Pitted keratolysis is a poorly studied infectious disease of the skin of the feet that occurs against the background of hyperhidrosis. Clinically characterized by the appearance of painless point-shaped funnel-shaped erosions up to 8 mm in size. Erosions form drainage foci that occupy a significant surface of the foot and exude an unpleasant odor. Rashes may be accompanied by a burning sensation and itching. Typical localizations are the heel area, the interdigital spaces and the pads of the toes. They are diagnosed clinically, microscopically and histologically, and the material is seeded on nutrient media. Treatment is complex antibacterial and antihyperhydrosis. The result depends on the accuracy of the diagnosis.
Pitted keratolysis is an infection of the skin of the feet caused by coccoid flora and Pseudomonas aeruginosa and manifested by damage to the stratum corneum of the epidermis with the formation of erosions with a fetid odor. It is assumed that the smell is a consequence of the formation of sulfur compounds against the background of sweating and high humidity. The depth of the primary erosive elements depends on the thickness of the stratum corneum. The disease was first described in the early twentieth century under the name “black keratomycosis”, since then the understanding of the essence of dermatosis has radically changed. It has been scientifically proven that pitted keratolysis is not related to dermatomycosis, but the vicious perception of nosology as mycotic persists, which is facilitated by the frequent combination of pitted keratolysis with different types of foot mycosis.
Pittedl keratolysis of the feet is endemic, occurs mainly in countries with hot climates. Mostly affects young men. There is no seasonality. In domestic dermatology, this nosology is not given sufficient attention, although in Russia, small-point keratosis accounts for more than 10% of all infectious diseases of the feet. Athletes and the military are particularly often affected. Due to the similarity of clinical symptoms, practicing dermatologists often mistake pitted keratolysis for mycosis of the feet, which leads to erroneous diagnosis and incorrectly prescribed therapy. The urgency of the problem is associated with the prevalence of the disease in socially significant groups of the population: among military personnel, athletes.
The causative agent of pitted keratolysis is cocci, Pseudomonas aeruginosa, or (more often) an association of these microorganisms. Micrococci are very small gram–positive microbes that, singly or in groups, are ubiquitous in nature, in the air, in food and on the skin. They are not pathogenic microorganisms. Without carrying a direct threat to the skin, micrococci produce specific proteolytic enzymes such as keratinase on the surface of the stratum corneum of the epidermis, capable of easily dissolving corneal cells with the formation of distinctly noticeable point erosions. After the formation of defects, micrococci, which are an extremely sedentary type of cocci, fill the erosive surfaces, thereby preventing their healing.
The mechanism of development of pitted keratolysis caused by Pseudomonas aeruginosa differs from the one described above. This bacterium is very mobile and needs the obligatory presence of oxygen for its development. By isolating an enzyme that lyzes the stratum corneum of the epidermis and provokes the formation of crater-like point erosion, Pseudomonas aeruginosa does not settle on the damaged area on a permanent basis, but migrates from defect to defect, preventing erosions from epithelizing. With the long-term existence of erosions, inflammation joins, in which dermal cells, lymphocytic cells of general and local immunity take part. Lymphocytes of the immune system partially correct the decrease in immunity that occurred during the course of dermatosis and stimulate the development of the inflammatory process in the dermis. Dermal cells are actively involved in the process of pathogen phagocytosis and tissue proliferation to replace skin defects.
As a result of these processes, old defects are delayed, but new ones appear nearby, a kind of vicious circle turns out, which can be broken only with special antibacterial therapy. The course of pitted keratolysis aggravates hyperhidrosis, which is a compensatory reaction of the body to the temperature conditions of the environment. When the patient stays at elevated temperatures, the thermoregulation center sends signals to the sweat glands, the glands produce moisture, creating a protective film on the skin surface. With prolonged increased sweating and the presence of defects, the condition of the skin changes, its barrier properties decrease, secondary infection joins, most often mycotic.
Clinical manifestations of pitted keratolysis are very similar to mycotic lesions of the feet. The primary element of the disease is cone-shaped point erosion, the depth of which depends on the thickness of the stratum corneum of the soles (usually 1-8 mm). The elements are symmetrically located in the places of dead spots, on the areas of the foot exposed to constant pressure, and on the rubbing surfaces between the toes. Sometimes rashes are joined by itching and burning of the skin. If the erosions are accompanied by increased sweating, that is, they are located inside the water protective film, they undergo maceration, acquire a whitish hue.
Point erosions tend to merge and eventually form erosive surfaces up to several centimeters in diameter. Skin defects usually do not cause any particular inconvenience, since they do not cause pain. The reason for going to the doctor, as a rule, is an unpleasant smell. The source of the odor is bacteria that actively multiply on the surface of the skin of the feet in a warm and humid environment. It should be noted that in the absence of treatment, pitted keratolysis can last indefinitely. With a prolonged course, casuistic cases of palm skin lesions are described.
The diagnosis of pitted keratolysis is carried out by a dermatologist based on clinical data, examination of the affected areas under a Wood lamp (luminescent diagnostics), control skin scraping in the area of defects to exclude mycotic infection, sowing on nutrient media to detect combined coccal and pseudomonasal (pseudomonasal) infection. Histomorphology gives a picture of point keratolysis of the epidermis and colonization by pathogens of point microerosions. Pitted keratolysis is differentiated with mycosis of the feet, plantar warts, basal cell nevus, arsenic poisoning, candidiasis, erythrasma and interdigital maceration.
Pitted keratolysis treatment
The basis of successful therapy is the correct diagnosis of the disease with the exception of the mycotic nature of the disease. A dermatologist, a physiotherapist and a cosmetologist take part in the treatment of pathology. Therapy of pitted keratolysis is complex, priority is given to pathogenetic measures. First of all, it is necessary to eliminate the cause that provoked the occurrence of the disease. To do this, a course of therapy with antibiotics from the group of macrolides is carried out. The funds are used internally and externally. Ointments, solutions and powders with the same active principle are used, as well as benzoyl peroxide preparations. Special attention is paid to hyperhidrosis. To eliminate excessive sweating, spot injections of the neurotoxin complex botulinum toxin type A, capable of paralyzing the glandular apparatus, are performed in the area of the sweat glands. If there are contraindications to this manipulation, it is replaced by physiotherapy: ionophoresis, electrophoresis with preparations based on silver or aluminum chloride.
It requires daily compliance with certain rules. It is necessary to wash your feet with deodorizing soap as often as possible, refuse to wear tight shoes, use activated carbon adsorbents when wearing shoes, never wear shoes made of synthetic materials, choose cotton socks and breathable insoles. In summer, barefoot walking on grass is encouraged as a preventive measure to eliminate the sealed environment of bacterial reproduction. Patients with pitted keratolysis are contraindicated in a hot, humid climate. Moving to temperate latitudes is not excluded. If these recommendations are followed, the prognosis of fine-point keratolysis is favorable.