Vom Genotyp zum Phanotyp. Molekulargenetische Diagnostik bei Intersexualitat

The determination of the genetic background of sexual development has not only assisted in the explanation of intersex disorders, but also in the diagnosis and clinical management of affected individuals. The possibilities and limitations of molecular genetic studies can be illustrated by the example of androgen insensitivity syndromes. The search for the underlying mutations within the androgen receptor gene is technically possible even for large numbers of patients. The characterization of mutations can be performed with high specificity and sensitivity. While large gene defects are associated with complete loss of function of the receptor, point mutations with subsequent amino acid changes are responsible for the phenotypic variability of the disease. Type and location of the amino acid substitution may influence the clinical appearance of the individual patient, but the phenotype can be highly variable even with the same underlying mutation. This is probably due to regulation mechanisms within the cell of which the androgen receptor is only one, although important, part. Therefore, results of molecular genetic testing have to be interpreted only in connection with clinical and laboratory findings. Further research will focus on the elucidation of the cellular mechanisms of androgen action in order to introduce the results into the clinical management of patients with androgen insensitivity.