation of plasma clinical outcome [11–13]. Because transferase polymor- galactose and galactitol, of erythrocyte galactose-1-phos- phism abounds [2–4], partial transferase deficiency is more phate, galactitol, galactonate and GALT activity/enzyme frequent than classical galactosemia. Many allelic variants electrophoresis (isoelectric focusing) and investigation II associated with a partial enzyme defect have been reported, of the parents. Galactose-tolerance tests are notoriously but the best known is the Duarte variant due to a N314D noxious to the child with classical galactosemia and have GALT gene mutation that exists in cis with a small deletion no place in evaluating the need for treatment of partial in the 5´ flanking region [2]. Variants such as the Q188R/ deficiencies. N314D compound heterozygote can be distinguished by enzyme electrophoresis or DNA analysis. The N314D Du- arte variant when combined with the severe Q188R muta- 7.1.5 Treatment and Prognosis tion is almost always benign. Treatment of the newborn with classical galactosemia con- sists of the exclusion of all lactose from the diet. This must 7.1.4 Diagnostic Tests be started immediately after the disorder is suspected clini- cally or following a positive newborn screening results even Diagnosis is made by assaying transferase in heparinized before the results of diagnostic tests are available. When a whole blood or erythrocyte lysates, and/or by measuring lactose-free diet is instituted early enough, symptoms dis- abnormally high levels of galactose-1-phosphate in red appear promptly, jaundice resolves within days, cataracts cells. Where rapid shipment of whole blood is difficult, may clear, liver and kidney functions return to normal and blood dried on filter paper can also be used for a semiquan- liver cirrhosis may be prevented. titative assay. In patients with classical galactosemia, defi- For dietary treatment, the following facts are worthy of ciency of GALT is complete or nearly complete. It should be consideration: noted that, when an infant has received an exchange trans- 4 From early embryonic life on, man is capable of syn- fusion, as is often the case, assays in blood must be post- thesizing UDPgalactose from glucose through the epi- poned for three to four months. In this situation, an assay merase reaction, which converts UDPglucose to UDP- of urinary galactitol will be extremely helpful. Mutation galactose. Therefore, man does not depend on exo- ana lysis of the GALT gene in genomic DNA isolated from genous galactose. Raising a child with galactosemia on leukocytes may indicate a diagnosis of GALT deficiency. In a diet completely devoid of galactose is a lofty goal of some hospitals, a blood specimen, liquid or dried on filter many zealous caregivers; yet, such a diet does not exist! paper, is collected prior to every exchange transfusion. The In fact, and this is a point of contention in long-term finding of reduced transferase activity in parental blood care, an ultra-strict diet has never been shown to be safe may provide additional helpful information since, in hetero- for a patient with GALT deficiency. Utilizing an »evi- zygotes, the enzyme activity in erythrocytes is approximately dence-based medicine« approach, the only therapy that 50% of normal. Cultured skin fibroblasts can also be used is convincingly beneficial is the exclusion of lactose for the enzyme assay. If taken post-mortem, liver or kidney from the diet of a neonate and young infant with galac- cortex may provide diagnostic enzyme information but tosemia. Single reports and anecdotal information sug- these specimens must be adequately collected and frozen, gest that children and/or adults may suffer cataracts since in vivo cell damage and/or autolysis may result in de- [15], liver disease [16] and organic brain disease [17] creased enzyme activity. Antenatal diagnosis is possible by with ingestion of lactose. However, there is no evidence measuring transferase activity in cultured amniotic fluid that galactose contained in fruits and vegetables had cells, biopsied chorionic villi, or amniotic fluid galactitol played a role in these rare patients that may harbor non- [14]. Restricting maternal lactose intake does not interfere GALT modifier genes, which render them more suscep- with a diagnosis based on galactitol measurements in am- tible to complications. niotic fluid. 4 Nonetheless, milligram amounts of galactose cause an In partial transferase deficiency, there is a spectrum of appreciable rise of galactose-1-phosphate in erythro- residual enzyme activities in the erythrocyte with the most cytes (e.g. ~500 mg of galactose in a 70 kg adult with common partial deficiency, the compound heterozygote Q188R/Q188R genotype will increase galactose-1-phos- Duarte/Galactosemia (D/G) defect, having approximately phate by 30% in 8 hours); it is possible that the same 25% of the normal mean activity. As a rule, erythrocyte happens in sensitive tissues, such as brain, liver and galactose-1-phosphate is also elevated. Each newborn with kidney. However, at this time, it is impossible to define partial GALT deficiency must nevertheless be observed toxic tissue levels of galactose-1-phosphate and, there- closely, because allelic variants other than Duarte may be fore, safe amounts of dietary galactose cannot be de- operative, and they may be true clinically relevant variants fined. Patients with relatively increased alternate meta- such as individuals of African descent with a S135L/S135L bolic pathway activities should have greater tolerance 125 7 7.1 · Deficiency of Galactose-1-Phosphate Uridyltransferase

for galactose. More and more cases are being described, 4 Support campaigns for complete food and drug label- albeit most are anecdotal in nature, in which a child or ing adult with classic galactosemia is able to ingest a normal diet without any obvious side-effects [18]. Vegetables and Fruits 4 Patients with galactosemia certainly synthesize galactose Parents must be trained to understand that eliminating all from glucose. This is also true for the fetal-placental galactose from the diet can never be reached. The reason for unit. Healthy pregnant women on a lactose-restricted this is that galactose is present in a great number of vege- diet may give birth to healthy newborns whose tissues tables and fruits [36], as a component of galactolipids and are laden with galactose-containing macromolecules. glycoproteins, in the disaccharide melibiose and in the In newborns first exposed to milk, then diagnosed and oligosaccharides raffinose and stachyose [37, 38]. The latter treated properly, erythrocyte galactose-1-phosphate two contain galactose in alpha-galactosidic linkage not stays high for several weeks. These facts and other hydrolyzable by human small intestinal mucosa in vitro or observations [19–25] are evidence for continuous self- in vivo [38]. They are often considered safe for consump- intoxication [26] by the patient, a matter of concern tion by patients. However, this may not be the case when because of some late complications such as premature the small intestine is colonized by bacteria capable of ovarian failure [27–29] and central nervous system dys- releasing galactose. Theoretically, ingestion of raffinose- function [11, 30–32]. In adults on a strict lactose-exclu- and stachyose-rich vegetables (beans, peas, lentils etc.) by a sion diet, galactose intake was estimated at 20–40 mg/ patient who has diarrhea may lead to enhanced intestinal day; at the same time, they produced more galactose absorption of galactose. However, gastroenterologists have endogenously than they consumed in their diets [21, stated that the small intestine may be colonized even in the 33]. Minimal amounts of galactose from food and hid- absence of diarrhea; obviously, the issue is not closed. In den sources may contribute to erythrocyte galactose-1- addition, the normal inhabitants of the large colon may phosphate, but only real breaks in the diet, such as with facilitate the release of galactose from macromolecules that dairy products, are likely to cause a rise above 6 mg/dl. pass through. Such breaks do not cause any discomfort to the patient who, therefore, never develops aversion to galactose- Cheese containing food. The measurement of urinary galactitol It is not generally known that Swiss cheeses of the Emmen- for monitoring treatment has not been successful when taler, Gruyère, and Tilsiter types are galactose- and lactose- used to identify acute effects, but may be beneficial free, as these sugars are cleared by the fermenting micro- when the ingestion is on a daily basis [33]. organisms [39]. Other hardened cheeses may prove equally safe for patients. Calcium supplements should be prescribed Treatment of the Newborn Infant before cheese is introduced to the child's diet; supplements Treating newborns is comparatively easy, as adequate lac- may also be needed by older children and young adults [40]. tose-free soy-based formulas are available. However, there Calcium prescriptions containing lactobionate [30] may has been concern about the safety of soy-based infant for- also be a source of galactose because the beta-galactosidase mulas containing isoflavones. At present, there is no con- of human intestinal mucosa hydrolyses lactobionate, free- clusive evidence of adverse effects [34]. Elimination of milk ing galactose [41]. and milk products is the mainstay of treatment. Breaks of Discipline Spoon-Feeding Whether single or repeated breaks of discipline (such as When spoon-feeding is started, parents must learn to know occasional ice cream by a school-age child or adult with all other sources of lactose and need assistance from the galactosemia) will cause any damage is unknown. Dietary pediatrician and dietitian, who must have recourse to pub- treatment of female patients is continued during pregnancy lished recommendations [35]. Parents are advised to do the [42]. following: 4 Prepare meals from basic foodstuffs Complications of Treated Galactosemia 4 Avoid canned food, byproducts and preserves unless Mild growth retardation, delayed speech development, ver- they are certified not to contain lactose or dairy prod- bal dyspraxia, difficulties in spatial orientation and visual ucts perception, and mild intellectual deficit have been variably 4 Read and reread labels and declarations of ingredients, described as complications of treated galactosemia. The which may change without notification complete set of sequelae is not necessarily present in every 4 Look out for hidden sources of galactose and lactose patient, and the degree of handicap appears to vary widely. from milk powder, milk solids, hydrolyzed whey (a Ovarian dysfunction, an almost inescapable consequence sweetener labeled as such), drugs in tablet form, tooth- of galactosemia is not prevented even by strict diet and paste, baking additives, fillers, sausages etc. is often signaled early in infancy or childhood by hyper- 126 Chapter 7 · Disorders of Galactose Metabolism

gonadotropism. Less than five women with the Q188R/ fetus [26, 30, 46-48] and in the amniotic fluid [14]. It was Q188R genotype have experienced one or more successful hypothesized [26] that the affected fetus produces galac- pregnancies and deliveries; some of them subsequently tose-1-phosphate endogenously from glucose-1-phosphate developed secondary amenorrhea. Since in female patients, via the pyrophosphorylase/epimerase pathway (. Fig. 7.1), II the number of expected ovulatory cycles is limited, it may which also provides UDPgalactose and, thus, secures the bio- be wise to temporarily suppress cycles by birth-control synthesis of galactolipids and galactoproteins indispensable medication, which is lifted when the young woman wishes for cell differentiation and growth. Since the affected fetus to become pregnant. This is not an established form of does not depend on (but may suffer from) the galactose he therapy, in contrast with chronic estrogen and progesterone receives from his mother via the placenta, galactose restric- supplementation. Prescription is hampered by the fact that tion is the prudent stance for pregnant mothers. Affected seemingly all drug tablets contain lactose, providing 100 mg newborns of treated mothers appear healthy at birth. or more of the noxious sugar per treatment day [33]. How- ever, some female patients have received the birth-control medication containing galactose for many years without 7.2 U ridine Diphosphate-Galactose any obvious side effects [17]. 4’-Epimerase Deficiency

Long-Term Results 7.2.1 Clinical Presentation Several reports have indicated the lack of effectiveness of dietary treatment on long-term complications [1, 11, 28–32, This disorder exists in at least two forms, both of which are 43, 44]. It must be stressed here that said studies were retro- discovered through newborn screening using suitable tests spective, not prospective, and not multicentered using the sensitive to both galactose and galactose-1-phosphate in same instruments and endpoints, and were probably marred dried blood. In the 5 patients from 3 families with the severe by negative selection of patients. There has never been an form of the disorder, the enzyme defect was subtotal [49]. adequate prospective study of patients with galactosemia to The newborns presented with vomiting, jaundice and document the natural history and done in conjunction with hepatomegaly reminiscent of untreated classical galactos- proper dietary monitoring. More recently, the quality of emia; one was found to have elevated blood methionine on life in treated patients has also been called into question newborn screening. All had galactosuria and hyperamino- [45]. Also, some patients, males in particular, manifest an aciduria; one had cataracts, and one had sepsis. In some, introverted personality and/or depression [17]. there was evidence for sensorineural deafness and/or dys- morphic features, but it is unclear whether this is related Treatment of Partial Transferase Deficiency to GALE deficiency per se, as there was a high degree of due to D/G genotype consanguinity in the families of Pakistani/Asian ancestry Because it is impossible to decide whether partial trans- with homozygosity for the V94M GALE gene mutation. ferase deficiency needs to be treated, some centers have Infants with the mild form appear healthy [50]. The adopted a pragmatic approach, prescribing a lactose-free enzyme defect is incomplete; reduced stability and greater formula to all infants discovered by newborn screening for than normal requirement for the coenzyme nicotinamide 1-4 months after birth until erythrocyte galactose-1-phos- adenine dinucleotide have been described [51]. Milk-fed phate levels normalize on a regular diet with lactose. Some newborns with the mild form detected in newborn screen- centers will initiate this transition with a galactose challenge. ing are healthy and have neither hypergalactosemia, galac- For example, if at the end of a 1-week trial with a daily tosuria nor hyperaminoaciduria. supplement of formula containing lactose the erythrocyte galactose-1-phosphate level is below 1 mg/dl the infant will be returned to normal nutrition. Other centers opt for 7.2.2 Metabolic Derangement 1 year of treatment and utilize a 1-month challenge with cow’s milk. The utility of such treatment during early in- The enzyme deficiency provokes an accumulation of UDP- fancy is unknown, and, in fact, some centers will employ no galactose after milk feeding. This build-up also results in treatment at all. the accumulation of galactose-1-phosphate (. Fig. 7.1).

Dietary Treatment in Pregnant Woman at Risk Based on the presumption that toxic metabolites deriving 7.2.3 Genetics from galactose ingested by the heterozygous mother accu- mulate in the galactosemic fetus, mothers are often coun- Epimerase deficiency is inherited as an autosomal-recessive seled to refrain from drinking milk for the duration of preg- trait. The epimerase gene resides on chromosome 1 [52]. nancy. However, despite dietary restriction by the mother, Several mutations have been identified [53–57] and charac- galactose-1-phosphate and galactitol accumulate in the terized including the V94M mutation that was present in a 127 7 7.3 · Galactokinase Deficiency

homozygous form in all of the patients tested with a severe 7.3 Galactokinase Deficiency phenotype [51, 57, 58]. It is also well established that this enzyme catalyzes the conversion of UDP-N-acetylglucos- 7.3.1 Clinical Presentation amine to UDP-N-acetylgalactosamine [57]. A compound heterozygous patient (L183P/N34S) of mixed Pakistani/ Cataracts are the only consistent manifestation of the Caucasian ancestry with a mild form and mental retarda- untreated disorder [58], though pseudotumor cerebri has tion, that may or may not be related to the underlying GALE been described [59]. Liver, kidney and brain damage, as deficiency, has been reported [54]. As in GALT deficiency, seen in transferase deficiency, are not features of untreat- abnormal glycosylation of proteins, that appears to be de- ed galactokinase deficiency, and hypergalactosemia and pendent, at least in part, on lactose consumption, has been galactose/galactitol/glucose diabetes are the only chemical reported in severe GALE deficiency [49] and is thought to signs. be a secondary biochemical complication, not primarily related to the genetic defect. 7.3.2 Metabolic Derangement

7.2.4 Diagnostic Tests Persons with GALK deficiency lack the ability to phos- phorylate galactose (. Fig. 7.1). Consequently, nearly all of The deficiency should be suspected when red cell galac- the ingested galactose is excreted, either as such or as its tose-1-phosphate is measurable while GALT is normal. reduced metabolite, galactitol, formed by aldose reductase. Diagnosis is confirmed by the assay of epimerase in erythro- As in GALT deficiency, cataracts result from the accumula- cytes. Heterozygous parents have reduced epimerase activ- tion of galactitol in the lens [60], causing osmotic swelling ity, a finding that usually helps in the evaluation. Diagnosis of lens fibers and denaturation of proteins. of the severe form is based on the clinical symptoms, chem- ical signs and more marked deficiency of epimerase in red cells. The utility of studying the enzyme deficiency in whole 7.3.3 Genetics white cell pellets, isolated lymphocytes and EBV-trans- formed lymphoblasts in potentially clinically relevant The mode of inheritance is autosomal recessive. In most variant cases is under scrutiny [54]. parts of Europe, in the USA and in Japan, birth incidence is in the order of one in 150,000 to one million. It is higher in the Balkan countries [61], the former Yugoslavia, Rumania 7.2.5 Treatment and Prognosis and Bulgaria, where it favors Gypsies (below). In Gypsies, birth incidence was calculated as one in 2,500. The child with the severe form of epimerase deficiency is Two genes have been reported to encode galactokinase: unable to synthesize galactose from glucose and is, therefore, GK1 on chromosome 17q24 [62] and GK2 on chromosome galactose-dependent. Dietary galactose in excess of actual 15 [63]. Many GK1 mutations have now been described biosynthetic needs will cause accumulation of UDPgalac- [62, 64–71]. The GK1 P28T mutation was identified as the tose and galactose-1-phosphate, the latter being one pre- founder mutation responsible for galactokinase deficiency sumptive toxic metabolite. When the amount of ingested in Gypsies [64, 69] and in immigrants from Bosnia in galactose does not meet biosynthetic needs, synthesis of ga- Berlin [61]. lactosylated compounds, such as galactoproteins and galac- tolipids, is impaired. As there is no easily available chemical parameter on which to base the daily galactose allowance 7.3.4 Diagnostic Tests (such as, e.g., blood phenylalanine in phenylketonuria) treat- ment is extremely difficult. Children known to suffer from Provided they have been fed mother's milk or a lactose- the disorder have impaired psychomotor development. containing formula prior to the test, newborns with the Infants with the mild form of epimerase deficiency defect are discovered by mass screening methods for detect- described thus far have not required treatment, but it is ing elevated blood galactose. If they have been fed glucose- advisable that the family physician or pediatrician examine containing fluid, the screening test could be false-negative. one or two urine specimens for reducing substances and Any chance finding of a reducing substance in urine, espe- exclude aminoaciduria within a couple of weeks after diag- cially in children or adults with nuclear cataracts, calls for nosis, while the infant is still being fed milk. He should also the identification of the excreted substance. In addition to watch the infant's psychomotor progress without, however, galactose, galactitol and glucose may be found. Every per- causing concern to the parents. son with nuclear cataracts ought to be examined for GALK deficiency. Final diagnosis is made by assaying GALK activ- ity in heparinized whole blood, red cell lysates, liver or 128 Chapter 7 · Disorders of Galactose Metabolism

fibroblasts. Heterozygotes have intermediate activity in 3. Tyfield L, Reichardt J, Fridovich-Keil J et al (1999) Classical galactos- erythrocytes. Reports of GALK variants have appeared emia and mutations at the galactose-1-phosphate uridyl trans- [58, 59]. ferase (GALT) gene. Hum Mutat 13:417-430 4. Elsas LJ II, Lai K (1998) The molecular biology of galactosemia. II Genet Med 1:40-48 5. Levy HL, Brown AE, Williams SE et al (1996) Vitreous hemorrhage as 7.3.5 Treatment and Prognosis an ophthalmic complication of galactosemia. J Pediatr 129:922- 925 Treatment may be limited to the elimination of milk from 6. Berry GT, Nissim I, Mazur AT et al (1995) In vivo oxidation of [13C]galactose in patients with galactose-1-phosphate uridyltrans- the diet. Minor sources of galactose, such as milk products, ferase deficiency. Biochem Mol Med 56:158-165 green vegetables, legumes, drugs in tablet form, etc., can 7. Berry GT, Singh RH, Mazur AT et al (2000) Galactose breath testing probably be disregarded, since it can be assumed that the distinguishes variant and severe galactose 1-phosphate uridyl- small amounts of ingested galactose are either metabolized transferase genotypes. Pediatr Res 48:323-328 or excreted before significant amounts of galactitol can be 8. Berry GT, Leslie N, Reynolds R et al (2001) Evidence for alternate galactose oxidation in a patient with deletion of the galactose-1- formed. When diagnosis is made rapidly and treatment be- phosphate uridyltransferase gene. Mol Genet Metab 72:316-321 gun promptly, i.e., during the first two to three weeks of life, 9. Berry GT, Reynolds RA, Yager CT et al (2004)Extended [13C]galactose cataracts can clear. When treatment is late, and cataracts too oxidation studies in patients with galactosemia. Mol Genet Metab dense, they will not clear completely (or at all) and must be 82:130-136 removed surgically. In patients who have had their lenses 10. Henderson H, Leisegang F, Brown R et al (2002) The clinical and molecular spectrum of galactosemia in patients from the Cape removed, recurring cataracts may appear, originating from Town region of South Africa. BMC Pediatr 2:7 remnants of the posterior lens capsule. This can be avoided 11. Shield JPH, Wadsworth EJK, MacDonald A et al (2000) The relation- by continuing the diet. ship of genotype to cognitive outcome in galactosemia. Arch Dis As in carriers with GALT deficiency [72], the specula- Child 83:248-250 tion [73] that heterozygosity for GALK deficiency pre- 12. Guerrero NV, Singh RH, Manatunga A et al (2000) Risk factors for premature ovarian failure in females with galactosemia. J Pediatr disposes to the formation of presenile cataracts remains 137:833-841 unproven [74]. It has been suggested that heterozygotes 13. Webb AL, Singh RH, Kennedy MJ et al (2003) Verbal dyspraxia and res trict their milk intake [73], though scientific proof of galactosemia. Pediatr Res 53:396-402 the merits of this measure is lacking. 14. Jakobs C, Kleijer WJ, Allen J et al (1995) Prenatal diagnosis of galac- tosemia. Eur J Pediatr 154[Suppl 2]:S33-S36 15. Beigi B, O’Keefe M, Bowell R et al (1993) Ophthalmic findings in classical galactosaemia – prospective study. Br J Ophthalmol 7.4 Fanconi-Bickel Syndrome 77:162-164 16. Vogt M, Gitzelmann R, Allemann J (1980) Dekompensierte Leber- This is a recessively inherited disorder of glucose and zirrhose infolge Galaktosämie bei einem 52jährigen Mann. Schweiz galactose transport due to GLUT2 deficiency and is ex- Med Wochenschr 110:1781-1783 17. Berry GT, Segal S (unpublished observations) tremely rare. A few cases have been discovered during new- 18. Lee PJ, Lilburn M, Wendel U et al (2003) A woman with untreated born screening for galactose in blood. For further details, galactosemia. Lancet 362:446 7 Chap. 11. 19. Gitzelmann R (1969) Formation of galactose-1-phosphate from uridine diphosphate galactose in erythrocytes from patients with galactosemia. Pediatr Res 3:279-286 7.5 Portosystemic Venous Shunting 20. Gitzelmann R, Hansen RG (1974) Galactose biogenesis and disposal in galactosemics. Biochim Biophys Acta 372: 374-378 and Hepatic Arterio-Venous 21. Berry GT, Nissin I, Lin Z et al (1995) Endogenous synthesis of galac- Malformations tose in normal men and patients with hereditary galactosaemia. Lancet 346:1073-1074 Portosystemic bypass of splanchnic blood via ductus 22. Berry GT, Nissim I, Gibson JB et al (1997) Quantitative assessment of whole body galactose metabolism in galactosemic patients. Eur venosus Arantii [75] or intrahepatic shunts [76, 77] causes J Pediatr 156[Suppl1]:S43-S49 alimentary hypergalactosemia, which is discovered during 23. Berry GT, Moate PJ, Reynolds RA et al (2004) The rate of de novo metabolic newborn screening. galactose synthesis in patients with galactose-1- phosphate uri- dyltransferase (GALT) deficiency. Mol Genet Metab 81:22-30 24. Schadewaldt P, Kamalanathan L, Hammen H-W et al (2004) Age References dependence of endogenous galactose formation in Q188R homo- zygous galactosemic patients. Mol Genet Metab 81:31-44 25. Forbes GB, Barton LD, Nicholas DL et al (1998) Composition of milk 1. Segal S (1998) Galactosaemia today: The enigma and the challenge. produced by a mother with galactosemia. J Pediatr 113:90-91 J Inherit Metab Dis 21:455-471 26. Gitzelmann R, Hansen RG, Steinmann B (1975) Biogenesis of galac- 2. Tyfield LA (2000) Galactosaemia and allelic variation at the galac- tose, a possible mechanism of self-intoxication in galactosemia. tose-1-phosphate uridyltransferase gene: a complex relationship In: Hommes FA, Van den Berg CJ (eds) Normal and pathological between genotype and phenotype. Eur J Pediatr 159[Suppl 3]: development of energy metabolism. Academic Press, London, S204-S207 p 2537 129 7 References

27. Kaufman FR, Kogut MD, Donnell GN et al (1981) Hypergonado- 51. Gitzelmann R, Steinmann B (1973) Uridine diphosphate galactose tropic hypogonadism in female patients with galactosemia. N Engl 4- epimerase deficiency II. Clinical follow-up, biochemical studies J Med 304:994-998 and family investigation. Helv Paediatr Acta 28:497-510 28. Waggoner DD, Buist NRM, Donnell GN (1990) Long-term prognosis 52. Daude N, Gallaher TK, Zeschnigk M et al (1995) Molecular cloning, in galactosaemia: result of a survey of a 350 cases. J Inherit Metab characterization, and mapping of a full-length cDNA encoding Dis 13:802-818 human UDP-galactose 4‹-epimerase. Biochem Mol Med 56:1-7 29. Gibson JB (1995) Gonadal function in galactosemics and in galac- 53. Maceratesi P, Daude N, Dallapiccola B et al (1998) Human UDP- tose-intoxicated animals. Eur J Pediatr 154[Suppl 2]:S14-S20 galactose 4‹epimerase (GALE) gene and identification of five 30. Komrower GM (1982) Galactosemia – thirty years on. The experi- missense mutations in patients with epimerase-deficiency. Mol ence of a generation. J Inherit Metab Dis 5[Suppl 2]:96-104 Genet Metab 63:26-30 31. Schweitzer S, Shin Y, Jakobs C et al (1993) Long-term outcome in 54. Alano A, Almashanu S, Chinsky JM et al (1998) Molecular character- 134 patients with galactosaemia. Eur J Pediatr 152:36-43 ization of a unique patient with epimerase-deficiency galactosae- 32. Manis FR, Cohn LB, McBride Chang C et al (1997) A longitudinal mia. J Inherit Metab Dis 21:341-350 study of cognitive functioning in patients with classical galactos- 55. Wohlers TM, Christacos NC, Harreman MT et al (1999) Identification aemia, including a cohort treated with oral uridine. J Inherit Metab and characterization of a mutation, in the human UDP-galactose- Dis 20:549-555 4-epimerase gene, associated with generalized epimerase-defi- 33. Berry GT, Palmieri M, Gross KC et al (1993) The effect of dietary ciency galactosemia. Am J Hum Genet 64:462-470 fruits and vegetables on urinary galactitol excretion in galactose- 56. Wohlers TM, Fridovich-Keil JL (2000) Studies of the V94M-sub- 1-phosphate uridyltransferase deficiency. J Inherit Metab Dis stituted human UDPgalactose-4-epimerase enzyme associated 16:91-100 with generalized epimerase-deficiency galactosaemia. J Inherit 34. Merritt RJ, Jenks BH (2004) Safety of soy-based infant formulas Metab Dis 23:713-729 containing isoflavones: the clinical evidence. J Nutr 134:1220S- 57. Schulz JM, Watson AL, Sanders R et al (2004) Determinants of func- 1224S tion and substrate specificity in human UDP-galactose epimerase. 35. Gross KC, Acosta PB (1991) Fruits and vegetables are a source of J Biol Chem 279:32796-32803 galactose: implications in planning the diets of patients with galac- 58. Gitzelmann R (1967) Hereditary galactokinase deficiency a newly tosaemia. J Inherit Metab Dis 14:253-258 recognized cause of juvenile cataracts. Pediatr Res 1:1423 36. Acosta PB, Gross KC (1995) Hidden sources of galactose in the 59. Bosch AM, Bakker HD, VanGennip AH et al (2002) Clinical features environment. Eur J Pediatr 154[Suppl 2]:S8792 of galactokinase deficiency: A review of the literature. J Inherit 37. Wiesmann U, Ros-Beutler B, Schlchter R (1995) Leguminosae in the Metab Dis 25:629-634 diet: The raffinose-stachyose-question. Eur J Pediatr 154[Suppl 2]: 60. Ai Y, Zheng Z, O’Brien-Jenkins A et al (2000) A mouse model of S9396 galactose-induced cataracts. Hum Mol Genet 9:1821-1827 38. Gitzelmann R, Auricchio S (1965) The handling of soya alpha-galac- 61. Reich S, Hennermann J, Vetter B et al (2002) An unexpectedly high tosides by a normal and a galactosemic child. Pediatrics 36:231- frequency of hypergalactosemia in an immigrant Bosnian popula- 235 tion revealed by newborn screening. Pediatr Res 51:598-601 39. Steffen C (1975) Enzymatische Bestimmungsmethoden zur Erfas- 62. Stambolian D, Ai Y, Sidjanin D et al (1995) Cloning the galactokinase sung der Grünungsvorgänge in der milchwirtschaftlichen Techno- cDNA and identification of mutations in two families with cataracts. logie. Lebensm Wiss Technol 8:16 Nat Genet 10:307-312 40. Kaufman FR, Loro ML, Azen C et al (1993) Effect of hypogonadism 63. Lee RT, Peterson GL, Calman AF et al (1992) Cloning of a human and deficient calcium intake on bone density in patients with galactokinase gene (GK2) on chromosome 15 by complementation galactosemia. J Pediatr 123:365-370 in yeast. Proc Natl Acad Sci USA 89:10887-10891 41. Harju M (1990) Lactobionic acid as a substrate of α-galactosidases. 64. Kalaydjieva L, Perez-Lezaun A, Angelicheva D et al (1999) A founder Milchwissenschaft 45:411-415 mutation in the GK1 gene is responsible for galactokinase defi- 42. Sardharwalla IB, Komrower GM, Schwarz V (1980) Pregnancy in ciency in Roma (Gypsies). Am J Hum Genet 65:1299-1307 classical galactosemia. In: Burman D, Holton JB, Pennock CA (eds) 65. Asada M, Okano Y, Imamura T et al (1999) Molecular characteriza- Inherited disorders of carbohydrate metabolism. MTP, Lancaster, tion of galactokinase deficiency in Japanese patients. J Hum Genet pp 125-132 44:377-382 43. Gitzelmann R, Steinmann B (1984) Galactosemia: How does long- 66. Kolosha V, Anoia E, deCespedes C et al (2000) Novel mutations in 13 term treatment change the outcome? Enzyme 32:37-46 probands with galactokinase deficiency. Hum Mutat 15:447-453 44. Holton JB (1996) Galactosaemia: pathogenesis and treatment. 67. Hunter M, Angelicheva D, Levy HL et al (2001) Novel mutations in J Inherit Metab Dis 19:3-7 the GALK1 gene in patients with galactokinase deficiency. Hum 45. Bosch AM, Grootenhuis MA, Bakker HD et al (2004) Living with clas- Mutat 17:77-78 sical galactosemia: health-related quality of life consequences. 68. Okano Y, Asada M, Fujimoto A et al (2001) A genetic factor for Pediatrics 113(5) 423-428 age-related cataract: Identification and characterization of a novel 46. Irons M, Levy HL, Pueschel S et al (1985) Accumulation of galactose- galactokinase variant, “Osaka,” in Asians. Am J Hum Genet 68:1036- 1-phosphate in the galactosaemic fetus despite maternal milk 1042 avoidance. J Pediatr 107:261-263 69. Hunter M, Heyer E, Austerlitz F et al (2002) The P28T mutation in the 47. Holton JB (1995) Effects of galactosemia in utero. Eur J Pediatr 154: GALK1 gene accounts for galactokinase deficiency in Roma (Gypsy) S77- S81 patients across Europe. Pediatr Res 51:602-606 48. Gitzelmann R (1995) Galactose-1-phosphate in the pathophysiol- 70. Timson DJ, Reece RJ (2003) Functional analysis of disease-causing ogy of galactosemia. Eur J Pediatr 154[Suppl 2]:S45-S49 mutations in human galactokinase. Eur J Biochem 270:1767-1774 49. Walter JH, Roberts RE, Besley GT et al (1999) Generalised uridine 71. Sangiuolo F, Magnani M, Stambolian D et al (2004) Biochemical diphosphate galactose-4-epimerase deficiency. Arch Dis Child characterization of two GALK1 mutations in patients with galac- 80:374-376 tokinase deficiency. Hum Mutat 23:396 50. Gitzelmann R, Steinmann B, Mitchell B et al (1976) Uridine diphos- 72. Karas N, Gobec L, Pfeifer V et al (2003) Mutations in galactose-1- phate galactose 4-epimerase deficiency. IV. Report of eight cases in phosphate uridyltransferase gene in patients with idiopathic three families. Helv Paediatr Acta 31:441-445 presenile cataract. J Inherit Metab Dis 26:699-704 130 Chapter 7 · Disorders of Galactose Metabolism

73. Stambolian D, Scarpino-Myers V, Eagle RC Jr et al (1986) Cataracts in patients heterozygous for galactokinase deficiency. Invest Ophthalmol Vis Sci 27:429-433 74. Maraini G, Fielding Hejtmancik J, Shiels A et al (2003) Galactokinase II gene metations and age-related cataract. Lack of association in an Italian population. Mol Vis 9:397-400 75. Gitzelmann R, Arbenz UV, Willi UV (1992) Hypergalactosaemia and portosystemic encephalopathy due to persistence of ductus venosus Arantii. Eur J Pediatr 151:564-568 76. Matsumoto T, Okano R, Sakura N et al (1993) Hypergalactosaemia in a patient with portal-hepatic venous and hepatic arterio-venous shunts detected by neonatal screening. Eur J Pediatr 152:990-992 77. Gitzelmann R, Forster I, Willi UV (1997) Hypergalactosaemia in a newborn: Self-limiting intrahepatic portosystemic venous shunt. Eur J Pediatr 156:719-722