Universalis dyschromatosis is a rare genodermatosis. Melanogenesis dysfunction appears to be the main etiology. We report two cases, discussing the clinical features, diagnosis and etiology of this disease.A 21-year-old man was referred for a mixture of achromatic and hyperchromatic lesions that had progressed on sun-exposed skin areas since birth. The histopathologic study evidenced increased melanin content in the basal cell zone but no changes in the aspect or the number of melanocytes. The second case was a 20-year-old man who presented the same clinical features. His brother also had these lesions. A scotch test and a Wood light test were negative.Universalis dyschromatosis is a generalized leukomelanoderma. The familial nature of the disease in our second case points out the genetic component. Recent ultrastructure studies have demonstrated the melanogenesis dysfunction involved. The location of the lesions on sun exposed areas points out to the role of ultraviolet light. In Tunisia, Xeroderma pigmentosum is the main differential diagnosis of universalis dyschromatosis.