The Androgen Insensitivity Syndrome J Med Genet: First Published As 10.1136/Jmg.33.7.574 on 1 July 1996

5747 JMed Genet 1996;33:574-577 Down syndrome in association with features of the androgen insensitivity syndrome J Med Genet: first published as 10.1136/jmg.33.7.574 on 1 July 1996. Downloaded from

R M Viner, N Shimura, B D Brown, A J Green, I A Hughes

Abstract Increased incidence of anatomical anomalies Three cases of Down syndrome (DS) are such as micropenis,3 hypospadias,4 crypt- reported in association with features ofthe orchidism,35 small testes, and delayed or poor androgen insensitivity syndrome (AIS). pubertal development have been reported in All were 47,XY, + 21 and reared as females. institutionalised cases of DS.3 Two larger stud- One case had a normal female phenotype, ies of male DS cases managed outside in- and two cases showed minimal clitoro- stitutions differed on the nature of sexual megaly and labial fusion. Minor genital development in DS. Peuschel et al6 reported underdevelopment has been reported as normal pubertal gonadal development and sec- common in males with DS; however, AIS ondary sex characteristics, whereas Hsiang et has not previously been associated with al,7 while reporting no increased incidence of DS. Androgen binding studies in genital genital anomalies with respect to the normal skin fibroblasts were normal in two cases population, nevertheless found penile size and and in the 46,XY brother of the third testicular volume to be reduced in comparison who has perineal hypospadias. Mutation to population norms. screening of the androgen receptor (AR) Male pseudohermaphroditism (incomplete gene by PCR-SSCP was normal in all external genital development) in association cases. Normal androgen binding and the with DS has been reported in only two previous absence of an identified mutation in the cases. The first case was a child with a mosaic coding region of the AR gene is very un- karyotype 47,XY,+21/46,XO,+21 in whom usual in AIS, particularly in the complete testes, bifid scotum, perineal hypospadias, and form. This finding suggests the operation female internal genitalia were shown.8 Mo- of hitherto unrecognised genes on chro- saicism for an XO cell line would explain the mosome 21 with a role in androgen re- ambiguous phenotype in this case. The second sponse and sex differentiation. case was 47,XY, + 21 with normal testes, fused (J Med Genet 1996;33:574-577) labioscrotal folds, enlarged phallus, perineal urethral opening, vaginal orifice, and absent Key words: Down syndrome; androgen insensitivity; internal female genitalia by vaginoscopy. Serum http://jmg.bmj.com/ sex determination. testosterone values were not determined, but 24 hour urinary secretion of androgen meta- bolites was normal.9 The case is suggestive of The association of Down syndrome (DS) with AIS, but the diagnosis cannnot be substantiated the androgen insensitivity syndrome (AIS) has without information on testosterone pro- not been DS is a common duction and metabolism. previously reported. on September 27, 2021 by guest. Protected copyright. genetic disorder arising from trisomy 21 usually No studies of androgen metabolism or an- secondary to maternal non-disjunction during drogen receptor binding have been reported in been meiosis, or more rarely from de novo or DS. Major genital anomalies have not inherited unbalanced translocations. The reported by either of two large studies of DS Department of androgen insensitivity syndromes are rare X males.67 Histology of the testis in DS usually Paediatrics, linked single gene disorders of phenotypic shows markedly decreased spermatogenesis.'° University of or of androgen de- Cambridge, sexual development associated with a male Sparse poor development Addenbrooke's (46,XY) karyotype.' AIS is characterised by a pendent hair (pubic, axillary, beard) has been Hospital, Cambridge female or ambiguous genital phenotype in a reported in DS.36 Testosterone levels have been CB2 2QQ, UK to be normal in DS men.36 However, R B Viner 46,XY male with normal testicular histology found N Shimura and normal testosterone production. Cases the finding of frequently raised FSH and LH B D Brown show either complete (CAIS) or partial (PAIS) levels has been interpreted as evidence of mild I A Hughes 11 insensitivity to androgen action. The former gonadal dysgenesis in DS.7 1 In the only study Department of presents with a normal female phenotype of DS male children, Hsiang et a17 reported Medical Genetics, whereas the latter presents in a spectrum from that five of 27 had raised LH levels, and eight University of of 27 showed raised FSH levels. Cambridge, apparently virilised females to undervirilised Addenbrooke's males. AIS is a phenotypically heterogeneous syn- Hospital, Cambridge We report three cases of Down syndrome, drome, and the known molecular defects in CB2 UK 2QQ, two with features of a PAIS phenotype based the androgen receptor (AR) responsible for A J Green 14 on minimal clitoral enlargement, and one with androgen insensitivity are diverse in nature.'3 Corrrespondence to: has Studies of androgen binding in genital skin Professor Hughes. a CAIS phenotype. Androgen insensitivity not been in Down syn- fibroblasts ofAIS patients have defined patients Received 29 September previously reported 1995 drome. However, studies have reported im- as either androgen receptor positive or AR Revised version accepted and mildly impaired gonadal negative. The majority of CAIS patients are for publication paired fertility,2 27 February 1996 function in a high proportion ofmales with DS. receptor negative. In contrast, no clear cut Down syndrome in association with features of the androgen insensitivity syndrome 575

". Table 1 Clinical features ofAIS cases .- _z Case 1 Case 2 Case 3 Date of birth 29.12.84 1.7.94 14.9.78 Genitalia J Med Genet: first published as 10.1136/jmg.33.7.574 on 1 July 1996. Downloaded from Phenotype PAIS PAIS CAIS Gonads Labial testes Labial testes Labial testes Clitoromegaly Mild Mild No Urethral opening Perineal Perineal Perineal Scrotum/labia Unfused Unfused Unfused Vaginal orifice Present Hypoplastic Present Uterus Absent Absent Absent Associated conditions Nil Right diaphragmatic Eisenmenger syndrome hernia-Morgagni type and patent ductus arteriosus; left talipes

relationship between clinical phenotype and AR binding exists in PAIS patients; the majority of cases show normal receptor binding, al- though a small subset show qualitative abnormalities in AR binding.'5 When binding is negative or qualitatively abnormal, mutations are invariably identified in the exons encoding the ligand binding domain of the AR gene, whereas normal AR binding in CAIS is invariably associated with mutations affecting the DNA binding region. A number of cases, par- Appearance of the external genitalia in case 2 ticularly PAIS, show normal AR binding and no detectable abnormality in the AR gene.""'4 This finding suggests that hitherto un- Normal androgen production and metabolism, genes may be in re- recognised involved the and normal testicular histology was found in of in gulation androgen sensitivity humans. cases 1 and 2 (table 2). Investigation of case 3 was limited by the associated complex cardiac problems. Interestingly, a 46,XY sib had isol- Case reports ated perineal hypospadias so a genital skin Cases were drawn an es- from AIS database fibroblast line was established at the time of tablished at the of Department Paediatrics, surgical repair to measure AR binding. An- University of as a result of Cambridge, partly drogen binding activity was measured by a a UK wide survey of undertaken AIS through whole cell binding assay using genital skin the auspices of the British Paediatric Associ-

fibroblasts."6 Androgen binding was normal in http://jmg.bmj.com/ ation Surveillance Unit. of the Ascertainment cases 1 and 2, and in the 46,XY sib of case 3 cases was based upon postnatal chromosomal (table 3). All three cases were reared as females. analysis performed because of clinical features Bilateral gonadectomy was performed on case of Down 1 syndrome. Cases and 2 (figure) had 1 at 11 years, and bilateral gonadectomy and slightly abnormal genitalia noted at birth, while vulvovaginoplasty on case 2 at 2 months of case 3 had normal female genitalia (table 1). age. None of the cases has received androgen All cases were non-disjunctional trisomy 21 or oestrogen therapy. with karyotypes 47,XY, + 21. A on September 27, 2021 by guest. Protected copyright. diagnosis of DNA was obtained in case 1 and the sib of AIS was based upon male karyotype and the case 3 from genital skin fibroblasts and from results of subsequent investigations. Two cases peripheral blood lymphocytes in cases 2 and on balance had features consistent with a PAIS 3. Mutation screening of the AR gene was phenotype but only very minimal signs of vir- carried out by PCR-single strand conformation ilisation, and one case had a typical CAIS polymorphism (SSCP) analysis ofDNA as pre- phenotype. viously published.'7 All eight exons of the AR gene which encode the ligand binding, DNA Investigations binding, and transcriptional activation domains These included measurement ofandrogen pro- were analysed. There was no evidence of a duction and metabolism after HCG stimu- band shift to indicate the presence of an AR lation, basal gonadotrophin concentrations, gene mutation in any of the three cases; in testicular histology, assessment of AR binding particular the two exons encoding the DNA in genital skin fibroblasts, and DNA analysis. binding domain of the AR were normal.

Table 2 Endocrine investigations and gonadal histology Case 1 Case 2 Case 3 HCG simulation test 500 units HCG single dose 500 units HCG for 3 days Not done Pre Post Pre Post Testosterone (nmol/l) 12 28 7-8 9-4 Dihydrotestosterone (nmolIl) 2-2 1-8 0 4 0-53 Androstenedione (nmol/l) 2-8 5-4 LH (U/1) 7-2 <1 FSH (U/1) 2-2 1.0 Urinary steroid profile Not done Normal Not done Histology Normal testes Normal testes Not done 5765iner, Shimura, Brown, Green, Hughes

Table 3 Androgen binding in genital skin fibroblasts under-reported in DS, as minor genital an- Case 1 Case 2 Case omalies such as mild clitoromegaly or simple 3 hypospadias are more likely to be disregarded Bmax 1136 949 Not done* in DS than in the general population. (normal range 1342-8+419 x 10 DNA) J Med Genet: first published as 10.1136/jmg.33.7.574 on 1 July 1996. Downloaded from -8 mol/4g One possible explanation is the presence of Kd 0-71 1.0 an SRY box (Sox) gene on chromosome 21, (normal range + 0-252 x 1-08 10"-'° mol/l) given the recent finding of an association be- Bmax, receptor concentration. Kd, binding affinity. tween the Sox-9 gene and sex reversal in cam- * 46,XY sib with perineal hypospadias had normal androgen binding. pomelic dysplasia.24 Sox genes are closely related to the SRY gene that determines testis development in mammals. SRY exerts its function through transcriptional control of un- Discussion identified genes "downstream" in the testis Three cases of Down syndrome with a pre- development pathway, and defects in SRY have dominantly female phenotype are described been found to result in XY females with gonadal with a 47,XY,+21 karyotype, normal testos- dysgenesis.'524 It is postulated that, like SRY, terone production and metabolism, and normal Sox genes may act as transcription factors in testicular histology in two of three cases. There sex development control pathways, and some was no evidence of a defect in steroid bio- Sox genes have been identified as involved in synthesis based on the adequate androgen re- sex differentiation.'8 The phenotypic spectrum sponse to HCG stimulation. Furthermore, from a normal female phenotype and minor gonadal dysgenesis possibly associated with a virilisation as described in these cases to the defect in a testis determining gene such as minor undervirilisation commonly reported in SRY'18 DAX-1,'920 or WT-1,2' is unlikely in male DS may be explained by allelic hetero- view of the normal androgen response to HCG geneity in dosage sensitive Sox related genes and normal testicular histology. Even though on the trisomic chromosomes. 18 25 Further work all three cases had features consistent with the is needed to characterise the defect in gonadal diagnosis of AIS, no defect in the AR gene function in male DS patients and to determine was detected by screening with PCR-SSCP whether chromosome 21 has a role in sex analysis. This technique is a reliable screen determination. based upon our previous work,'7 and sub- We are grateful to the following persons for providing clinical sequently confirmed by direct sequence anal- information relevant to the cases: Dr V Marrian, Consultant ysis (H R Davies, personal observation). Paediatrician, Perth Royal Infirmary, Perth; Dr J A Sill, Con- sultant Paediatrician, St Helens and Knowlsley Hospital, Pre- This cluster is possibly a chance occurrence. scot, Merseyside; Dr P J Howard, Consultant Clinical Scientist, However, the finding ofnormal androgen bind- Merseyside and Cheshire Regional Cytogenetics Unit. Dr N Shimura was supported by a grant from Eli Lilly, Japan, and ing and normal AR gene in one case with a the work was funded by the Wellcome Trust. The help of the typical CAIS phenotype and the other two cases British Paediatric Association Surveillance Unit in identifying cases for further study is gratefully appreciated. at the extreme female end of the PAIS pheno- http://jmg.bmj.com/ 14 typic spectrum is very uncommon-,3 and sug- 1 Patterson MN, McPhaul MJ, Hughes IA. Androgen in- gests that this cluster is more than mere sensitivity syndrome. Hormones, enzymes and receptors. Clin Endocninol Metab 1994;8:379-404. coincidence. While it is interesting that a 46, 2 Sheridan R, Llerena J, Matkins S, et al. Fertility in a male XY sib of case 3 who has complete sex reversal with trisomy 21. JfMed Genet 1989;26:294-8. 3 Smith GF, Berg JM. Down's anomaly. 2nd ed. Edinburgh: also has a severe genital anomaly, the cause in Churchill Livingstone, 1976:40-4. this instance is clearly unrelated to an extra 4 Lang DJ, Dyke DCV, Heide F, et al. Hypospadias and cases urethral abnormalities in Down syndrome. Clin Pediatr chromosome 21. 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