Evidence for genetic heterogeneity in male pseudohermaphroditism due to Leydig cell hypoplasia

Leydig cell aplasia or hypoplasia is a rare form of male pseudohermaphroditism resulting from inadequate fetal testicular Leydig cell differentiation. Affected individuals presented a wide phenotypic spectrum, ranging from complete female external genitalia to males with micropenis. Recessive mutations in the LH receptor gene have been identified as responsible for the condition. The majority of these mutations are point mutations and have been located in exon 11 of the gene. In this study, we report the molecular characterization of the LH receptor gene in three siblings with Leydig cell hypoplasia. After sequencing the 11 exons of the gene, no deleterious mutations were detected in any patient. However, we identified a previously described polymorphism in exon 11. In patients 1 and 3 DNA sequencing revealed a C to T substitution at nucleotide 1065; both patients were homozygous GAT/GAT at codon 355. In contrast, patient 2 was homozygous GAC/GAC, whereas the father and one unaffected sister were heterozygous GAC/GAT at this polymorphic site. These results exclude that Leydig cell hypoplasia in this family is due to a mutation in the LH receptor gene and provide evidence that defects in other loci may also result in failure of Leydig cell differentiation, demonstrating, for the first time, that Leydig cell hypoplasia is a genetically heterogeneous condition.