Arch Dis Child: first published as 10.1136/adc.63.10_Spec_No.1175 on 1 October 1988. Downloaded from

Archives of Disease in Childhood, 1988, 63, 1175-1178

Current topic Prenatal diagnosis of skin diseases

P W SOOTHILL Nuffield Departmenit of Obstetrics and Gynaecology, University of Oxford

The possibility of prenatal diagnosis and abortion of invasive prenatal diagnostic procedures. Although abnormal fetuses reassures many couples consider- successful fetal sampling has been described using ing a pregnancy. Some children are conceived only endoscopic or 'blind' techniques, transabdominal because the pregnancy can be terminated if a ultrasound guided needling has replaced these serious uncorrectable abnormality carried in the methods.>" By holding the ultrasound transducer family is passed on. This paper reviews how skin parallel to the proposed path of the needle, it is pos- diseases can be diagnosed prenatally. Space does sible to identify the target, observe the needle enter not permit reference to most of the original papers the skin, and then guide the needle to the target but there are full recent reviews on this subject. -3 through a safe route." This technique is used to

obtain amniotic fluid (amniocentesis), chorionic villi Protected by copyright. Techniques of prenatal diagnosis (placental biopsy), fetal blood (cordocentesis), and biopsies of fetal tissues. For fetal skin biopsy, cup- (1) STUDIES OF MATERNAL BLOOD ped biopsy forceps (figure) are passed down the Maternal serum a fetoprotein concentration is used needle, opened, pressed on to the fetal skin, closed, to screen for fetal defects which involve a break in and the forceps are then withdrawn through the fetal surface, such as spina bifida or exomphalos. It needle. All of these tests are done as outpatient pro- was hoped that this test would detect fetuses with cedures in an ultrasound clinic under local anaesthe- blistering skin conditions such as epidermolysis tic and without maternal sedation. bullosa. This technique has not proved useful for As these tests are all done in the same way, they these conditions, however, and couples at risk of a are thought to have a similar procedure related risk severe skin disorder should not be over-reassured by of causing fetal death, which in experienced hands is a normal a fetoprotein concentration. about 1%)5 7 X The risk of a pregnancy miscarrying A possibility for the future is to use cell separating after an invasive test, however, is also determined techniques to isolate the small number of fetal cells by the spontaneous abortion rate, which depends on found in maternal blood. This would allow prenatal the gestational age, obstetric history, indication for

diagnosis by the techniques described in section 3 prenatal diagnosis, and many other factors but can http://adc.bmj.com/ without instrumenting the uterus. be much greater than 1%. In those fetuses surviving to delivery at term a fetal skin biopsy site is either (2) ULTRASOUND IMAGING not detectable at birth or perhaps a very small scar is The skin itself is not an organ easily examined by occasionally produced. ultrasound scanning. Syndromes that include skel- Ultrasound guided needling of the pregnant etal or other structural defects, however, can be uterus is associated with almost no serious maternal diagnosed by ultrasound scanning alone. For complications. Fetomaternal haemorrhage does example, severely affected fetuses with Goltz's sometimes occur and so rhesus negative mothers are on September 30, 2021 by guest. syndrome (focal dermal hypoplasia), X linked given an injection of human anti-D immunoglobu- chondrodysplasia punctata, and Ellis-van Creveld lin. Despite this precaution maternal red cell isoim- syndrome (chondroectodermal dysplasia) will mani- munisation to D or other red cell antigens will fest limb abnormalities, which can be diagnosed by occasionally be produced. ultrasound examination at about 18 weeks' gesta- tion. Fetal sexing is often possible by ultrasound and (3) STUDIES OF FETAL CELLS (AMNIOCYTES OR if this shows a fetus is female, invasive diagnostic CHORIONIC VILLI) tests for X linked conditions may be unnecessary. Fetal cells are usually obtained for prenatal diagno- Ultrasound scanning plays an important part in all sis by amniocentesis or placental biopsy (see above). 1175 Arch Dis Child: first published as 10.1136/adc.63.10_Spec_No.1175 on 1 October 1988. Downloaded from

1176 Soothill

I 11 12 13 14 15 -16 17 18 19 |0o Inches Figure Fetal skini biopsy forceps. The cupped tip is drawni ini or out o thie sleev'e bviopetiun¢g or closing the hla1ille.s.

Initially amniocentesis was done after 14 weeks' Bloom's syndrome features an increased sister before 12 weeks but chromatid exchange gestation and placental biopsy rate, Protected by copyright. both these gestational age limits have been chal- has defective DNA repair after ultraviolet irradia- lenged and these tissues can be used over a wide tion, and Cockayne's syndrome cells are extremely range of gestational ages.)5 The great advantage of sensitive to the cytotoxic effect of ultraviolet irradia- fetal cell techniques in prenatal diagnosis, however, tion but show normal DNA repair. is that they can be used earlier in pregnancy than the other approaches currently available. (b) DNA analysis Every nucleated cell contains the entire genome. (a) Cytogenetics Therefore, tests which involve study of the genome Structural abnormalities of chromosomes can be can be done using nucleated cells from any tissue. identified at the metaphase stage of cell division. Some diseases are always produced by a known The number of cells in metaphase can be increased single base mutation so that fetal cells can be by cell culture and by incubation with colchicine. examined for this and no family studies are re- These steps are usually needed with amniocytes, but quired. Usually, however, only the region of a the number of fetal cells obtained and the incidence chromosome that contains the mutation can be of cell division is higher with chorionic villi so that a detected. This is done by studying each family

'direct' cytogenetic preparation can be made and requesting prenatal diagnosis to see whether inheri- http://adc.bmj.com/ gross abnormalities like Down's syndrome can be tance of an identifiable region of DNA is associated excluded within a day. with inheritance of the disease ('gene tracking'). Fetal sexing and abortion of male fetuses can be When this is the case the family is described as used in the case of X linked diseases for which there informative and prenatal diagnosis is possible as is as yet no specific diagnostic test (for example, soon as fetal cells are available (from eight to nine ). Alternatively, if the fetus is weeks' gestation onwards). Conditions with skin shown to be female further investigation such as manifestations in which this can be done include skin biopsy to diagnose X linked hypohidrotic Von Recklinghausen's neurofibromatosis, tuberous on September 30, 2021 by guest. is unnecessary. More de- sclerosis, hypohidrotic ectodermal dysplasia, and tailed cytogenetic analysis including chromosome .() X linked ichythyosis has banding, which usually requires a period of cell been mapped and the mutation (a deletion) detected culture with both amniocytes and chorionic villi, can in many cases but it is unlikely that parents would allow indentification of structural abnormalities of want prenatal diagnosis for this condition. the chromosomes associated with clinical syn- Rapid extension of these techniques to the pre- dromes. Ataxia telangiectasia can be diagnosed by natal diagnosis of a wide range of severe skin increased spontaneous chromosomal breakage es- disorders is expected. Gene mapping requires a pecially at a particular site on chromosome 14. large number of cases, however, especially to Arch Dis Child: first published as 10.1136/adc.63.10_Spec_No.1175 on 1 October 1988. Downloaded from

Prenatal diagnosis of skin diseases 1177 exclude heterogeneity in the mutation locus, and Until earlier diagnosis is possible, however, these many of the skin disorders for which prenatal techniques will continue to prove extremely useful diagnosis could be requested are rare. International and acceptable to many families at risk of severe collaboration is required to facilitate these skin disease. It is essential that before undertaking advances. "' prenatal diagnosis by fetal skin structure there should be good communication between the ob- (c) Biochemical studies stetrician and dermatologist and that during the Unlike the genome, biochemical functions are not biopsy procedure the skin samples should be con- always present in every cell. However, biochemical firmed as adequate by an experienced microscopist. properties of fetal cells can sometimes be used for prenatal diagnosis. When it has been shown that an (a) Epidermal disorders enzyme is normally produced by amniocytes or Keratinisation normally starts at 24-26 weeks. For- chorionic villi at the appropriate gestational age and tunately, some keratinisation diseases can be recog- the absence or reduction of enzyme activity in these nised at 20-22 weeks' gestation because of charac- tissues is associated with the disease, prenatal teristic skin structures (bullous ichthyosiform diagnosis is possible. Enzyme defects that can be erythroderma) or because of an abnormally early diagnosed prenatally in this way include Ehlers- onset of keratinisation (Harlequin , lamel- Danlos syndrome type VI (lysyl hydroxylase) and lar ichthyosis, and Sjogren-Larsson syndrome). type VII (procollagen peptidase), X linked (lysyl oxidase), congenital erythropoietic porphyria (b) syndromes (uroporphyrinogen III cosynthetase), Fabry's dis- The structural components of the dermoepidermal ease (a galactosidase), and a L fructose deficiency. junction start to develop in the first trimester of Other metabolic disorders manifest in fetal cells that pregnancy. Prenatal diagnosis is usually done from can be used for prenatal diagnosis include increased 18-22 weeks but diagnosis of some of these condi- Protected by copyright. uptake of radiolabelled copper in Menkes' syn- tions as early as 15 weeks has been reported. Both drome. junctional and dystrophic types of epidermolysis bullosa, and the Dowling variety of epidermolysis (d) Exfoliative cytology bullosa simplex can be diagnosed by their character- As many amniotic fluid cells are desquamated skin istic planes of separation with ultrastructural abnor- cells, it was hoped that study of these would allow malities and by the use of direct immunofluoresence prenatal diagnosis of skin disorders. This may be using monoclonal antibodies specific for junctional possible in the diagnosis of bullous congenital antigens. ichthyosiform erythroderma but so far this tech- nique has not been used because of problems with (c) Ectodermal dysplasias blood cell contamination, changes with gestational X linked hypohidrotic ectodermal dysplasia can be age and the large number of cell types found in detected by absence of pilosebaceous units in fetal amniotic fluid.2 skin at 20 weeks' gestation, but can now often be diagnosed by use of gene tracking.

(4) STUDIES OF FETAL BLOOD http://adc.bmj.com/ Cordocentesis has a limited role for prenatal diagno- (d) Albinism sis of skin disorders. Syndromes which include skin Tyrosinase negative oculocutaneous albinism can be manifestations that are diagnosable prenatally by diagnosed by ultrastructural examination of hair studies of fetal blood include the Wiskott-Aldrich bulb melanosomes in biopsy specimens of fetal scalp syndrome (abnormal platelets), the Chediak- at 18-20 weeks' gestation. Higashi syndrome (ultrastructural abnormalities of neutrophils), and the Heamansky Pudlak syndrome Conclusion

(ultrastructural abnormalities of platelets and mono- on September 30, 2021 by guest. cytes). The decisions as to whether the risk of having an affected child justifies prenatal diagnosis and (5) FETAL SKIN STRUCTURE. whether the consequences of the disease indicate Prenatal diagnosis of most skin disorders will abortion of an affected fetus must be taken by the eventually be done by the techniques described parents after obtaining as much information as above rather than fetal skin biopsy. This is because possible about the disease and the procedures. fetal skin is not sufficiently mature for such diagno- Some of the conditions now diagnosed only in the sis until an advanced gestational age for subsequent second trimester will in the future be detectable in abortion should the fetus be found to be affected. the first trimester, and the number of diseases for Arch Dis Child: first published as 10.1136/adc.63.10_Spec_No.1175 on 1 October 1988. Downloaded from

1178 Sootdlill which prenatal diagnosis can be offered will in- Sybert VP, liolbrook KA. Prenatal diagnosis aind screening. In: ciease. Doctors advising couples at risk of having a Alper JC. ed. The geio(lerilnatoses. Derinaotlogic clinics. Vol 5, pairt 1. Philatdclphia: WB Saunders. 1987:17-41. child with a severe inherited disease should consider Soothill PW. Nicolaides KH. Rodcck CH. Invisivc tcchniqucs referral for investigations such as family DNA for prcnatal diagnosis and therapy. J Petinaot Med 1987;15: studies, which might allow a diagnosis earlier in the 117-27. pregnancy. Information about these techniques ' Nicolaidcs Kiu, Soothill PW. Roscvcar S. Transaibdominal placental biopsy. L nicet 1987;ii:855-6. might allow them to consider a pregnancy which Nicolaidcs KH. Soothill PW, Rodeck Cli, Campbcll S. they would otherwise niot contemplate. Ultraisound-guidcd umbilical cord and placental blood sampling to aIssess fctdl well-being. Lancet 1986;ii:1t)65-7. 7 of the hazards of I ami vcry gratcftil to Dr D Athcrton lo- advicc dUilngl thc prepara- MRC Working Piirty: An asscssment tiol of, tihiis nianuscript. .imnioccntesis. Bi J Obstet Grtvaecol 1978;85:suLpplcmcnt ll. s Nicolatidcs KH. Soothill l'W. Cordocentcsis. In: Studd J. cd. 1Proes.s in olbstetrcs (a(d gyiaecology. Vol 7. Edinburgh: Chuirchill Livingstonc (in prcss). RC. Gosden References Nicolaides KH. Soothill PW. Rodeck CH. Wiarrcn CM. Why confinc chorioi>lc villis (plaiccntzal) biopsy to the first Holbrook KA, ed. Prenatal diagnosis of genetic skin disease. trimicstcr? l ancet 1986;i:543-4. Seminars in dermatology. Vol 3, part 3. New York: Thieme- Ha;rpcr P. Gcic imiapping and ncurogcnctics. J Med Gentet Stratton Inc, 1984. 1987;24:513-4. 2 Gedde-Dahl T, Wuepper KD, eds. Prenatal diagnosis of herit- able skin diseases. Current problems in dermatology. Vol 16. C'orrcspondencc to Dr PW Soothill. Bristol Miitcrnitv Hospital Basel: Karger, 1987. Bristol BS2 8EG. Protected by copyright. http://adc.bmj.com/ on September 30, 2021 by guest.