This disorder, also termed spinal and bulbar muscular atrophy, is a debilitating, neurodegenerative condition that begins by age 30 and consists of muscle cramping and atrophy as well as testicular atrophy. The genetic basis for the disease is not exactly a mutation but a variation in the length of the AR gene in a specific region (transcriptional activation domain) that results in decreased androgen-binding ability. The AR gene on Xq has eight exons and it is clear that a critical region of CAG-nucleotide repeats, usually 15-30 in number, exists in exon 1. Elongation of the number of CAG repeats in this region to more than 50 generally results in clinically apparent disease (Kupker et al., 1999). The clinical infertility resembles that due to mild androgen insensitivity and may include gynecomastia in addition to testis atrophy. Interestingly, some affected patients may have only mild oligo-zoospermia and as such may be able to conceive naturally or with ICSI. Men, fertile at an early age, may actually experience a significant reduction in their sperm counts with advancing age and disease progression. Importantly, affected couples should be counseled about the phenomenon of genetic 'anticipation' that occurs with this disorder, in which offspring may inherent an even larger number of CAG-nucleotide repeats than that of the parent. Clinically, this translates into a more severe disease phenotype that is manifest earlier in life. Specialized laboratories offer exon 1 CAG-nucleotide repeat analysis of the AR gene.
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