Terra firma-forme in 64-year-old Black patient.
This article describes the case of a 64-year-old Black male patient who presented to the emergency with a 1-year history of an asymptomatic rash. The patient’s medical history revealed hypertension, diabetes and obesity. He had no complaints of any other skin conditions nor had he experienced a similar rash before. The rash was first noticed by his wife. He used an antifungal cream to first clear up the rash, however, it did not help. He also tried scrubbing the lesions with soap and water while taking a shower everyday, although with no improvement. Doctors diagnosed the slowly progressing rash as terra firma–forme dermatosis, based on the clinical findings and investigations.
Terra firma-forme can be diagnosed in the clinic. The plaques disappear when rubbed with 70% isopropyl alcohol and ethyl alcohol. In several cases, aggressive rubbing can help remove the hyperpigmentation completely. The skin condition was first described in 1987 and is also referred to as Duncan dirty dermatosis because the hyperpigmented plaques look like dirt on the skin. Terra firma-forme dermatosis can affect patients of any age, however, more frequently affects children and adolescents. There is no gender predilection and it is not related to familial inheritance or a specific gene.
The lesions are usually black or brown and can be verrucous, reticular or papillomatous.
The plaques can be visible anywhere on the body but are more commonly seen on the trunk and the neck. Other areas where the lesions may appear include the ankles, face, legs, back, axillary, pubic and umbilical regions. In addition, the rash can localised or generalised and is more commonly found on the skin folds and concave skin areas. Although the cause of the skin condition is unknown, a theory is that it may be caused because of slowed keratinocyte maturation, dirt and sebum build up, melanin retention and keratin squames. Potential predisposing factors include sun exposure and use of emolients that contain urea.
It has also been associated with atopic dermatitis and xerosis. Similarly, it can even affect patients with good hygiene. Treatment for terra firma-forme includes rubbing with 70% isopropyl alcohol or ethyl alochol. In this case, the patient’s plaque was treated in the clinic with 70% isopropyl alcohol. And he continued the treatment at home which led to a complete resolution of the lesions on his back. On follow-up, the lesions had not recurred.
Hyperpigmented Plaques on Trunk https://www.clinicaladvisor.com/home/dermatologic-look-alikes/hyperpigmented-plaque-on-trunk/2/