When A Patient Presents With Malodorous, Macerated Feet

By M. Joel Morse, DPM

Key Questions To Consider

   1. What essential question does one still need to help make the diagnosis?
   2. What is the tentative diagnosis?
   3. Can you list at least three differential diagnoses?
   4. What features in this condition differentiate it from other conditions?
   5. What is the suitable treatment of this condition?

   A 27-year-old Caucasian male presents with a history of a strong smell of the feet for the past five years. He is very active in sports. The patient says he has to replace his shoes every three months and that his family and friends are always aware of the smell.

   The patient notes that his feet are becoming a nuisance. He also says his hands and feet sweat a lot. The patient has been aware of scaling on his feet for five years but denies any pain related to the feet. He also denies any pruritus. The patient denies any systemic history at this time. He notes that the pits are more noticeable after he swims or gets out of the shower.

   The patient has not seen any health care providers for the condition but has used OTC powders and antifungal medications with no lasting result.

   During the clinical examination, I noted symmetric plantar lesions/pits on both feet, including the heels, metatarsal areas and the plantar aspect of the hallux. Many small craterform crypts on the heels coalesced to form larger erosions on both feet.

   The pits appear to be between 2 mm to 3 mm in size. The lesions had a white-yellowish appearance and an unpleasant odor. There was some involvement of the posterior aspect of the heel as well as the ball of the foot. The arches and sides of the feet were spared.

   I did not note any scales, erythema or tenderness. There was no toenail involvement. A potassium hydroxide (KOH) test of the lesion was negative for hyphae but an aerobic bacterial swab was positive for Corynebacterium species. A Wood’s lamp examination was also negative.

Answering The Key Diagnostic Questions

   1. Does the patient’s skin feel slimy or do his socks stick to his skin?
   2. Pitted keratolysis
   3. Hyperhidrosis, erythrasma and superficial candidiasis
   4. Discrete shallow circular lesions with a punched out appearance
   5. Keeping feet dry and using topical antibacterials

What You Should Know About Pitted Keratolysis

   Pitted keratolysis (PK), originally called “keratoma plantare sulcatum” by Castellani in 1910, first presented in those who went barefoot during the rainy season in tropical areas.1 Acton and McGuire renamed the disease “keratolysis plantare sulcatum” since the condition is actually a partial loss of the stratum corneum rather than a hyperkeratosis as Castellani’s “keratoma” implied. 2 We see it mostly in athletes who spend prolonged times in occlusive footwear or in those who work in very wet environments.

   Sulfur containing compounds produced by the bacteria lead to the malodor. The pungent odor has lead to a new name of “toxic sock syndrome.” 3

   Pitted keratolysis is caused by a cutaneous infection with either Micrococcus sedentarius (now renamed as Kytococcus sedentarius), Dermatophilus congolensis and the Corynebacterium species. 4 Other organisms that can cause this infection include Actinomycetes keratolytica and Streptomyces.

   These superficial bacterial “infections” occur in the stratum corneum and are associated with overgrowth of normal flora at sites of occlusion and high surface humidity. They are non-inflammatory in appearance. 4

   The human skin harbors a complex microbial ecosystem with transient, short-term resident and long-term resident biota, based on the consistency with which they are isolated. Staphylococcus, Micrococcus, Corynebacterium, Brevibacteria, Propionibacteria and Acinetobacter species, among others, are regularly cultivated from normal skin. 5

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