Biotinidase Deficiency: a Treatable Neurological Inborn Error Of
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,0$-ǯ92/21ǯ0$5&+2019 MEDICINE IN ISRAEL Biotinidase Deficiency: A Treatable Neurological Inborn Error of Metabolism Wisam Hayek MD1*, Yelena Dumin MD PhD2,4*, Galit Tal MD3, Yoav Zehavi MD1, Waheeb Sakran MD1,4 and Ronen Spiegel MD1,4 1Department of Pediatrics B, Emek Medical Center, Afula, Israel 2Clinical Biochemistry Laboratory, Rambam Medical Center, Haifa, Israel 3Metabolic Clinic, Rappaport Children’s Hospital, Rambam Medical Center, Haifa, Israel 4Rappaport School of Medicine, Technion-Israel Institute of Technology, Haifa, Israel of eye pursuit, and lack of social smiling. Laboratory investi- KEY WORDS: biotin, biotinidase deficiency, seizures, inborn error of gations showed normal levels of serum electrolytes, glucose, metabolism, autosomal recessive calcium, magnesium, ammonia, renal function studies, liver IMAJ 2019; 21: 219–221 transaminases, and arterial blood gases. Serum lactate levels were moderately elevated (4.15 mmol/L, normal value < 2.78 mmol/L). Cerebrospinal fluid (CSF) levels were mildly elevated (2.71 mmol/L, normal value < 2.20 mmol/L) Sepsis workup iotinidase deficiency is a rare inborn error of biotin metab- including blood, urine and CSF cultures were normal, as was B olism with autosomal recessive inheritance. Biotinidase is initial CSF analysis. His brain ultrasound was normal. Initial responsible for the recycling of biotin, an essential co-factor electroencephalogram (EEG) showed an abnormal pattern for the normal function of four human enzymatic carboxy- consistent with burst suppression. lases. Complete deficiency of biotinidase is caused by bi-allelic Therapy with phenobarbital was started, but seizure activ- mutations in the BTD gene encoding this key enzyme and ity continued. Metabolic investigations were obtained, and his results mainly in progressive neurological impairment and urinary organic acid analysis using gas chromatography-mass dermatological manifestations. The clinical symptoms of the spectrometry showed significant excretion of 3-hydroxyisova- disease develop gradually in early infancy and are often non- leric acid (3HIA) as well as slightly increased levels of 3-meth- specific, thus presenting a significant diagnostic challenge for ylcrotonoylglycine, methylcitric and 3-hydroxypropionic acids. the pediatrician since a delay in diagnosis will result in irrevers- A minor elevation of methylmalonic acid was also noticed (23 ible neurological deficits [1]. mmol/mol creatinine, normal value < 12 mmol/mol creatinine We describe a 2-month-old male who presented with new- for age) but was absent on repeated urinary organic acid test onset seizures and hypotonia. Metabolic investigations that [Figure 1A]. Blood-spot acylcarnitine profile measured by included analysis of organic acids and acylcarnitine profile UPLC-MS/MS (ultra-performance liquid chromatography– suggested the diagnosis of biotinidase deficiency, enabling early tandem mass spectrometry) showed elevated levels of C5OH initiation of oral biotin that resulted in complete reversal of the carnitine, and of propionylcarnitine (0.78 mmol/L, normal neurologic symptoms. range 0–0.47), and of methylmalonylcarnitine (3.96 mmol/L, normal range 0–1.15). These findings suggested biotinidase deficiency, and the PATIENT DESCRIPTION analysis of biotinidase enzyme activity in serum revealed The male patient is the first offspring of consanguineous par- almost absent enzyme activity (0.1 nmol/min/ml serum, ents of Arab Muslim descent living in a village in the Nazareth normal range 3–8 nmol/min/ml serum). The diagnosis was region. Pregnancy and delivery were uneventful. further confirmed by genetic analysis of theBTD gene, which He presented initially at the age of 2 months with jerky identified a homozygous frameshift mutation c.393delC movements of both upper and lower limbs and up-rolling eyes that is predicted to result in early truncation of the protein consistent with seizures. On examination he had normal vital (p.Phe131Leufs28*). The infant was started on oral biotin 10 signs, but neurological examination displayed marked head lag, mg daily and within a few days showed remarkable improve- truncal hypotonia, combined with generalized hyper-reflexia ment with cessation of seizures, complete resolution of trun- and clonus. In addition, he exhibited abnormal eye contact, lack cal hypotonia and limb hypertonia, and improvement in eye contact and communication. Repeated tests of organic *The first two authors contributed equally to this study acids showed normalization of all biochemical abnormali- 219 MEDICINE IN ISRAEL ,0$-ǯ92/21ǯ0$5&+2019 Figure 1. Urinary organic acids analysis using gas chromatography-mass spectrometry [A] Increased excretion of 3-hydroxyisovaleric A acid (3HIA) (black arrow) and to a lesser degree 3-methylcrotonoylglycine, methylmalonic acid, methylcitric acid, 3-hydroxypropionic acid TIC: 17070307.D\ data.ms 2.4e+07 2.2e+07 2e+07 1.8e+07 1.6e+07 1.4e+07 1.2e+07 Abundance 1e+07 8000000 6000000 4000000 2000000 8.00 10.0010.00 12.0012.00 14.0014.00 16.0016.00 18.0018.00 20.0020.00 22.0022.00 24.0024.00 26.0026.00 28.0028.00 30.0030.00 32.0032.00 Time [B] 3HIA normalized following the initiation of B oral biotin (black arrow). The arrowhead indicates the urinary phenobarbital excretion. This drug was later discontinued TIC: 17070910.D\ data.ms 2.2e+07 2 e +07 1.8e+07 1.6e+07 1.4e+07 1.2e+07 e Abundance 1 +07 8000000 6000000 4000000 2000000 8.008.00 10.0010.00 12.0012.00 14.0014.00 16.0016.00 18.0018.00 20.0020.00 22.0022.00 24.0024.00 26.0026.00 28.0028.00 30.0030.00 32.0032.00 Time GC-MS: Agilent GC 7890A/ MS 5975, Column: Agilent HP-5MS (30 m, 0.25mmX 0.25μm), Internal standards: 2-Phenylbutyric, Tropic, Margaric ties [Figure 1B]. At age 10 months he demonstrates normal or childhood onset of neurological impairment, including growth and development, no dermatologic abnormalities, and new-onset seizures, evolving hypotonia, ataxia, and develop- normal hearing as confirmed by brainstem evoked response mental deterioration, as well as non-neurological symptoms audiometry such as skin rashes, alopecia, hearing loss, and ophthalmo- logic abnormalities. The disease is easily prevented by early administration of pharmacologic doses of oral biotin, which COMMENT compensates for the unavailable recycled biotin. Moreover, Profound biotinidase deficiency is caused by almost com- neurological symptoms that already appeared can be com- plete deficiency (< 10%) of biotinidase enzyme activity and pletely reversed upon early diagnosis and timely biotin is associated with the most severe presentation of infantile administration. 220 ,0$-ǯ92/21ǯ0$5&+2019 MEDICINE IN ISRAEL Since neurological abnormalities are non-specific and can years. Nevertheless, in agreement with the genetic variability develop gradually without being correctly diagnosed, many of biotinidase deficiency in the Israeli (mainly the non-Jewish) countries include this disorder in their newborn screening population and the successful, simple and available treatment, panel [2]. In Israel, biotinidase deficiency is not included in we strongly recommend reconsidering the incorporation of the national newborn screening, posing a major challenge for this disorder into the current Israeli newborn screening, as was pediatricians in timely diagnosing infants with non-specific done for other treatable disorders [5]. neurological symptoms. Rapid initial metabolic investigations In conclusion, biotinidase deficiency is a rare inborn error of are therefore crucial and should be performed in consultation metabolism with neurological sequelae that can be completely with metabolic experts. The laboratory diagnostic clues include prevented by early recognition and appropriate treatment. This elevated serum and/or CSF lactate, elevated propionylcarnitine case report highlights the importance of timely diagnosis and (C3), hydroxyisovalerylcarnitine (C5OH) on blood-spot acyl- treatment of this disorder. A high index of suspicion is crucial carnitine profile, and increased 3HIA excretion in urine. Upon in any child presenting with unexplained neurological dete- initial suspicion, oral biotin should be initiated and biotinidase rioration. activity assessed. The mutation identified in our patient was previously Correspondence described in two patients from the Nazareth region and in Dr. R. Spiegel Dept. of Pediatrics B, Emek Medical Center, Afula 1834111, Israel another patient from Turkey [3]. Notably, in Nazareth and Phone: (972-4) 649-5576 the surrounding villages, we already know of three different Fax: (972-4) 649-5589 deleterious mutations associated with profound biotinidase email: [email protected], [email protected] deficiency including the current c.393delG, in addition to References c.100G>A [4] and c.1613G>A. Of note, the significantly high 1. Wolf B. Biotinidase deficiency. In: Pagon R, Bird T, Dolan C, eds. GeneReviews. carrier state of the c.100G>A mutation in one specific village University of Washington, Seattle, 2000 (updated9 June 2016) https://www.ncbi. with high inbreeding permitted the inclusion of this mutation nlm.nih.gov/books/NBK1322/. 2. Wolf B. Successful outcomes of older adolescents and adults with profound bio- into the Israeli genetic prenatal couple screening program. tinidase deficiency identified by newborn screening. Genet Med 2017; 19: 396-402. According to national health authorities, the successful imple- 3. Wolf B, Jensen K, Hüner G, Demirkol M, et al. Seventeen novel mutations that mentation of the c.100G>A mutation in this program