Terra firma-forme dermatosis revisited
Baylor College of Medicine and Michael E. DeBakey Veterans Affairs Medical Center, Houston, Texas. firstname.lastname@example.org
Terra firma-forme dermatosis is a cutaneous discoloration resembling dirt, hence the clinical name. The dyschromia cannot be removed with routine soap and water washing, but can be eliminated by rubbing with isopropyl alcohol. Although the condition poses no serious medical threat, it is cosmetically distressing. Our experience is that this entity is much more frequent that might be expected when considering the paucity of reports in the readily available medical literature. We chronicle a series of cases to highlight occurrence in widely divergent demographic groups and long duration of remission following appropriate topical intervention. The cause remains unknown.
Terra firma-forme dermatosis is a relatively recently described entity which, in our experience, is much more common than might be expected when surveying the medical literature [1, 2, 3, 4]. Although it poses no serious medical threat, it is quite cosmetically distressing. Clinical recognition leads to prompt and simple therapy, thereby avoiding complex and costly evaluation. We herein document and illustrate six cases of this bizarre dermatosis whose etiology remains uncertain.
A 54-year-old healthy white male presented with a many-year history of an asymptomatic brown rash on the trunk. The patient assured the examiners that he maintained good hygiene, including daily showers with soap. Physical exam disclosed palpable, papillomatous brown plaques on his back as well as his neck and periaxillary skin (Fig. 1). Areas of dark-brown hyperpigmentation could be completely rubbed off with isopropyl alcohol (Fig. 2). A 3.5-mm punch biopsy from an affected area revealed prominent lamellar hyperkeratosis with focal areas having compact orthokeratosis arranged in whorls (Figs. 3 and 4). Vigorous alcohol rubbing removed virtually all of the pigmentation. The patient was lost to long-term followup.
A 19-year-old white female college student complained of gradually increasing, asymptomatic discoloration involving the neck and both arms. The patient was a fastidious individual, showering once or twice daily. She was healthy and ingesting neither medications nor nutritional supplements. Physical examination disclosed subtle but clear-cut light-brown hyperpigmentation involving both sides of the neck and the lateral aspect of both upper arms (Fig. 5). The patient refused biopsy when it became obvious that all areas could be easily cleared by rubbing with isopropyl alcohol (Fig. 6). The patient remained free of dyschromia 2 years following removal of all abnormal pigmentation with alcohol.
A 72-year-old relatively healthy white male presented with a 1-year history of multiple asymptomatic scalp lesions. The patient routinely cleansed his scalp with over-the-counter shampoo at least three times weekly. Physical examination disclosed eight prominent, irregularly-shaped jet-black plaques scattered on the central and posterior scalp (Fig. 7). The neck, torso, and arms were uninvolved. Differential diagnosis comprised primarily of tumors: pigmented basal cell carcinoma, squamous cell carcinoma in situ, seborrheic keratosis, and melanocytic neoplasia. However, several of the areas were easily and completely removed by light rubbing with isopropyl alcohol, confirming the diagnosis of dirty dermatosis of the scalpv (Fig. 8). All lesions were then removed in a similar manner, and the patient remains clear 3 years later.
A 9-year-old boy of Indian ancestry was brought by his mother for a second opinion. She had been told that her son had acanthosis nigricans due to the velvety-textured, dark hyperpigmentation present on both sides of his neck for the past 6 months (Fig. 9)/ She was further advised that no treatment was available. Extensive and expensive laboratory evaluation detected no endocrine abnormalities. The area was easily normalized by lightly rubbing with isopropyl alcohol (Fig. 10). The child remained free of pigmentation 6 months following rigorous cleansing of all affected areas with alcohol.
A 27-year-old white female homemaker complained of a patch of discoloration on the front of the neck which could not removed by soap and water (Fig. 11). She showered daily, had no chronic illnesses and was ingesting no medication. The small area cleared easily when swabbed with isopropyl alcohol. She remains free of this annoyance over 26 years later.
A healthy 30 year-old white male sought dermatological consultation regarding discoloration of the arms while hospitalized for open fracture reductions following automotive trauma. He worked in an office environment, showered once or twice daily, and was taking no medications. Physical examination disclosed dark-brown patches involving the middle third of the dorsal aspect of both arms (Fig. 12). All areas were restored to normal by rubbing with isopropyl alcohol (Fig. 13). Phone follow up 1 year later revealed that the lesions had not returned.
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 . 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 . 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  and the pubic region . 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 .
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 event of recurrence, once a week application of isopropyl alcohol will suffice as prophylaxis.
Awareness of terra firma-forme dermatosis facilitates prompt diagnosis and thereby prevents unnecessary biopsy and extensive endocrine evaluation. As illustrated by our case series, this condition can affect both sexes, as well as youthful to geriatric individuals. While the neck is a common site, terra firma-forme dermatosis can also appear on other body regions, from the extremities and torso to the scalp. It is very satisfying for both the patient and clinician to see a cosmetically bothersome skin condition disappear with simple application of isopropyl alcohol. Patients feel reassured knowing that they do not have a serious illness or a permanently disfiguring condition.
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