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A teenage boy with smelly feet
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A 14-year-old boy presents to your office for his yearly checkup. He has no specific concerns; however, his mother complains that his feet smell terrible. She has noticed the odor for several months, despite appropriate hygiene and the purchase of new shoes. You examine the plantar surface of both feet and find several scattered 1-mm to 15-mm skin-colored and erythematous pits and superficial erosions, which are limited mainly to the weight-bearing surfaces of the soles and lateral aspects of several toes. The patient and his mother were completely unaware of these skin findings and cannot tell you how long they have been present.
What is the most likely etiologic agent?
Pitted keratolysis (PK) is a common, asymptomatic bacterial infection of the skin most commonly involving the weight-bearing surfaces of the feet and occasionally the palms. Many patients are completely unaware of the eruption unless they notice the malodor or, occasionally, the lesions become tender. Topical antibiotics are the preferred treatment.
Clinically, the characteristic lesions appear most commonly as 1 mm to 7 mm crateriform or circular pits often involving the plantar furrows. The pits coalesce to form one to several centimeter shallow erosions on the plantar aspects of the toes, ball of the foot and heel, but they can occur anywhere on the foot, as well as on the palms. Areas prone to friction such as the interface region of the toes may also be affected. The eruption is most common in warm tropical climates, especially among people who walk barefoot, but can be seen in any population. Predisposing features include hyperhidrosis and a warm, wet environment. Malodor is common and may be the presenting complaint. Patients may also complain of a wet, sticky or slime-like material on the surface of the soles.
Corynebacterium minutissimum and Micrococcus sedentarius are commonly implicated in PK and can be seen on histopathologic examination. On microscopic examination with hematoxylin-eosin staining, numerous microorganisms can be found in the walls and bases of the crateriform depressions in the stratum corneum. Gomori methenamine silver and periodic acid-Schiff further highlight the organisms.
The diagnosis is usually made clinically based on the findings of pits, erosions and malodor. Other common foot dermatoses that may be confused with PK include tinea pedis and plantar warts (verruca plantaris). Tinea pedis usually involves weight-bearing and nonweight-bearing aspects of the feet, as well as the lateral edges of the feet and interdigital web spaces of the toes. Although plantar warts have a similar distribution to PK, they are usually well-defined, often painful, skin-colored hyperkeratotic papules without associated erosion or malodor.
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Figure 1: The plantar surface of both feet
have several scattered 1-mm to 15-mm skin-colored and erythematous pits and
superficial erosions. Photos courtesy of Anne W. Lucky, MD |
PK may resolve without treatment but often shows a relapsing and remitting course. Preventive measures such as wearing proper fitting shoes with cotton socks or open sandals or flip-flops to provide a dry environment may lead to resolution. In addition, measures to decrease perspiration, such as 20% topical aluminum chloride preparations (Drysol, Mora Health) may help. First-line treatment includes topical antibiotics such as erythromycin 2% solution, clindamycin 1% solution or mupirocin ointment. The eruption should resolve within 3 to 4 weeks after initiation of treatment.
PK is a common foot dermatosis that often goes unnoticed by the patient until malodor or discomfort develops. It is important to have patients remove their socks and shoes upon physical examination, as many physicians may diagnose PK upon routine physical examination and help to limit the severity of the disease.
For more information:
- Blaise G. Int J Dermatol. 2008;47:884-890.
- Ramsey ML. Phys Sportsmed. 1996;24:51-56.
- Takama H. Br J Dermatol. 1997;137:282-285.
Marissa J. Perman, MD, is a third-year dermatology resident at the University of Cincinnati.
Disclosure: Dr. Perman reports no relevant financial disclosures.