A 34-year-old man 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 the physician convinces him to do so the odor is overwhelming. While breathing through the mouth, the physician sees the typical pits of pitted keratolysis. His socks are moist and the skin is somewhat macerated from the hyperhidrosis. His foot has many crateriform pits on the heel (Figure 124-1). 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 a foot in a man with pitted keratolysis and hyperhidrosis. (Reproduced 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 men.
Often a complication of hyperhidrosis.
Seen more often in hot and humid climates.
Prevalence can be as high as 42.5% 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 by-products.3
Pitted keratolysis usually presents as painless, malodorous, crateriform pits coalescing into larger superficial erosions of the stratum corneum (Figures 124-1, 124-2, 124-3, 124-4). It may be associated with itching and a burning sensation in some patients (Figure 124-3).
Pitted keratolysis on the pressure-bearing areas of the toes and the ball of the foot. (Reproduced 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. (Reproduced with permission from Richard P. Usatine, MD.)
Pitted keratolysis with many crateriform pits on the heel. (Reproduced with permission from Richard P. Usatine, MD.)