ESPE Abstracts (2018) 89 P-P2-370

aDepartment of Pediatrics, Division of Pediatric Endocrinology, UZ Brussel, Jette, Belgium; bDepartment of Medical Genetics, UZ Brussel, Jette, Belgium;

Background: Persistent Müllerian Duct Syndrome (PMDS) needs to be considered in boys (46, XY) presenting with bilateral cryptorchidism or unilateral cryptorchidism associated with an inguinal hernia. Anti-Müllerian hormone (AMH) gene as well as Anti-Müllerian hormone Receptor (AMHR 2) gene mutations have been identified in PMDS boys.

Aim and methods: To report a novel mutation in the AMHR 2 gene in monochorionic diamniotic (MCDA) twin boys with different anatomical presentation of PMDS. The AMHR 2 gene analysis was performed by Sanger sequencing.

Results: After 36 weeks of an uneventful gestation, the MCDA twin brothers were born with a normal birth weight and length. Both consanguineous Turkish parents were healthy, but both their two older daughters had been diagnosed with an unexplained retinitis pigmentosa. Bilateral cryptorchidism without penile abnormalities was noted at birth in both boys. Since intra-abdominal testes were suspected at ultrasound in the first week of life, no further examinations were performed at that moment. At referral to the pediatric endocrinology department at the age of 14 months because of persisting cryptorchidism, both infants had an identical body weight of 7.93 kg (−0.86 SDS) and a body length of 79.5 cm (+0.18 SDS). Physical examination revealed apart from cryptorchidism, a synophrys and slight hypertrichosis in both children. Serum testosterone level increased respectively up to 5.98 μg/l and 6.21 μg/L and serum dihydrotestosterone to 0.50 μg/L and 0.56 μg/L three days after single dose of 2500 IU of hCG. Boy 1 had a normally developed scrotum and a penile length, but at laparoscopic exploration, a crossed fused ectopia of the left testis was found. Boy 2 had an underdeveloped scrotum and at surgical exploration a hypotrophic vas deferens without testicular fusion and a remainder of a fallopian tube was found. Additional genetic investigations demonstrated a normal 46, XY karyotype and a homozygous mutation c.1473C>G p.(Asp491Glu) in the AMHR2 gene in both boys. This variant is classified as likely pathogenic on the base of prediction programs and a pathogenic effect of a known other variant within the same amino acid (Asp491His).

Conclusions: A novel but similar AMHR 2 gene mutation was found in non-identical twin brothers, presenting with a different anatomical variant of PMDS, a crossed testicular ectopia in one boy and a female Mullerian remnant structure in the other.

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