Pitted keratolysis is caused by pedal hyperhidrosis and subsequent overgrowth of bacteria that produce proteinases that dissolve keratin and lead to pit formation.
A 33-year-old man presented for medical attention because of the presence of “a bad smell” on the feet. The patient was healthy, took no medications, and regularly engaged in sports activities. Examination of the feet revealed non-tender, superficial pits in the skin of the toes and the heel.
Key point: This is the typical appearance of pitted keratolysis. This disorder is caused by pedal hyperhidrosis and subsequent overgrowth of one or more causative species of bacteria (Kytococcus sedentarius; Dermatophilus congolensis; and species of Streptomyces, Actinomyces, and Corynebacterium). The bacteria produce proteinases that dissolve keratin and lead to formation of pits.
Treatment: The patient was instructed to change socks frequently, wash his feet after each sporting event, apply an aluminum-containing antiperspirant to the soles 1 or 2 times weekly, and apply mupirocin 2% ointment twice daily.
Note: The malodor that accompanies this disease is caused by release of sulfur-containing compounds as keratin is being digested by bacterial enzymes.