terra firma-forme dermatosis

Terra Firma-Forme Dermatosis

Megha D. Patel, BS
Stephen Schleicher, MD
Volume 15 - Issue 2 - February 2016

A 13-year-old Caucasian female presented with a rash on her neck for approximately 3 weeks in duration. She was asymptomatic but complained that cleaning her skin with soap and hot water did not lead to improvement of the rash. The patient had no known medical conditions and was not on any medications.

Physical examination of the girl revealed a hyperpigmented patch on her anterior left neck (Figure). The rash was wiped off in the office with an alcohol swab. 

Physical exam revealed a hyperpigmented patch on the patient's anterior left neck

The girl and her mother received a diagnosis of terra firma-forme dermatosis (TFFD).

TFFD is a benign disorder of keratinization that affects children and young adults.1 The most prominent clinical presentation of TFFD is characterized by brown-gray, velvety, pigmented patches or plaques that resemble dirt.2 In children, it usually presents on the neck but can present on the face or trunk or unusual sites such as the scalp or pubic region.2-4 

Patients typically present during the spring or summer after sun exposure.5 Parents complain of a brown dirty rash that cannot be washed off with normal soap or routine cleansers.3,4 

The etiology of TFFD is unknown, but it is not due to a lack of personal hygiene.6 Speculations into the etiology of TFFD suggest that it is a dermatologic disorder of abnormal and delayed keratinization, causing altered maturation of keratinocytes and retention of melanin.2,5

Definitive confirmation of TFFD is through forceful rubbing with 70% isopropyl alcohol or ethyl alcohol, which reveals the normal skin underneath.2 Further testing and laboratory workup is unnecessary; however, in some cases, the diagnosis can be difficult because TFFD can be confused with other dirt-like dermatosis, such as acanthosis nigricans, dermatosis neglecta, and confluent and reticulated papillomatosis.2,7 

In such cases, a biopsy and histopathologic analysis can be performed. Histopathology reveals lamellar hyperkeratosis with focal orthokeratosis in whorls but absent parakeratosis.4,6  In addition, there is increased melanin in the hyperkeratotic and basal layer.4,6

The diagnostic test of cleaning the affected area with alcohol also serves as a cure for the disorder; patients are treated with topical application of isopropyl alcohol, leading to a complete restoration of normal skin.1,2 This condition does not recur after treatment.6

References

  1. Borgia F, Cannavò SP. Terra firma-forme dermatosis. Clin Case Rep. 2014;2(1):19.
  2. Erkek E, Sahin S, Çetin ED, Sezer E. Terra firma-forme dermatosis. Indian J Dermatol Venereol Leprol. 2012;78(3):358-360.
  3. O’Brien TJ, Hall AP. Terra firma-forme dermatosis. Australas J Dermatol. 1997;38(3):163-164. 
  4. Browning J, Rosen T. Terra firma-forme dermatosis revisited. Dermatol Online J. 2005;11(2):15.
  5. Guarneri C, Guarneri F, Cannavò SP. Terra firma-forme dermatosis. Int J Dermatol. 2008;47(5):482-484.
  6. Pinder VAE, Eriyagama S, Saracino A, Moosa Y. Terra firma-forme dermatosis: another cause of reticulate pigmentation. Clinical Experimen Dermatol. 2012;37(4):446-447.
  7. Lora V, Ardigò M, Catricalà C, Cota C. Terra firma-forme dermatosis. J Cutaneous Pathol. 2014;41(2):141-143.