46,XX male disorder of sexual development
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The sexual phenotype is determined by the presence or absence of the Y chromosome in the karyotype of the embryos. However, the vast majority of 46,XX males carry a portion of the Y chromosome, as a result of recombination between the distal portions of the short arms of the X and Y chromosomes during male meiosis. These individuals develop male genitalia in the absence of the Y chromosome. In fact, on the basis of the SRY (sex-determining region of Y) gene, this condition may be divided into two groups: SRY positive (which accounts for 90% of 46,XX males) and SRY negative.

A previously healthy 13-yr-old male adolescent was referred to the Pediatric Endocrinology outpatient clinic due to progressive bilateral gynecomastia. In regard to the features of sexual development, he presented marked bilateral and symmetric gynecomastia, with palpable breast tissue of nearly five centimeters. The male external genitalia appeared normal, with a penis size of 13 centimeters and thick black pubic hair at its base corresponding to stage III on the Tanner scale. The testicles were palpable in the scrotum, both small for his age, with a volume of approximately 2 mm.

The endocrinological study revealed high levels of both gonadotropins, with a luteinizing hormone level of 20.04 mUI/mL and follicle-stimulating hormone level of 59.17 mUI/mL. In addition, a low testosterone level of 2.33 ng/mL was recorded, with undetectable androstenedione. The sex hormone-binding globulin levels were high, 94.5 nmol/L, and the estradiol levels were 19.8 pg/mL, with 2.38 ng/mL 17-hydroxyprogesterone. These results were consistent with the hypergonadotropic hypogonadism diagnosis.

The bone age was assessed using a hand and wrist X-ray and matched his chronological age. The chromosomal analysis revealed an apparent 46,XX karyotype. Fluorescence in situ hybridization (FISH) revealed that the SRY gene locus was translocated to the short arm of the X chromosome.

A multidisciplinary approach, including psychological support and genetic counseling, is ideal for the management of these patients. Neoplastic transformation of the dysgenetic gonads has been described in several cases, and hence self-examinations and regular ultrasounds are commonly advised.

Source: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6958519/
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