Terra firma-forme dermatosis

Terra firma-forme dermatosis (TFFD) is a benign condition presenting with brown-black, dirt-like areas of affected skin. 

This chapter is set out as follows:

• TFFD is thought to be a disorder of keratinisation - prolonged adhesion between keratinocytes leads to the formation of the brown-black patches seen in this condition

• TFFD is asymptomatic, mainly affecting children and adolescents, although any age group can be affected
• There is no predilection for any particular gender and TFFD is unrelated to any known genetic condition or familial inheritance
• There is a suggestion that it presents more commonly in the warmer months 
• Poor hygiene is not related and the affected skin may be resistant to scrubbing with soap and water

Distribution

• TFFD can be localised, generalised, bilateral, or unilateral
• The neck and other flexural sites, along with the face, trunk, and ankles, are the most commonly affected areas, although any area of the body can be affected
• TFFD has been reported around surgical sites
  
• Rarely, it can be more extensive

Morphology

• Brown-black macules, papules, or plaques resembling dirty skin 
• Lesion may may also have a papillomatous, verrucous, or reticulate appearance

• The diagnosis is clinical and can be confirmed by removing the affected skin using alcohol wipes 

• Referral is not needed
• Once removed lesions rarely recur, but if they do they may be amenable at any early stage to washing off using a soapy flannel, or failing that they can be washed off with a preparation containing 70% isopropyl alcohol