During the evaluation of a healthy 7-year-old boy, an asymptomatic brown “dirt-like” rash is found on the anterior neck. It has progressed over the last 2 months and does not clear with routine bathing and aggressive scrubbing by his mother with soap and water.
You are asked to evaluate a healthy 7-year-old boy with an asymptomatic brown “dirt-like” rash on the anterior neck (Figure 1). It has progressed over the last 2 months and does not clear with routine bathing and aggressive scrubbing by his mother with soap and water. After wiping with 70% isopropyl alcohol in the office, the brown pigment readily disappeared and mild erythema secondary to rubbing was noted confirming the diagnosis of Terra firma-forme dermatosis (Figure 2).
Terra firma—forme dermatosis
Terra firma-forme dermatosis (TFFD) is an acquired, benign, idiopathic dermatosis first described by Duncan and his colleagues in 1987. The name is derived from the Latin phrase ‘terra firma’ which refers to ‘dry land’. It is a rare type of keratinization disorder characterized by an asymptomatic brownish gray or black dirt-like patch that cannot be removed with soap and water and cleansers, but needs wiping with isopropyl alcohol or ethyl alcohol. The highest prevalence was found among prepubertal children (88.6%) with an average age of onset of 10.4 ±7.5 years, ranging from 3 years to 72 years.1 Commonly, the skin on the trunk and neck was involved, about a quarter of all patients showed involvement of the extremities, and in less than 3% over the head. Most of the lesions are solitary: However, in about 30% several lesions were found. It is often underreported.
Exact etiopathogenesis is not well understood. It is believed that the lesions arise as a result of a delay in the maturation of keratinocytes, with melanin retention and a sustained accumulation of sebum, sweat, corneocytes, and microorganisms in regions in which the skin is more sensitive to trauma and hygiene measures are less vigorous (neck, navel, flanks) leading to insufficient exfoliation and the formation of a highly adhesive, compact dirt like scale.2 It explains the hyperkeratosis and hyperpigmentation clinically seen in TFFD.
Histopathological examination, rarely required, shows prominent lamellar hyperkeratosis with whorls, keratotic plugging of follicular orifices, keratin globules in the stratum corneum, papillomatosis, and sharp invaginations between the papillae, increased melanin pigment in the basal layer, and minimal lymphocytic liquefaction. A Fontana-Masson stain shows focally increased melanin pigment in the basal layer of the epidermis. Periodic acid Schiff stain revealed a few vellus hair shafts with pityrosporum spores.3 Parakeratosis is not observed.4
Terra firma-forme dermatosis is characterized by accumulation of hyperpigmented, hyperkeratotic and verrucous scale and/or crusts. Rarely palpable verrucous or papillomatous plaques, reticulated patches, and mild focal scaling have been observed.
Dermoscopy shows large, polygonal, plate-like, brown scales in a mosaic, cobblestone, or tie like pattern interrupted in furrows. Diagnosis can be confirmed by rubbing the lesion with an alcohol-soaked pad or cotton ball, which results in resolution of the lesions.5 This is known as the skin modified by alcohol rubbing test.5
Dermatosis neglecta typically affects individuals of any age with neglected hygiene.6 The brownish, hyperkeratotic, verrucous crusts and corn flake-like scales, often symmetrical, result from progressive accumulation of sebum, cellular debris, keratin, sweat, and exogenous impurities. Lesions can be removed with soap and water or an alcohol swab or cotton ball. Histopathologically shows lamellar hyperkeratosis without any whorled hyperkeratosis.
Confluent and reticulated papillomatosis (CARP): CARP is an acquired icthyosi-form dermatosis characterized by persistent, asymptomatic, dark, scaly macules and patches that tend to be confluent in the center and reticulated at the periphery and localized predominantly on the trunk.7 The lesions are red to brown, slightly verrucous papules on chest, back, neck, chin, arms, axillae. It may respond to topical therapy with topical calciportiol or retinoids but responds best with oral doxycycline.
Post-inflammatory hyperpigmentation also known as post inflammatory melanosis, develops as a sequela of a variety of insults to the skin, such as atopic dermatosis, acne vulgaris, trauma, chemical/physical injuries. It presents as hyperpigmented macules/patches in the preceding inflammatory dermatosis or injury. The color tends to be tan to light brown if the excess pigment is within the epidermis. If the excess pigment is in the dermis, the color is usually blue or dark gray.8 Acanthosis nigricans consists of dark, velvety thickening of the skin, usually on the nape and sides of the neck, as well as the Axillae and inner thighs. The lesions typically presents in a symmetric fashion. There is no melanin deposition. Rather, the pigmentation is mainly due to hyperkeratosis. The condition is most commonly caused by obesity, metabolic syndrome, diabetes mellitus. The hyperpigmentation or dust cannot be removed by washing with soap and water or alcohol swab or cotton ball.
The condition of TFFD can be treated by forceful rubbing with gauze immersed into 70% isopropyl alcohol/ethyl alcohol to remove the lesions, which is diagnostic and therapeutic too. This procedure possibly determines protein denaturation, interfering in the cell metabolism and diluting lipoprotein membranes,9 thus avoiding blood tests and skin biopsies. Mild inflammation, erythema, stinging-like sensation are reported after vigorous rubbing of repeated applications. The skin should be washed with soap and water after using alcohol, considering the possible symptoms of intoxication as drowsiness, lethargy, respiratory depression, mucosal irritation and others, especially in children. Other keratolytic agents like salicylic acid 5%/20% in alcohol base, 30% Urea, 12% Ammonium lactate showed similar efficacy after application for 2 weeks on the affected area, without any irritation/erythema.10 Moisturizing the affected skin is important to prevent xerosis after regular treatments with isopropyl alcohol. Recurrence is unusual after proper treatment. Rare recurrences can also be treated weekly with alcohol wipes or topical keratolytic agents.
At follow-up 3 months later there were no signs of recurrent pigmentation, and he did not require any cleaning with alcohol wipes.
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6. Sasaya EMK, Ghislandi C, Trevisan F, et al. Dermatosis neglecta. An Bras Dermatol. 2015; 90(3 suppl 1):59 – 61
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8. Leung, AKC, Barankin B, Leung, AAM, Lam JM. A hyperpigmented patch that remains despite washing with soap and water. Consultant 360. 2018;5 (11):309 – 312, 315
9. Sasaya EMK, Ghislandi C, Trevisan F, Ribeiro TB, Mulinari–Brenner F, Gaiewski CB. Dermatosis neglecta. A Bras Dermatol. 2015;90(51):58- 60
10. Chun SW, Lee SY, Kim JB, Choi HM, Ro BI, Cho HK. A case of Terra firma – forme dermatosis treated with salicylic acid alcohol peeling. Ann Dermatol. 2017;29(1):83- 85