Unusual neurocutaneous syndromes.

During the last several decades, the number of these rare heterogeneous disorders described as neurocutaneous syndromes has significantly increased. The criteria for inclusion have become more general, although most of the disorders have dysplastic features, many do not have a tendency for tumor formation. Further, not all of these disorders are heritable and some are reported in only one or two families. Nonetheless, there is some merit for the clinician, geneticist, and embryologist to consider these anomalies of embryologic development on some common ground. Knowledge of these syndromes is important to correctly establish the diagnosis and prognosis. In cases of the heritable disorders, genetic counseling is essential. Finally, these disorders are of theoretic importance to all biologists, as the exchange of information will be essential to ultimately unravel the reasons for their cause.