[Dr.Anisimova]

Tropical Dermatology Roberto Arenas
Department of Dermatology
Dr. Manuel Gea Gonzalez General Hospital
Mexico City, Mexico
Roberto Estrada
Dermatology Service of the General Hospital of Acapulco
Acapulco, MexicoGEORGETOWN, TEXAS
U.S.A.2001
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Pitted Keratolysis
Roberto Arenas
Pitted keratolysis is also known as tropical plantar keratolysis. It is a superficial
infection that affects the horny layer. It is localized on the soles, and it is characterized
by punctiform depressions and asymptomatic superficial erosions caused by
organisms from the genders Corynebacterium, Dermatophilus and Micrococcus.
Humidity and macerated skin favor its growth.
GEOGRAPHIC DATA
Distribution is worldwide. It affects equally all races and both sexes. It
predominates in the tropics and is more frequent in those who walk barefoot,
have their feet exposed to water, or suffer from hyperhidrosis. The incidence is
also high in those who use boots or sports shoes such as soldiers and athletes.
ETIOLOGY
Infection is caused by actinomycetes as well as other organisms. It is possible
that the casual agent has not been determined and that the proposed microorganisms
like Corynebactirium sp, Dermatophilus congolensis and Micrococcus
sedentarius act synergistically (Arch Dermatol 1972; 105:580-584). Friction,
occlusion and maceration favor infection of the horny layer. Pigment changes
and the fetid odor are related to the microorganisms involved and depend upon
the mixture of thiols, sulfurs, and thioesters. It has been suggested that M.
sedentarius generates the erosions by the production of two proteinases in the
presence of hyperhydration and alkaline pH (J Appl Bacteriol 1992; 72(5): 429-34).
D. congolensis secretes keratinases that can digest the keratin (Med Microbiol
Immunol Berl 1991; 180(1):45-51).
CLINICAL PICTURE
It is seen on the soles of the feet. It predominates in weight-bearing areas, and
it can be unilateral or bilateral (97%). It is rarely seen on the palms. The dermatosis
is composed either of punctiform depressions or superficial erosions of 1-3 mm
that form rows that coalesce into circular lesions or irregulars lesions of geographic
appearance. Their color is gray, greenish, or brownish, and they
appear filthy (Fig. 7.1). Rarely there are erythematoses, and painful lesions or tinea
pedis. There is a rare hyperkeratotic form (keratoma plantare sulcatum). Its existence
is moot. It appears as circinated zones of hyperkeratosis on the plantar arc of
the feet, and it can be observed as small depressions. It can be associated with
other forms of palmoplantar keratoderma.
LABORATORY DATA
Curetted lesions can be Gram stained. Biopsy by shaving is recommended. A
crater-like lesion is observed. It is 0.5-3 mm with well-defined walls that are vertically
cut. There are septated filaments of 0.5-1.5 µm and gram positive
diphtheroides are seen. They are basophilic with hematoxylin and eosin stain, but
are better observed with Gomori-Grocott and PAS (Fig. 7.2). They are not acid-fast.
On the surface one finds an opaque material that can be dirt.
TREATMENT
The elimination of predisposing factors is important. Drying powders or powder
to control hyperhidrosis can be used. Aluminum chloride 10-20% is useful, as
well as Whitfield’s ointment (vaseline with benzoic acid 6% and salicylic acid 3%),
clioquinol 3%, benzoyl peroxide 5%, or topical antibiotics like clindamycin,
erythromycin, mupirocin, or fusidic acid can also be used. Formaldehyde 1% in
aqueous solution is very efficient, and good results are observed in one or two
weeks.
SELECTED READINGS
1 Arenas R. Jimenez R, Diaz A et al. Queratolisis punteado. Estudio
clinico-epidemiologico, histopatologico, y microbiologico en 100 pacientes
(Pitted Keratolysis. The clinical-epidemiologic, histopathologic, and microbiologic
study in 100 patients) Dermatologya Rev Mex 1992; 36(3):152-58).
2 Shah AS, Kamino H, Prose NS. Painful, plaque-like, pitted keratolysis occurring
in childhood. Pediatr Dermatol 1992; 9(3): 251-54).