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Terra firma-forme dermatosis

Author: Dr Lachlan Andrew Byth, Resident Medical Officer, Ipswich Hospital, Ipswich, QLD, Australia; and Associate Lecturer, Griffith University, Southport, QLD, Australia. DermNet NZ Editor in Chief: Adjunct A/Prof. Amanda Oakley, Dermatologist, Hamilton, New Zealand. Copy edited by Gus Mitchell. October 2019.


What is terra firma-forme dermatosis?

Terra firma-forme dermatosis is a benign skin disorder that manifests as raised, dirty-appearing areas of skin. It is also called Duncan’s dirty dermatosis in honour of the dermatologist who first described it [1].

Terra firma is Latin for ‘dry land,’ reflecting the appearance of affected areas as islands of dirty skin. These areas are not truly dirty but give this impression due to abnormal keratinisation.

Who gets terra firma-forme dermatosis?

Terra firma-forme dermatosis mainly affects children and adolescents [2]. However, there have not been any large epidemiological studies to determine how prevalent it is. It may be more common given that it is asymptomatic, and many people are not likely to seek medical attention for it.

What causes terra firma-forme dermatosis?

Terra firma-forme dermatosis is thought to be a disorder of keratinisation caused by abnormal and delayed development of skin cells. Adhesion between keratinocytes is prolonged, causing them to accumulate as brown patches and thickened plaques [3].

It has previously been attributed to poor personal hygiene. However, affected areas are actually resistant to washing with normal soap, and many patients have normal standards of cleanliness.

It is possible that terra firma-forme dermatosis is a ‘forme fruste’ (an atypical manifestation of another condition) of confluent and reticulated papillomatosis of Gougerot and Carteaud [4].

What are the clinical features of terra firma-forme dermatosis?

Terra firma-forme presents with thickened, brown-black papules and plaques on the neck, trunk, face, and abdomen. The patient has normal washing habits.

Terra firma-forme has been reported around surgical sites, such as after total knee replacement or median sternotomy [5]. Rarely, it can present with extensive areas of involvement over the chest, abdomen, and thighs [6].

What are the complications of terra firma-forme dermatosis?

Psychosocial distress can result from the dirty appearance which may be perceived to reflect poor personal hygiene.

How is terra firma-forme dermatosis diagnosed?

Terra firma-forme dermatosis is a clinical diagnosis that should be suspected in children and adolescents with dirty-appearing areas, particularly on the neck, which cannot be removed with soap.

  • Wiping affected areas with a pad soaked in 70% isopropyl alcohol will completely remove the lesions and is simultaneously diagnostic and therapeutic [7].
  • Large brown polygonal areas in a mosaic-like pattern are seen on dermoscopy.
  • Further testing is typically not necessary, but laboratory tests for fungal infection may sometimes be performed to rule out pityriasis versicolor.
  • A skin biopsy is rarely performed. The findings are mostly nonspecific and include papillomatosis, acanthosis, and orthohyperkeratosis. Keratin whorls are sometimes seen and may be specific for the diagnosis [4].

What is the differential diagnosis for terra firma-forme dermatosis?

There are several other ‘dirty dermatoses’ which mimic terra firma-forme dermatosis, including:

  • Dermatitis neglecta, which results from inadequate cleansing of the skin and responds to washing with normal soap and water [8]
  • Acanthosis nigricans, which causes velvety lesions distributed symmetrically in intertriginous areas and is associated with obesity, metabolic syndrome and, occasionally, internal malignancy [9]
  • Confluent and reticulated papillomatosis of Gougerot and Carteaud, which presents with brown papules which coalesce into plaques, distinguished by their reticular or net-like periphery and confluent centre, as well as their resistance to even vigorous rubbing with alcohol [10]
  • Dirty neck syndrome, which refers to dirty-appearing acquired hyperpigmentation of the anterior and lateral neck seen in patients with atopic dermatitis, particularly in Asian populations [11]
  • Symmetrical acrokeratoderma, which presents with dirt-like hyperkeratotic areas distributed symmetrically on the upper and lower limbs, particularly the wrists, ankles, and dorsa of the hands and feet [12]
  • Seborrhoeic keratosis, which is a benign growth of keratinocytes. Multiple superficial seborrhoeic keratoses may appear similar to terra firma-forme dermatosis, but do not clear up after rubbing with alcohol.

Other conditions to consider include:

What is the treatment for terra firma-forme dermatosis?

Rubbing with ethyl or isopropyl alcohol-soaked wipes completely removes the dirty-appearing areas.

Mild topical keratolytic agents (eg, 5% salicylic acid in petrolatum ointment) can be used in extensive cases to avoid aggressive rubbing of large areas [13].

Chemical peels (eg, 20% salicylic acid in alcohol) are reported to lead to rapid resolution of the condition [14].

What is the outcome for terra firma-forme dermatosis?

Terra firma-forme dermatosis usually responds completely to treatment. Patients can be reassured that this is a benign condition, and that they can use alcohol wipes to remove any recurrent lesions.

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References

  1. Duncan WC, Tschen JA, Knox JM. Terra firma-forme dermatosis. Arch Dermatol 1987; 123: 567–9. PubMed
  2. Berk DR. Terra firma-forme dermatosis: a retrospective review of 31 patients. Pediatr Dermatol 2012; 29: 297–300. PubMed
  3. Errichetti E, Stinco G. Dermoscopy in terra firma-forme dermatosis and dermatosis neglecta. Int J Dermatol 2017; 56: 1481–3. PubMed
  4. Berk DR, Mutizwa MM. Comment regarding the histopathology of terra firma-forme dermatosis. J Cutan Pathol 2012; 39: 300–1; author reply 2-3. PubMed
  5. Ashique KT, Kaliyadan F, Goyal T. Terra firma-forme dermatosis: report of a series of 11 cases and a brief review of the literature. Int J Dermatol 2016; 55: 769–74. PubMed
  6. Panchal K, Bhalla N, Salunke P, Jerajani H. Extensive terra firma forme dermatosis [TFFD]: A rare presentation. Indian Dermatol Online J 2015; 6: 458–9. PubMed Central
  7. Blattner CM, Perry B, Snider K, Young J, 3rd. Clinical pearl: increasing utility of isopropyl alcohol for cutaneous dyschromia. Cutis 2016; 97: 287; 301. PubMed
  8. Poskitt L, Wayte J, Wojnarowska F, Wilkinson JD. 'Dermatitis neglecta': unwashed dermatosis. Br J Dermatol 1995; 132: 827–9. PubMed
  9. Kutlubay Z, Engin B, Bairamov O, Tuzun Y. Acanthosis nigricans: a fold (intertriginous) dermatosis. Clin Dermatol 2015; 33: 466–70. PubMed
  10. Scheinfeld N. Confluent and reticulated papillomatosis : a review of the literature. Am J Clin Dermatol 2006; 7: 305–13. PubMed
  11. Seghers AC, Lee JS, Tan CS, Koh YP, Ho MS, Lim YL, et al. Atopic dirty neck or acquired atopic hyperpigmentation? An epidemiological and clinical study from the National Skin Centre in Singapore. Dermatology 2014; 229: 174–82. PubMed
  12. Liu Z, Zhou Y, Chen RY, Shi G, Li W, Li SJ, et al. Symmetrical acrokeratoderma: A peculiar entity in China? Clinicopathologic and immunopathologic study of 34 new cases. J Am Acad Dermatol 2014; 70: 533–8. PubMed
  13. Vakirlis E, Theodosiou G, Lallas A, Apalla Z, Sotiriou E. Terra firma-forme dermatosis: Differential diagnosis and response to salicylic acid therapy. Pediatr Dermatol 2019; 36: 501–4. PubMed
  14. 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: 83–5. PubMed

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