Terra firma-forme dermatosis: wipe first.

Abstract

Editor, A 3-year-old boy was seen for milky brown lesions on the abdomen that had been present for three weeks. On physical examination, pigmented patches on the abdomen, along with the scar of a linear incision that referred to a previous intestinal operation, were apparent (Fig. 1a). The child had not received any treatment for the skin lesions. The mother of the patient denied the use of any chemicals or creams, or any trauma to the area of involvement. The subject's past medical history was unremarkable for systemic or dermatologic diseases. We were told by his mother that the boy was used to showering twice per week on a regular basis. There were no similar lesions in any member of his family. We suspected a diagnosis of terra firma-forme dermatosis (TFFD) and wiped the pigmented patches with a gauze pad saturated with 70% ethyl alcohol. After the procedure, the wiped area cleared completely (Fig. 1b). A 3-year-old girl presented with a 5-month history of persistent pigmented patches on the flexor aspects of the left arm and both knees (Fig. 2a). She had not received any treatment for these lesions until the current presentation. She had no history of any systemic or dermatologic disorders. The mother of the girl denied the application of any chemicals or creams, or any trauma to the affected areas. We were told that the patient was used to showering two or three times per week. We diagnosed the lesions as TFFD. The diagnosis was confirmed by wiping the lesions with 70% ethyl alcohol-soaked gauze pads. The lesions were easily removed, leaving mild, dirt-like scales (Fig. 2b). Terra firma-forme dermatosis, known also as “Duncan's dirty dermatosis,” is a rarely reported keratinization disorder of unknown etiology.1, 2 It is proposed to occur as a result of abnormal and delayed keratinization, incomplete development of keratin squames, and the retention of melanin in certain areas of the skin.2, 3 Accumulation of the residues of sweat, scales, sebum, emollients, bath oils, and soaps may also contribute to its pathogenesis.3, 4 The condition usually manifests as asymptomatic, dirt-like, slightly papillomatous, hyperpigmented patches or plaques primarily on the neck and trunk. It can be seen at any age and in both genders.1, 2, 4 Lesions are resistant to regular washing with soap but are easily removed by wiping with ethyl or isopropyl alcohol. Cases of TFFD can be both diagnosed and treated using this simple procedure. Recurrence is unusual after treatment.5 Differential diagnoses include dermatosis neglecta (DN), confluent and reticulate papillomatosus of Gougerot and Carteaud, pityriasis versicolor, and acanthosis nigricans.1, 3-7 Whether TFFD and DN are different diseases or diverse types of the same disease is still controversial. In DN, the patient neglects to wash the lesion for any of a number of different reasons, the most common of which is poor hygiene. Both TFFD and DN lesions can be treated completely by wiping with alcohol; however, DN lesions can also be cleared by washing with soap and water.3, 7 The lesions of any of the other disorders included within the gamut of the differential diagnosis cannot be cleared by wiping with alcohol or by washing. Although both of our patients had regular washing habits, their lesions were gradually growing. We were able to remove the lesions easily with alcohol. To the best of our knowledge, only approximately 60 cases of TFFD have been reported in the literature until now. Lack of awareness of this condition, even among dermatologists, is likely to be the major reason for the under-reporting of the entity. Unnecessary skin biopsies and batteries of blood tests can be avoided if TFFD is retained in the differential diagnosis of such presentations.