The FP diagnosed pitted keratolysis in this patient. Pitted keratolysis is a superficial foot infection caused by Gram-positive bacteria, including Kytococcus sedentarius, Corynebacterium species, and Dermatophilus congolensis.
These bacteria produce proteases that degrade the keratin of the stratum corneum, leaving visible pits on the soles of the feet. The condition is typically seen in people with chronically wet feet, such as rice paddy workers. The associated malodor in some patients is likely secondary to the production of sulfur byproducts; in this case, however, the wide-open plastic shoes that the patient wore did not retain any odor.
Pitted keratolysis may be associated with an itching and burning sensation in some patients. Pitted keratolysis usually involves the callused pressure-bearing areas of the foot, such as the heel, ball of the foot, or plantar great toe. It can also be found in friction areas between the toes, as seen in this patient.
Treatment is based on eliminating bacteria and reducing the moist environment in which the bacteria thrive. Topical erythromycin or clindamycin solution can be applied twice daily until the condition resolves. It may take 3 to 4 weeks to clear the skin lesions. Oral erythromycin is effective and may be considered if topical therapy fails.
In this case, the FP prescribed oral erythromycin because that was the only option available. He also encouraged the boy to keep his feet as dry as possible, despite the rainy climate and the fact that he didn’t have access to socks.
Photo and text for Photo Rounds Friday courtesy of Richard P. Usatine, MD. This case was adapted from: Babcock M, Usatine R. Pitted keratolysis. In: Usatine R, Smith M, Mayeaux EJ, et al, eds. Color Atlas of Family Medicine. 2nd ed. New York, NY: McGraw-Hill; 2013:686-688.
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