Homozygosity for a Novel INHA Mutation in Two Male Siblings with Hypospadias, Primary Hypogonadism, and High-normal Testicular Volume

Background: The human INHA gene encodes the inhibin subunit alpha protein, which is common to both inhibin A and B. The functional importance of inhibins in male sex development, sexual function, and reproduction remain largely unknown.

Objective: We report for the first time two male siblings with homozygous INHAmutations.

Methods: The medical files were examined for clinical, biochemical, and imaging data. Genetic analysis was performed using next-generation and Sanger sequencing methods.

Results: Two brothers complained of gynecomastia, testicular pain, and had a history of hypospadias. Biochemistry revealed low serum testosterone, high gonadotropin and anti-Mullerian hormone, and very low/undetectable inhibin concentrations, where available. Both patients had azoospermia in the spermiogram. We have identified a homozygous 2 bp deletion (c.208_209delAG, R70Gfs*3) variant, which leads to a truncated INHA protein in both patients, and confirmed heterozygosity in the parents. The external genital development, pubertal onset and progression, reproductive functions, serum gonadotropins, and sex hormones of mother and father, who were heterozygous carriers of the identified mutation, were normal.

Conclusion: Homozygosity for INHA mutations causes decreased prenatal and postnatal testosterone production and infertility in males, while the heterozygous female and male carriers of INHA mutations do not have any abnormality in sex development and reproduction.