Ashy dermatosis, or "Tyndall-effect" dermatosis.

A 59-year-old man with ashy dermatosis is presented; the classification and diagnosis of this disease is discussed. Ashy dermatosis presents two main clinical aspects: the ashy-color maculae, and the involvement mainly in darker-skinned patients often from Latin America and Asia. The blue-grey color can be explained by the Tyndall effect because of the melanin found in the dermis. Bluish dermal melanocytoses are also more common in these same racial and ethnic groups. Perhaps the particular size and distribution of melanosomes in these groups predisposes them to development of ashy dermatosis.