Background
Pitted keratolysis is a skin disorder characterized by crateriform pitting that primarily affects the pressure-bearing aspects of the plantar surface of the feet and, occasionally, the palms of the hand as collarettes of scale. The manifestations of pitted keratolysis are due to a superficial cutaneous bacterial infection. [1, 2]
Pitted keratolysis has gone through several name changes. [3, 4] Pitted keratolysis was described initially in the early 1900s as keratoma plantare sulcatum, a manifestation of yaws. Pitted keratolysis was identified in the 1930s as a unique separate clinical entity, and the name was changed to keratolysis plantare sulcatum. The current name, pitted keratolysis, describes the clinical presentation well and has remained the modern nomenclature to describe this entity.
Pathophysiology
Pitted keratolysis is caused by a cutaneous infection with Micrococcus sedentarius (now renamed to Kytococcus sedentarius); Dermatophilus congolensis; or species of Corynebacterium,Actinomyces, or Streptomyces. [5, 6, 7, 8] Under appropriate conditions (ie, prolonged occlusion, hyperhidrosis, increased skin surface pH), these bacteria proliferate and produce proteinases that destroy the stratum corneum, creating pits. [9] D congolensis liberates keratinases in appropriate substrate. [10, 11, 12] K sedentarius has been found to produce 2 keratin-degrading enzymes. They are protease P1 (30 kd) and P2 (50 kd). [8] The malodor associated with pitted keratolysis is presumed to be the production of sulfur-compound by-products, such as thiols, sulfides, and thioesters. [13]
In 2006, foot odor without pitted skin changes was discovered to be from overgrowth of Bacillus subtilis and specifically an isovaleric acid produced by Staphylococcus epidermidis overgrowth, a normal skin flora. [14]
It is a common problem among athletes, as heat, sweat, and humidity cause changes in the skin microbiome. [15, 16, 17]
Epidemiology
Frequency
United States
Pitted keratolysis occurs worldwide. Pitted keratolysis can be seen in both tropical and temperate environments, and it can be related to occupation or sport activity. [18, 19] A study of 142 homeless men in the Boston, Mass area revealed that 20.4% of 142 examined patients had pitted keratolysis. [20]
International
International incidence rates of pitted keratolysis vary significantly based on the environment and occupation. Prevalence rates of pitted keratolysis have ranged from 1.5% of 4325 Korean industrial workers [21] to 2.25% (11 of 490 subjects randomly evaluated) in New Zealand. [6] In addition, 2.6% of 378 Turkish male adolescent and postadolescent boarding school students had pitted keratolysis, [22] and, in a 2-year study from Belgium, only 4.8 cases of pitted keratolysis occurred per 1000 dermatology visits. [23] In a study of 1012 patients with atopic dermatitis from Nigeria, only 19 (1.8%) had pitted keratolysis. [24] However, 66 (23.3%) of 283 Korean coal miners [21] and 341 (42.5%) paddy field workers in costal South India had pitted keratolysis due to persistent exposure to moist environments. [25]
In the tropical military setting, where heat, humidity, and boots combine to produce a microenvironment that predisposes to pitted keratolysis, prevalence rates are much higher. Of the 387 volunteer United States soldiers evaluated in South Vietnam, 53% had pitted keratolysis. [26] However, the incidence of pitted keratolysis in all military soldiers may not be so high because only 108 (12.8%) of 842 Korean soldiers were diagnosed with pitted keratolysis. [27] In 184 German athletes examined, 25 (13.5%) had pitted keratolysis. [15]
Race
No race predilection is reported for pitted keratolysis.
Sex
Theoretically, both males and females should be affected by pitted keratolysis; however, most written case reports or studies have involved male patients.
Age
Pitted keratolysis can affect patients of any age.
Prognosis
Pitted keratolysis is cured easily and has an excellent prognosis. No mortality is associated with pitted keratolysis. However, the excessive foot odor from this disorder may be socially unacceptable. Pitted keratolysis may be symptomatic; producing secondary painful feet, which can limit function. [28, 29] In 2005 in Turkey (East region), a study of dermatologic manifestations in 88 hepatitis B surface antigen carriers compared with 84 controls demonstrated a significantly higher prevalence of oral lichen planus and pitted keratolysis. [30] The mechanism is unknown and further studies are needed to confirm this association.
Patient Education
Educate patients with pitted keratolysis about the etiology of the disorder and regarding ways to prevent and treat pitted keratolysis. See Medical Care.
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A large plaque-like lesion of Pitted keratolysis on the large toe.
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A case of inflammatory pitted keratolysis
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Pitted keratolysis with hyperkeratosis on the heel.
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Classic pits of pitted keratolysis on the plantar aspect of the phalanges.
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Pitted keratolysis forming sulci on the heel.
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Histopathology reveals a crater limited to the thick stratum corneum of the epidermis.
