Linear dermatoses over the hand and foot

A 20-year-old male student presented to the dermatology outpatient department with a history of thickening over the right palm and left foot since childhood. The lesions were asymptomatic. There was no history of similar lesions among the family members. On examination, linear hyperkeratosis was noted along the lateral margin of the right palm extending from the thenar eminence to the thumb tip. Similar linear hyperkeratosis was noted over the dorsum of the foot [Figures 1 and 2]. On investigation, all hematological and biochemical parameters were normal. Histopathology from the palm revealed massive hyperkeratosis with acanthosis of the epidermis [Figure 3]. Topical keratolytics provided only marginal improvement.

Figure 1.

Linear hyperkeratosis along the lateral margin of the right palm extending from the thenar eminence the thumb tip

Figure 2.

Linear hyperkeratosis over the left foot

Figure 3.

Histopathology revealed massive hyperkeratosis with acanthosis of the epidermis. (H and E, ×40)

ANSWER

Striate palmoplantar keratoderma (Brunauer-Fuhs-Siemens type).

DISCUSSION

Hereditary palmoplantar keratodermas (PPK) are a heterogeneous group of diseases characterized by hyperkeratosis of the palms and soles with thickening of the stratum corneum, usually distinguishable by the mode of inheritance and associated clinical findings.[1,2]

Clinically, three distinct patterns of palmoplantar keratodermas are seen, as follows:[1]

1. Diffuse palmoplantar keratodermas, characterized by even, thick, and symmetrical hyperkeratosis over the palms or soles

2. Focal palmoplantar keratodermas, in which a large, compact mass of keratin develops at the site of recent friction

3. Punctuate palmoplantar keratodermas, in which multiple, tiny “rain drop” keratoses involve the palmoplantar surface.

Striate palmoplantar keratoderma (Brunauer-Fuhs-Siemens type) is a rare variant of focal PPK characterized clinically by linear and focal hyperkeratosis of the palms and soles.[1] Linear involvement of the dorsum of the foot has not been described.

The condition is of autosomal dominant inheritance. Genetically, the disease is heterogeneous as linkage has been found to two separate loci: To desmogleins (DSG1-3) and the desmocollins (DSC1-3) at chromosome 18q12 and to desmosomal plaque protein and desmoplakin at chromosome 6p21.[3] Thus, striate palmoplantar keratoderma is a genetically heterogeneous disorder of keratinization, which may account for the variable clinical manifestations.[4]

Onset of the disease is in infancy or during the first few years of life. Involvement of the sole is mainly seen, followed by that of palms. In our patient there was involvement of the dorsum of the foot in addition to the lesions over the palm, which has not been reported. The elbows and knees may also be involved. Skin fragility, nail, and hair involvement may be rarely seen.[1] Keratolytics are the mainstay of therapy. Use of topical and oral retinoids has also been described.[4]