Derm Dx: Smelly feet with crater-like depressions - Clinical Advisor

Derm Dx: Smelly feet with crater-like depressions

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  • Pitted keratolysis 1_1113 Derm Dx

  • Pitted keratolysis 2_1113 Derm Dx

  • Pitted keratolysis 3_1113 Derm Dx

  • Pitted keratolysis 4_1113 Derm Dx

A 55-year-old patient presents with his wife, who complains that his feet smell “terrible.”

Pitted keratolysis (PK) is a non-inflammatory gram-positive bacterial infection of the palmoplantar skin that is commonly associated with hyperhidrosis and malodor. On physical exam, small 1 mm to 7 mm crater-like depressions are found within the stratum corneum on weight-bearing...

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Pitted keratolysis (PK) is a non-inflammatory gram-positive bacterial infection of the palmoplantar skin that is commonly associated with hyperhidrosis and malodor.

On physical exam, small 1 mm to 7 mm crater-like depressions are found within the stratum corneum on weight-bearing regions of the soles, including the heels, balls of the feet and plantar great toes.

PK lesions may also be observed on the palms, albeit rarely. The pits can coalesce into larger superficial erosions of the stratum corneum.

The condition may be associated with itching and a burning sensation in some patients. Because there is usually no associated erythema, the condition often goes unnoticed and untreated.

One of the risk factors for developing PK is hyperhidrosis; hence, PK occurs worldwide in the hot and humid climates. Prolonged occlusion and increased skin surface pH are other predisposing factors.

PK is most commonly caused by Kytococcus sedentarius. However, other bacteria, such as Dermatophilus congolensis, Corynebacterium and Actinomyces spp. can be involved.

K. sedentarius produces two serine proteases, K1 and K2, which degrade keratin in the stratum corneum. The bacteria release sulfur-containing compounds that lead to the characteristic associated malodor.

Diagnosis

The diagnosis of PK is usually clinical. Characteristic features such as hyperhidrosis and malodor make the diagnosis easier, but biopsy will reveal keratin pits lined with bacteria.

Other answer choices:

Keratolysis exfoliativa (KE) is a palmoplantar dermatosis characterized by air-filled blisters that lead to a delicate collarette of desquamation.

Palmoplantar keratoderma (PPK) constitutes a heterogeneous group of disorders characterized by thickening of the palms and the soles. The PPKs can initially be divided based on whether they are inherited or acquired.

The three forms of inherited PPKs are diffuse, focal and punctate. Diffuse PPK consists of uniform involvement of the palmoplantar surface and is usually evident within the first few months of life. Focal PPK consists of localized areas of hyperkeratosis, located mainly on pressure points and sites of recurrent friction. Punctate keratoderma features multiple small, hyperkeratotic papules, spicules or nodules on the palms and soles. These can be classified further as isolated or as keratodermas with other associated features.

There are many causes of the acquired forms of PPK, including drugs.

Darier disease is an autosomal dominant disease characterized by a chronic, waxing and waning course of eruptions involving the scalp, face, neck, trunk and extremities, with accentuation in the seborrheic areas. The lesions consist of tan, pink and brown, rough-feeling papules. These papules may coalesce into large plaques, which can become secondarily infected and result in crusting and weeping.

The eruptions start in childhood and last a lifetime. The palms and soles may have punctate keratoses. Skin biopsy is diagnostic, demonstrating epidermal suprabasilar clefts with acantholytic keratinocytes.

Treatment and prognosis

PK treatment consists of controlling the hyperhidrosis using aluminum chloride 20% solution, or (in recalcitrant cases) botulinum toxin, as well as topical antibacterial agents such as erythromycin or clindamycin.  

Prognosis is very good. Rapid resolution is expected with appropriate treatment. Patients should be taught about the etiology of PK in order to avoid recurrence. Helpful preventative strategies consist of advising patients to avoid occlusive footwear, use moisture-wicking socks and change sweaty socks frequently.     

Nelly Song is senior medical student at Baylor College of Medicine.  

Adam Rees, MD, is a graduate of the University of California Los Angeles School of Medicine and a resident in the Department of Dermatology at Baylor College of Medicine also in Houston.

References

  1. Bolognia J, Jorizzo J, Rapini R. Dermatology. St. Louis, Mo.: Mosby/Elsevier, 2008. pp 1201-1202.
  2. Babcock M, Usatine RP. “Chapter 112. Pitted Keratolysis.” In: Usatine RP, Smith MA, Chumley H, Mayeaux, Jr. E, Tysinger J, eds. The Color Atlas of Family Medicine. New York: McGraw-Hill; 2009.
  3. Chang YY. “Keratolysis exfoliativa (dyshidrosis lamellosa sicca): a distinct peeling entity.” Br J Dermatol. 2012;167(5):1076-84.
  4. “Keratosis Palmaris Et Plantaris.” Keratosis Palmaris Et Plantaris. Web. 19 Sept. 2013. Available at http://emedicine.medscape.com/article/1108406-overview.
  5. Marks J. Principles of Dermatology. 5th ed. London: Elsevier, 2013. pp 103.
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