Features of Terra Firma-Forme Dermatosis

DISCUSSION

TFFD is a keratinization disorder with an asymptomatic dirt-like appearance that occurs despite adequate hygiene. It should be differentiated from dermatosis neglecta, acanthosis nigricans, neurodermatitis, ichthyosis, pityriasis versicolor, epidermal nevi, and confluent and reticulated papillomatosis.^1–12 The lesions can be mistaken for dirt, even though the patient’s hygiene is good. The dirt-like lesions make patients and their parents uncomfortable; they report, “We are constantly washing these places with soap.” In addition to the parents’ observation, when examining the patient, the physician can differentiate the lesions from dermatosis neglecta and real dirt.

Aggressive diagnostic and therapeutic approaches can result when the physician does not recognize TFFD. For example, a skin biopsy was taken from a girl with a presumed diagnosis of ichthyosis vulgaris (Supplemental Figure 1). Before arrival at our clinic, another patient was believed to have pityriasis versicolor, and treatment was attempted using antifungal medication.

The exact cause of TFFD is still unclear. Histopathological studies are limited, but lamellar hyperkeratosis, compact orthokeratosis with whorls, keratin globules in the stratum corneum, increased melanin, and Malassezia furfur spores in the basal layer have been reported.^2–6 The clinical appearance of TFFD may be explained by an abnormal keratinization and accumulation of melanin and dirt within the epidermis. Further histopathologic studies, however, may be useful in terms of illuminating the etiopathogenesis of the disease.

Genetic predisposition has been mentioned in previous case reports.^1–12 In our study group, 2 patients were siblings and had xerosis. This finding suggests a genetic predisposition, but wider studies are needed to address this possibility.

Emollients and sun exposure have also been reported as causative factors.^3,4 Because our patients reported no history of regular emollient use, even those with atopic dermatitis and keratosis, we believe that emollient usage is not a causative factor. There may be a relationship between TFFD and xerosis, which is also a disorder of keratinization. Our patients had lesions in places that were not exposed to the sun, which would suggest there is no relationship between sun exposure and TFFD.

Some patients had acne, seborrheic dermatitis, rosacea, and vitiligo, but the locations of the TFFD lesions were different from where these lesions were found. According to our results, there may be no relationship between these dermatoses and TFFD. Further studies about accompanying skin diseases may be informative about the etiopathogenesis of TFFD.

A total of 18 patients had other systemic diseases, such as allergic rhinitis, allergic asthma, urinary tract infection, hypothyroidism, osteosarcoma, and chronic myeloid leukemia. There is no report describing the relation of these diseases with TFFD. Future studies may be useful to determine whether other systemic diseases are related TFFD.

In previous case reports, lesions were found to be mostly on skin folds.^1–12 In our study, more than 1 anatomical region was involved. Lesions were found on the trunk, extremities, skin folds (neck, axilla, inguinal region, umbilical fold), and face in decreasing order.

TFFD has been reported to affect both sexes equally and affect all age-groups, though mostly children.^1–12 In our study, most of our patients were children and female. Women take more care about their appearance and are more likely to notice these lesions on themselves. Even so, most of our patients were children, and the lesions had been noticed by the parents. The predominance of female patients therefore cannot be related to a tendency of women to notice TFFD lesions. Studies about predominance of TFFD in female patients may be useful in further understanding the etiopathogenesis of this disease.

In previous cases reports, recurrence was not reported.^1–12 Our findings were similar; during a period of 19 months, no recurrence was seen. Even so, 5 patients reported a history of recurrence, and we believe there may have been more recurrences than we evaluated. When lesions reappeared, patients may have cleaned them with isopropyl alcohol and chose not return to our clinic.

TFFD is predominantly a childhood dermatosis, mostly seen in female patients, and it may be more common than expected. Wiping the lesions with alcohol is both diagnostic and therapeutic. TFFD should be kept in mind in the differential diagnosis of hyper-pigmented and hyperkeratotic lesions to avoid unnecessary diagnostic testing and therapeutic treatments.