Circumscribed palmoplanar hypokeratosis treated with complete excision

Abstract

Circumscribed palmoplantar hypokeratosis (CPH), characterized by an abrupt thinning of the corneal layer, was first reported in 2002 by Perez et al.<sup>1</sup>. It appears as a welldemarcated, round- to oval-shaped depression with an erythematous center and a slightly scaly border2. CPH develops in naturally hyperkeratotic areas such as the palms and soles<sup>2</sup>. Some studies suggest that the incidence of CPH may be underestimated, because it is often asymptomatic and can be misdiagnosed as another disease. Porokeratosis and Bowen`s disease are also included in the differential diagnosis of CPH<sup>1</sup>. To identify CPH, skin biopsy of the margin is recommended, which shows a sharp step-off of the stratum corneum<sup>2</sup>. A 62-year-old woman presented with a 6-mm solitary, well-demarcated, slightly depressed erythematous plaque with a scaly border on the radial aspect of the second metacarpal area of her left hand (Fig. 1). The lesion was first detected 3 years prior to the presentation, but was asymptomatic; hence, the patient did not visit a clinic. Moreover, she did not have any history of trauma on the area and reported no change in the size of the lesion. An excisional biopsy was performed for a definitive diagnosis and simultaneous treatment of the lesion. Histopathologic examination revealed abrupt thinning of the corneal layer at the border and a thinned stratum corneum overlying decreased granular layer on the lesional skin (Fig. 2). Cornoid lamella, parakeratosis, and other morphologic abnormalities were not seen. The clinical and histopathological findings confirmed a diagnosis of CPH. Since it was first described, CPH has been found to be a benign disorder associated with keratinization; however, its etiology remains unclear. Some studies<sup>3</sup> indicate that human papilloma virus (HPV) infection may be associated with CPH, although other studies using HPV PCR revealed that CPH was associated with HPV in only 3 cases. Immunohistochemical findings, such as abnormal cytokeratin expression, and one congenital case also support the theory that CPH is due to abnormal keratinization. A case in which actinic keratosis developed within a CPH lesion was recently reported 4; in the report, it was concluded that actinic keratosis was related to increased susceptibility to photocarcinogenesis due to thinning of the corneal layer. Other clinical characteristics of CPH include an almost solitary nature, variable size from a few millimeters to 5.5 cm (mean size, ∼1.5 cm), female predominance, age from 40 to 80 years, prolonged self-observation period, and preponderance on the right thenar eminence. CPH can be successfully treated with complete excision<sup>2</sup>. However, considering its benign nature, less invasive approaches are usually preferred. Calcipotriol ointment, photodynamic therapy, and cryotherapy are the reported successful treatment modalities for CPH<sup>2</sup>. Until recently, topical corticosteroids and retinoids have failed to show sufficient efficacy<sup>2</sup>. In Korean dermatologic journals, 4 cases of CPH have been reported<sup>5</sup>. In one case, only skin biopsy was performed; in two cases, calcipotriol ointment was unsuccessfully used; and in one case, CPH was successfully treated with cryotherapy<sup>5</sup>. In case of appropriate size and anatomical location like our case, complete excision can be a proper option for simultaneous diagnosis and treatment.