A 17-year-old boy comes to the office with a terrible foot odor problem. He is wearing cowboy boots and he says that his feet are always sweaty. He is embarrassed to remove his boots, but when his mother convinces him to do so the odor is unpleasant. The clinician sees the typical pits of pitted keratolysis and notes that the boy’s socks are moist. His foot has many crateriform pits on the sole (Figure 101-1). He is prescribed topical erythromycin solution for the pitted keratolysis and topical aluminum chloride for the hyperhidrosis. It is suggested that he wear a lighter and more breathable shoe until this problem improves.
Many crateriform pits on the heel of the foot with pitted keratolysis and hyperhidrosis. (Used with permission from Richard P. Usatine, MD.)
Pitted keratolysis is a superficial foot infection caused by Gram-positive bacteria. These bacteria degrade the keratin of the stratum corneum leaving visible pits on the soles of the feet.
Seen more commonly in males.
Often a complication of hyperhidrosis.
Seen more often in hot and humid climates.
Prevalence can be as high as 42.5 percent among paddy field workers.1
May be common in athletes with moist, sweaty feet.2
Etiology and Pathophysiology
Kytococcus sedentarius (formerly Micrococcus spp.), Corynebacterium species, and Dermatophilus congolensis have all been shown to cause pitted keratolysis.3
Proteases produced by the bacteria degrade keratins to give the clinical appearance.4
The associated malodor is likely secondary to the production of sulfur byproducts.3
Pitted keratolysis usually presents as painless, malodorous, crateriform pits coalescing into larger superficial erosions of the stratum corneum (Figures 101-1 to 101-4). It may be associated with itching and a burning sensation in some patients (Figure 101-3).
Pitted keratolysis on the pressure-bearing areas of the toes and the ball of the foot. (Used with permission from Richard P. Usatine, MD.)
Pitted keratolysis with hyperpigmented crateriform pits on the pressure-bearing areas of the foot. The patient complained of itching and burning on the feet. (Used with permission from Richard P. Usatine, MD.)
Pitted keratolysis with many crateriform pits on the heel. (Used with permission from Richard P. Usatine, MD.)
Pitted keratolysis usually involves the callused pressure-bearing areas ...