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Androgen insensitivity syndrome (AIS) is caused by mutations in the gene encoding the androgen receptor (AR). The incidence of AIS is estimated to be 1 in 99,000. Complete androgen insensitivity syndrome (CAIS) is characterized by a 46,XY karyotype with external genitalia that appear typically female and results from mutations that render the androgen receptor non-functional. Partial androgen insensitivity syndrome (PAIS) results from partial loss of function mutations in <em>AR</em>. Rarely, PAIS results from somatic mosaicism for an <em>AR</em> mutation and not from a hypomorphic variant. We present two cases of PAIS due to somatic mosaicism, one caused by a novel nonsense mutation and one caused by a missense mutation previously reported in CAIS. Two patients with atypical genitalia presented to our multidisciplinary clinic for disorders of sex development and sequencing of <em>AR</em> was performed as part of the diagnostic evaluation. In case one, <em>AR</em> sequencing revealed mosaicism for a nonsense mutation, c.1331T &gt; A; p.Leu444Ter. This mutation has not previously been reported, but is presumed to be pathogenic. In case two, <em>AR</em> sequencing revealed a mosaic missense mutation, c.2279 C &gt; A; p.Ser760Tyr, which has previously been reported in CAIS but not in PAIS. Similar phenotypes may result from <em>AR </em>mutations that are present in a mosaic state with full loss of function or hypomorphic mutations that partially impair the function of the protein in either all tissues or in a mosaic state.