Progressive hyperpigmentation and generalized lentiginosis without associated systemic symptoms: a rare hereditary pigmentation disorder in south-east Germany

Familial progressive hyperpigmentation is rarely described in the literature. We report on five patients from three different families presenting with a peculiar progressive pigmentary disorder. The patients show a progressive diffuse, partly blotchy, hyperpigmentation, intermixed with scattered small hypopigmented macules, a few large hypopigmented areas, occasional café-au-lait spots and, most remarkably, a generalized lentiginosis. Histology revealed different degrees of basal layer hyperpigmentation and pigment incontinence, also in the spots appearing hypopigmented. Ultrastructural analysis showed a normal mode of Caucasian-like melanogenesis with varying content of regular melanosome complexes within the keratinocytes. All families are clustered in a small area around the town of Teublitz in south-east Germany with about 20,000 inhabitants, suggesting a genetic founder effect. Pedigree analysis is compatible with an autosomal dominant mode of inheritance with variable penetrance. Only a few similar, but not identical, cases have been reported in the past. This cluster of cases may therefore represent a rare and perhaps novel variant of a familial progressive disorder of hyperpigmentation.