Hypospadias as a novel feature in spinal bulbar muscle atrophy.

Spinal and bulbar muscle atrophy (SBMA) is an X-linked neuromuscular disorder caused by CAG repeat expansions in the androgen receptor (AR) gene. The SBMA phenotype consists of slowly progressive neuromuscular symptoms and undermasculinization features as the result of malfunction of the AR. The latter mainly includes gynecomastia and infertility. Hypospadias is also a feature of undermasculinization with an underdeveloped urethra and penis; it has not been described as part of the SBMA phenotype but has been suggested to be associated with a prolonged CAG repeat in the AR gene. This study includes the first epidemiologic description of the co-occurrence of hypospadias and SBMA in subjects and their male relatives in Swedish population-based health registers, as well as an additional clinical case. One boy with severe hypospadias was screened for mutations in the AR gene and was found to have 42 CAG repeats in it, which is in the full range of mutations causing SBMA later in life. We also detected a maximum of four cases displaying the combination of SBMA and hypospadias in our national register databases. This is the third case report with hypospadias in association with CAG repeat expansions in the AR gene in the full range known to cause SBMA later in life. Our findings suggest that hypospadias may be an under diagnosed feature of the SBMA phenotype and we propose that neurologists working with SBMA further investigate and report the true prevalence of hypospadias among patients with SBMA.

Population based nationwide study of hypospadias in Sweden, 1973 to 2009: incidence and risk factors.

PURPOSE: We studied the incidence of hypospadias in Sweden during a 40-year period to determine if changes were associated with known risk factors. MATERIALS AND METHODS: We analyzed prospective data from nationwide health care and demographic registers collected for all males (1,948,591 total) born in Sweden between 1973 and 2009. The incidence of hypospadias per 1,000 live-born boys was calculated as number of cases divided by total number of births yearly. The association between hypospadias and risk factors was estimated using logistic regression, expressed as odds ratios. RESULTS: The nationwide incidence of boys diagnosed with hypospadias was approximately 4.5 per 1,000 live-born boys until 1990, increasing to 8 per 1,000 boys during the following decade. Mild and severe phenotypes comprised the increase. Boys born small for gestational age (OR 4.34), as a twin (OR 1.8), as a result of in vitro fertilization (OR 1.15), or with parents from Asia (OR 1.45) or continental Europe (OR 1.41) were at increased risk for hypospadias. Multivariate analyses revealed that changes in risk factors did not explain the increased incidence. However, a systematic change in the classification of the diagnosis in registers could not be ruled out. CONCLUSIONS: This nationwide study demonstrates an increased incidence of hypospadias diagnoses in Sweden from 1990 to 1999 that is not attributable to previously known risk factors. The increase includes mild and severe phenotypes, suggesting that shifts in the diagnostic criteria are not the underlying cause.