Pitted keratolysis
Introduction
A superficial
infection of the skin apparently caused by a species of Corynebacterium and
producing circular erosions on the soles.
Pitted keratolysis involves the stratum
corneum of the web spaces and plantar surface.
Etiology and
Pathogenesis
Pitted keratolysis is caused by several
bacterial species, including Corynebacterium, Dermatophilus congolensis, Kytococcus
sedentarius, actinomyces and Streptomyces, or a combination of
these organisms, that invades the stratum corneum softened by sweat and
moisture.
Pitted keratolysis occurs in adults and
children of both sexes, but adult males with sweaty feet are most susceptible
(96% of cases). Sliminess of the skin, often manifest by the foot sticking to
the socks, is also a common complaint (70% of cases). The feet are typically
very malodorous (89%) and may be mildly pruritic (8%).
Clinical
Manifestations
Pitted keratolysis presents as a superficial
erosion of the stratum corneum, composed of numerous small conspicuous, discrete, shallow, circular
pits with a punched‐out appearance coalesce in places to produce
irregular larger erosions with serpiginous borders. There is occasionally green or brown
discoloration of the horny layer. All parts of both soles may be affected,
but 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. The web spaces between the toes are also
commonly involved sites, and may be the only manifestation. Hyperhidrosis is often associated,
sometimes with maceration, stickiness and a foul odor. Soaking the feet in
water for 15 min causes swelling of the horny layer and accentuates the
lesions. Irritation is minimal and in most cases patients are unaware of the
condition. 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.
Histology
The organisms are present in the upper layer
of the stratum corneum and extending
downwards between keratinocytes. The organisms appear as coccoid
and filamentous forms with branches and septa. There is associated lysis of the keratin.
Treatment
Prophylactic
measures are aimed at keeping the feet as dry as possible. Inert antiseptic
foot powders often help.
Treatment of hyperhidrosis slowly brings the condition under control including
potassium permanganate soaks, aluminum chloride 20% solution and iontophoresis.
A benzoyl peroxide
wash and 5% gel are effective therapy in most cases as well. A more rapid response may be obtained with
fucidin ointment. Other commonly used topical adjunctive agents include clindamycin
solutions and imidazoles such as clotrimazole.
