Terra Firma Forme

Terra firma-forme dermatosis has likely afflicted mankind throughout the ages but was only first described in the medical literature in the twentieth century. It derives its name from the Latin phrase terra-firma meaning dry land (dirt), thus implying dirt-like dermatosis. However, it has also been referred to as Duncan's Dirty Dermatosis in honor of the physician who initially described this condition in Houston in 1987 [1]. Terra firma-forme dermatosis is characterized by brown, dirt-like discoloration that cannot be removed by bathing with water or rubbed off with routine detergent soap. It It has most often been seen in children [1, 2 ,3 ,4] but it has also been described in adults [1]. When involving children, it can be very distressing to their parents who cannot obtain clean appearing skin with routine cleansers. Terra firma-forme dermatosis most often involves the neck and trunk but has also been reported on the scalp [3] and the pubic region [4]. Our case series graphically demonstrates the wide range of ages (ages 9-72) and sites (neck, arm, back, axillary line, and scalp) that can be affected.

The cause of terra firma-forme dermatosis is unknown. At fist glance these patients may appear to have confluent and reticulated papillomatosis (CARP) or acanthosis nigricans. However, when biopsy is performed to clarify the diagnosis, the dirty dermatosis often wipes off with the alcohol pad being used to prep the skin. In many cases, aggressive effort with application of substantial shearing force is required to remove the brown pigmentation. Therefore, when this condition is suspected, firm, persistent pressure should be applied while rubbing the skin with alcohol.

Histopathologic examination of terra firma-forme dermatosis reveals prominent lamellar hyperkeratosis with focal areas having compact orthokeratosis in whorls; no parakeratosis is seen. Duncan, Tschen, and Knox also performed additional histopathologic studies in their initial report; Fontana-Masson-stained sections showed increased melanin in the compact hyperkeratotic areas and the basal layer. Toluidine blue staining of plastic-embedded sections showed numerous keratin globules throughout the thick stratum corneum. Periodic acid-Schiff stains demonstrated occasional yeast cells thought to be Pityrosporrum. Brown-Bren-stained tissue sections showed only normally distributed bacteria [1].

For patients with extensive terra firma-forme dermatosis, educating the patient or their accompanying family member on how to clean their skin at home using isopropyl alcohol will save an extensive amount of time from performing the same service in the clinic. In our experience, recrudescence is exceptionally rare, even though individuals do not alter their cutaneous habits or exogenous exposures in any way. In this case series, one patient had over 25 years of clearance and the others remained clear from 6 months to 3 years. In the uncommon

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