[From gene to disease; androgen receptor gene, androgen insensitivity syndrome, and spinal and bulbar muscle atrophy].

Androgen insensitivity is an X-linked disorder of male sexual differentiation resulting from a defective androgen receptor. Spinal and bulbar muscular atrophy (Kennedy's disease) is an X-linked disease, resulting from expansion of the polyglutamine stretch in the N-terminal part of the androgen receptor. Mutation analysis confirms the clinical diagnosis of androgen insensitivity and enables carrier detection and prenatal diagnosis. Kennedy's disease, with its diagnostic problem of clinical variability, is diagnosed or excluded when an expanded CAG-repeat is present or absent in exon 1 of the androgen receptor. Molecular testing can be used for carrier detection and genetic counselling.