Extensive terra firma forme dermatosis [TFFD]: A rare presentation.

A 19-year-old female presented with asymptomatic, dark colored, gradually progressive lesions on her chest and thighs since the past 1 year. The patient gave a history of adequate personal hygiene but was not able to clear off the lesions with soap and water. Cutaneous examination revealed multiple, bilaterally symmetrical, brown-black, verrucous papules overlying hyperpigmented plaques on the chest extending up to the upper part of abdomen [Figure 1a and b]. Similar lesions were noted over the medial aspect of both thighs. We considered verrucous epidermal naevus, lichen amyloidosis, and acanthosis nigricans and proceeded to biopsy the lesional skin. To our surprise, preparing the skin by cleaning with spirit led to removal of pigmentation, exposing normal skin beneath [Figure 1c and d]. Histopathology revealed a dilated follicular infundibulum, prominent lamellar hyperkeratosis with focal areas of whorled orthokeratosis and keratin globules in the stratum corneum along with a sparse inflammatory infiltrate in the dermis [Figure 2a]. Periodic acid Schiff stain revealed a few vellus hair shafts with pityrosporum spores [Figure 2b]. Fontana Masson stained sections showed increased melanin in the basal layer. A diagnosis of terra firma forme dermatosis (TFFD) was established and forceful rubbing of the skin with isopropyl alcohol soaked gauze pads achieved a complete cure. The patient was advised to reapply isopropyl alcohol and clean her skin in case of recurrence.

Figure 1

(a and b) Bilaterally symmetrical brownish-black verrucous papules overlying hyperpigmented plaques on the chest and well-defined hyperpigmented patches with intervening areas of normal skin on the medial aspect of thighs (c and d) Complete removal of pigmentation upon forceful rubbing with 70% isopropyl alcohol

Figure 2

(a) dilated follicular infundibulum, prominent lamellar hyperkeratosis with focal areas of whorled orthokeratosis and keratin globules in stratum corneum (H and E, x10); (b) A few vellus hair shafts with pityrosporum spores. (PAS, x40)

TFFD is an acquired, benign disorder of keratinization characterized by retention hyperkeratosis presenting as dirt like plaques, despite normal hygiene.[1] It was first reported by Duncan et al.[2] in 1987, hence called “Duncan's Dirty Dermatosis”.

The condition is marked by a delay in the keratinocyte maturation, retention hyperkeratosis and melanin retention with sustained accumulation of sebum, sweat, corneocytes, and microorganisms.[3] It is mostly seen in patients with normal hygiene.[3] Most patients present during the warm period of the year, some having experienced intense sun exposure during summer. No familial characteristic has been reported.[4]

It affects all age groups (age range: 3 months to 72 years) and both genders.[2] The usual sites of involvement include face, neck, trunk, or ankles, although unusual sites such as scalp, lips, chest, axilla, back, umbilical area, pubis, arms, and legs have been reported. Rarely, palpable verrucous or papillomatous plaques, reticulate patches, and focal slight scaling have been observed.[2] The dermatosis often clears after rubbing with a pad soaked in 70% alcohol.[1] In many cases, aggressive rubbing using substantial shearing force is required to remove the brown pigmentation.[5]

Differential diagnosis includes acanthosis nigricans, confluent and reticulate papillomatosis of Gougerot and Carteaud, pityriasis versicolor, epidermal nevi, dirty neck syndrome of atopic dermatitis, and dermatitis neglecta (DN).[1] TFFD is distinguished from DN by the presence of adequate hygiene, absence of cornflake-like brownish scales, and successful removal of pigmentation with isopropyl alcohol in the former and effective clearance of lesions with soap and water in the latter.[1] Usually the discoloration does not recur. However, if it does, one may simply apply alcohol once a week to keep the skin clear.[1] This case has been presented for its atypical verrucous appearance, extensive involvement and the uncommon sites of involvement.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.