[Chromosome 9P deletion: Gonadal dysgenesis associated with mental retardation and hypoplasia of the corpus callosum: A contiguous gene syndrome?]

Background: Many genes are involved in testicular differentiation. The alterations of these genes are responsible for sexual differentiation disorders with 46 XY karyotype.

Case: We report the case of a newborn who had an interscrotal hypospadias, palpable gonads and hypoplastic penis. Karyotype 46 XY. Abdominal ultrasound revealed testes and absence of Müllerian remnants. There was a good response to the short gonadotrophin test. At one year he had signs of psychomotor retardation and hypotonia. The magnetic resonance revealed frontal-temporal atrophy and a decrease in the corpus callosum. Testicular biopsy was compatible with gonadal dysgenesis. A preoperative cystography showed a vaginal remnant. Due to the presence of a sexual differentiation disorder, psychomotor retardation and facial dysmorphism, we requested a high-resolution karyotype: deletion 46, XY, del (9p) (p23-pter). Ish tel (9p-).

Discussion: Many genes are involved in testicular differentiation, some of which also affect the development of other tissues. In the short arm of chromosome 9, two genes, DMRT1 and DMRT2, are involved in sexual differentiation. Their alterations have also been described as causing mental retardation. In the evaluation of 46,XY disorders of sex differentiation, the accompanying signs are very important for guiding the genetic study.