Duncan's dermatosis: From the "terra firma-forme" to a possible syndromic condition. The story of a dirty disease

Since its first description by Duncan, Tschen and Knox in 1987 in the former Archives of Dermatology (1), “Terra firma-forme dermatosis” has been variously described in medical literature, representing a strange, probably underestimated, cutaneous disease. During the last 40 years, the condition has been recorded as an undesirable as well as unexplained event, occurring mainly in childhood, characterized by a brownish-black appearance of the whole skin, resembling dirt. Recently, authors described several cases of atypical patterns of the disease, sometimes with impressing topographic clinical pictures, evocative for syndromic phenotypes. Thanks to more careful examination of the tegument, often with the aid of non-invasive diagnostic tools, attention to this disease is growing. This brief review summarizes the state of the art on the topic, through an historical overview of what is known of this ‘dirty’ dermatosis.