Terra Firma Forme Dermatosis – a Report of two Cases and a Review of the Literature

Abstract

Terra firma-forme dermatosis (TFFD) or Duncan’s dirty dermatosis is a bizarre, acquired, and idiopathic dermatosis. It is characterized by its asymptomatic, yellowish, or brownish dirt-like lesions, resistant to usual washing with soap and water, but disappearing when rubbed with 70% ethyl alcohol or isopropyl alcohol. Swabbing with alcohol is both diagnostic and therapeutic means for this disorder. We present two boys, aged 14 and 11, with asymptomatic brownish, dirt-like lesions on the chest and forearms, respectively. Skin lesions were continuously present for more than a month. Both of the patients had usual hygiene habits. The diagnosis of TFFD was confirmed by rubbing with 70% ethyl alcohol which led to disappearance of the lesions. TFFD often causes much concern in patients and parents of affected children. Since its clinical picture is similar to some other dermatoses, the disease can be misdiagnosed. Therefore, it is important to recognize this dermatosis in dermatological and pediatric practice in order to explain the benign nature of the disease to patients and to avoid unnecessary diagnostic tests.

Terra firma‐forme dermatosis: a systematic review

“…The title and abstract of the 102 items were screened, and 69 were considered eligible for full‐text assessment. Of the 69 studies, 64 were included in the systematic review 1–63 . The studies were published between 1987 and 2020.…”

“…Overall, the records of 22 patients reported a diagnostic pitfall prior to the diagnosis of TFFD (Table 4). The two most common misdiagnoses were AN 14,25,35,39 and mycosis 11,16,27,34 (each accounting for 31.8% of cases), followed by eczema (including atopic eczema in 1 case, 18.2%), 14,47 lichen simplex chronicum 46 (4.5%), vulgar ichthyosis 16 (4.5%), pseudo‐acanthosis nigricans 30 (4.5%), and atypical nevus 48 (4.5%).…”