Pitted Keratolysis
Pitted keratolysis involves the stratum corneum of the web spaces and plantar surface. Originally named keratoma plantare sulcatum by Castellani in 1910, this disease has become more commonly called by its current name after Taplin and Zaias coined it in 1967. The disease was first seen in those who went barefooted during the rainy season.
ETIOLOGY AND PATHOGENESIS
The likely causative organism is Micrococcus sedentarius, which is a Gram-positive staphylococcus-related bacterium that invades the stratum corneum softened by sweat and moisture. Corynebacterium sp. may also be involved. Pitted keratolysis tends to be much more severe in tropical climates than in temperate ones.
Pitted keratolysis occurs in adults and children of both sexes, but adult males with sweaty feet are most susceptible (96 percent of cases). Sliminess of the skin, often manifest by the foot sticking to the socks, is also a common complaint (70 percent of cases). The feet are typically very malodorous (89 percent) and may be mildly pruritic (8 percent).
CLINICAL MANIFESTATIONS
Pitted keratolysis presents as a superficial erosion of the stratum corneum, composed of numerous small crateriform pits coalescing to form a large discrete defect with serpiginous borders on the plantar surface of the foot. The pits are usually larger than 0.7 mm in diameter, but at times are smaller than 0.5 mm. The pits have elongated configurations along the plantar furrows and are located predominantly on the pressure-bearing areas, such as the ventral aspect of the toe, ball of the foot, and the heel, but they are also seen on non-pressure-bearing areas.31 The web spaces between the toes are also commonly involved sites, and may be the only manifestation . The diagnosis is made clinically.
DIFFERENTIAL DIAGNOSIS
Interdigital tinea pedis can present with erosive lesions in the web spaces. Erythrasma in the web spaces is usually hyperkeratotic but can be erosive.
LABORATORY FINDINGS
Gram-staining of scrapings may detect the microorganism more readily than potassium hydroxide examination. Histologically, the organisms are present in the walls and bases of the crateriform defects in the upper layer of the stratum corneum. The organisms appear as coccoid and filamentous forms with branches and septa.
TREATMENT
Prophylactic measures are aimed at keeping the feet as dry as possible. Inert antiseptic foot powders often help. Aluminum chloride 20 percent solution is an effective astringent. A benzoyl peroxide wash and 5 percent gel are effective therapy in most cases as well. Other commonly used topical adjunctive agents include clindamycin and erythromycin solutions.
