Tropical mycoses: causes, symptoms, diagnosis, treatment

Mycotic skin lesions are a very significant practical problem, both because of their extreme prevalence and their known contagiousness. This is even more true of tropical dermatomycosis, which, like all tropical pathology, can be divided into tropical flies, which occur exclusively in hot climates, and cosmopolitan dermatomycoses that acquire their distinctive, sometimes very pronounced clinical, epidemiological features.

As an example, among such very common cosmopolitan mycoses, superficial fungal skin lesions, or keratomycosis, whose bright representative are various variants of multicolored, or otrigious lichen, should be mentioned.

What causes tropical dermatomycosis?

Today it is finally established that the lipophilic fungi of the genus Malassezia, with certain predisposing factors, are the main etiological factor of the multi-colored lichen. Incidentally, it should be said that Malassezia spp. can play an etiopathogenetic role in a very wide range of pathological processes in children and adults, healthy individuals and immunodeficient conditions - folliculitis, seborrheic dermatitis, neonatal pustulosis, onychomycosis (often recorded in South America), external and middle otitis media, draining papillomatosis, and, possibly, psoriasis of the scalp.

Tropical yellow lichen

A bright representative of the multi-colored lichen in a hot climate is tropical yellow lichen, caused mainly by Malassezia furfur, which refers to keratomycosis and is characterized by the appearance, mainly on the skin in the face, neck, less often in other areas, small yellowish orange spotted rashes. The independence of this keratomycosis is not recognized by all, and therefore it is more convenient to attribute it to one of the varieties of colorful lichen.

Most often, yellow lichen occurs in tropical and subtropical countries of Southeast Asia, South America and Cuba, less often - on the African continent. The disease has a pronounced seasonal character and occurs usually in the season of maximum humidity. Not only adults are ill, but also children, among whom group diseases can be observed .

Symptoms of tropical yellow lichen are characterized by the appearance on the skin of the face and neck initially small in size and irregular outlines of yellowish spots, with a slight orange tinge. As far as peripheral growth, they merge, forming large spots with more or less cyclic outlines of a spot on the surface of which a slight peeling is observed. Subjective sensations are absent.

Tropical black lichen

As a variant of tropical keratomycosis, tropical black lichen (tinea nigra) with the corresponding color of spots is considered, which also have a favorite localization on the skin of the face. In addition, the classical varieties of varicoloured lichens with a typical localization and a tendency to extensive lesions are very widespread in tropical conditions.

Piedra

Of the group of fungal hair lesions, or, to typical representatives of tropical fungal infections, a piedra can be attributed. This trichomycosis is characterized by the development on the hair of small multiple or single dense nodular formations, which are fungal colonies, muff-shaped surrounding hair. The piedra occurs mainly in Central and South America, more often in Colombia, Argentina, Brazil, Paraguay and Uruguay. Individual cases have been reported in South-East Asia, Japan and some other countries. The causative agents of the piedra are representatives of the genus Trichosporon, in particular, with the white piedra Tr. Giganteum, Tr. Cerebriforme, Tr. Ovale i dr.

Causes of the piedra

Pathogenetic factors contributing to the development of the disease are high temperature and humidity of the environment, certain social and living conditions. For example, certain national customs, in particular, lubrication of hair when laying them with vegetable oils and fermented milk products, are of some importance. Conditions that are permanently created with this method of hair styling (at a high ambient temperature and humidity) are close to thermostatic conditions for the development of the fungus. A regularity is also the fact that the piedra occurs mainly in individuals with straight long hair and, less often, with short and curly hair. Apparently, therefore, the piedra is practically not found on the African continent. People of both sexes can be ill, although it is more often found in young women.

[1], [2], [3], [4], [5]

Symptoms of the piedra

Symptoms of the piedra are characterized by the presence on the hair in the head region of multiple to 20-30 and smaller and very solid nodules that are particularly well visible through the lens. They have the appearance of irregular, oval or fusiform formations, covering the hair in the form of an almost complete ring. In some cases, as a result of the fusion of close-lying nodules, the hair appears surrounded by a solid muff. There are two main types of piedra: black and white.

The tropical, or black, piedra is characterized by a brownish or rich brown color of the nodules, which are easily detected palpably when carrying the hair between the fingers. Sometimes in neglected cases, tightly stretched hair due to the gluing of the nodules closely adjoin each other and form whole bunches of affected hair, which is often called a Colombian colt. However, even in such severe cases, the hair itself is practically not affected, since the spores are found only on the hair, not penetrating into the interior and thus affecting the cuticle, so the hair struck by the pedicle never breaks off.

Somewhat different is the white piedra, which, besides the South American countries, is also found in the countries of Asia and Europe. White piedra can be observed in men in the area of growth of the beard and mustache, in women - on the scalp, pubic region and in the armpits. Nodules with a white piedra have light colors with grayish-yellow and milky-matt shades, they are not as stony as in the black piedra. The size of couplings with a white piedra sometimes reaches 7-10 mm.

Diagnostics of the piedra

Diagnosis of the piedra as a whole is not difficult and is based on typical clinical manifestations.

[6], [7], [8]

Treatment of the piedra

The most radical way to treat the piedra is to cut the hair that is affected by the fungus. It is also possible to use special therapeutic shampoos, containing in the required concentration of antimycotics, mainly from the azole group.

Imported trichomycosis

A particular problem in the context of tropical dermatomycosis may be the possible risk of importing a tropical infection into countries with a temperate climate. An example of such an imported fungal infection from a group of trichomycosis can serve as some variants of superficial trichophytosis of the scalp, which in general is known to belong to one of the most contagious forms of trichomycosis. Excreted pathogens in such imported cases are most often classified as Trichophyton soudanense and are "imported" usually from countries of the African continent. The clinical picture of such trichomycosis practically does not differ from that of the usual "ringworm". All the more important is the necessary alertness of the dermatologist for this diagnosis in a patient who has come from tropical countries.

Chronic candidiasis of skin and mucous membranes

Candida fungi are a very common infection that can acquire special significance in a tropical climate, where the most favorable conditions for their growth and reproduction are formed. Lesions of the skin and mucous membranes caused by Candida spp., Acquire in these conditions quite often a chronic, widespread character. An example is chronic candidiasis of the skin and mucous membranes, combining the simultaneous damage of these structures. The skin becomes erythematous-infiltrated, covered with crusts and vegetations. The adjacent sections of the mucous membranes are brightly hyperemic, covered with a white coating, often with the phenomena of granulomatosis.

A special tendency towards the endemicity of candidiasis of the skin and mucous membranes, as is known, does not exist and is found everywhere. However, in addition to the high temperature and humidity in the tropics, the spread of this fungal infection can be largely promoted by hypovitaminosis, which is characteristic of a number of countries in this belt.

For conventional dermatomycosis, in which Tr is recognized as a frequent pathogen . rubrum, in the conditions of the tropics, the rapidly developing prevalence of lesions on large areas of the skin with the involvement of facial skin is characteristic.

In addition, in recent years, European countries have registered a marked increase in the number of imported fungal infections with the usual clinical picture, but with atypical pathogens for temperate climate. There is an opinion that this is due not only to migration processes, but also can occur by simple physical transfer of the pathogen along transport routes. In particular, superficial dermatomycosis caused by Scytalidium dimidiatum is diagnosed in recent years in Europe by streets coming from countries of Southeast Asia and Oceania. The clinical symptoms of this fungal infection are very similar to the symptoms of hyperkeratotic mycosis of the feet, but many details of it are not yet known, including the mechanism of transmission. Since many cases of mycotic infection are asymptomatic in the initial stages of development or may resemble other diseases, special attention is required to increase the ability to diagnose such a fungal infection.

Of particular interest from the point of view of tropical dermatology are deep mycoses, which are known to be very common in hot countries. The most striking example of this group is Maduromycosis.

[9]

Maduromycosis

Madura disease or the Madurian foot (mycetoma) is one of the classic representatives of severe and long-lasting deep mycoses of tropical countries with a predominant lesion of the feet and shins.

The disease is known for a long time - its first description is attributed to the beginning of the XVII century. Maduromycosis is found in many countries of the world with conditions of a tropical or subtropical climate: it is practically all countries of Southeast Asia, many countries of Africa and South America. Sporadic cases can also occur in some European countries with a temperate climate. Many dermatologists tend to think of maduromycosis as a polyethylene disease, as the fungi that are detected in different cases belong to the most diverse families, genera and species: Actinomyces, Nocardia, Aspergillus, and others.

Causes of Madura's disease

In general, the causative agents of maduromycosis can be referred to conditionally pathogenic organisms. They are widespread in nature, especially in tropical climates. The main path of infection is exogenous, and traumas, for example, spines or sharp endings of plants or simply walking barefoot on contaminated soil, contribute to penetration of the pathogen.

[10], [11], [12], [13], [14]

Symptoms of Madura's Disease

Most often the process begins in the area of the feet, somewhat less often - in the region of the shin. At the site of penetration of the causative agent there is a single small size up to the pea nodule, with palpation dense and somewhat painful. As the nodes increase and spread after a few months, softening begins in their central part, and there is a fluctuation. In the end, the abscess is opened with the formation of fistulas, from which a pus-like one with a fetid odor separates, containing a mushroom-like fungus visible to the naked eye 2-3 mm in size, similar to caviar. The color of these druses can be different - white, yellow, black, sometimes red, which depends on the pigment that fungi are harvested at different phases of their development.

Within 3-4 years the process slowly spreads both to healthy areas, and to deeper layers of the skin, subcutaneous tissue, up to the defeat of bones. The foot becomes enlarged in size, tuberous, sharply deformed, sometimes becoming a formless mass. The arch of the foot is smoothed out, the fingers seem to turn upward, the lower leg, on the contrary, appears markedly thinned.

Diagnosis of Madura's disease

Diagnosis of maduricosis in typical cases is not difficult and is based on the basis of typical clinical manifestations. In some cases it is necessary to carry out a differential diagnosis with actinomycosis.

[15], [16],

Treatment of Madura's disease

In prognostic attitude, maduromycosis does not refer to diseases with severe prognosis, even cases of self-healing are known. However, developing deformities of the foot and bone lesions may require surgical intervention, up to the amputation of the foot.

Sporotrichosis

Another tropical mycosis - sporotrichosis - is a chronic disease of the group of deep mycoses with lymphogenous lesions of mainly the skin, subcutaneous tissue and less often other organs and systems. Most often sporotrichosis occurs in South America, primarily in Mexico, somewhat less often - in countries of Africa and South-East Asia.

What causes sporotrichosis?

Sporotrichosis is caused by various species of fungi of the genus Sporotrichon. As saprophytes, they are widely distributed in nature, in soil, on plants, vegetables, flowers, etc. The existence and distribution of them in nature contribute to high temperature and humidity. The defeat of man, according to most researchers, occurs exogenously, most often after injury to the skin and less often - the mucous membranes. People are sick at any age and of any gender. Localization of rashes is associated with open areas of the body that are often injured: hands, feet, forearms, sometimes face. There are usually two clinical forms of sporotrichosis: localized and disseminated. The localized form is sometimes called lymphatic, and it occurs more often than disseminated.

Symptoms of sporotrichosis

Initially, at the site of penetration of the pathogen, a slight acne develops, which then becomes a typical ulcer. Sometimes everything at once can begin with a gummy node. A knot or knot, initially the size of a pea, dense and painless, begins to gradually increase in size and takes the form of a hemispherical tumor. The formation is soldered with subcutaneous fat, the skin over it becomes inflamed, acquiring a dingy-cyanotic shade and, necrotizing, turns into an ulcer. This whole process takes quite a long time. Sometimes this primary affect of sporotrichosis is called sporotrichoznym chancre. It is usually single, but it is possible that there are three or five foci at the same time.

Gradually, regional lymphatic vessels are involved in the process, and linearly located bands appear on the skin. Palpatorally, they are probed in the form of strands with clear-cut thickenings. A characteristic feature is a complete absence of pain even after palpation. Later on, sometimes linearly located secondary nodes may appear along the course of the affected lymphatic vessel, some of them do the same development cycle as the primary affect.

The localized form of sporotrichosis is characterized by a benign course. Sporotrichosis occurs in a satisfactory state without marked changes on the part of the blood. Some authors describe acne-like manifestations of sporotrichosis, which initially can simulate vulgar acne, especially their conglobate varieties.

Diagnosis of sporotrichosis

In typical cases, the diagnosis of localized sporotrichosis is not difficult. However, in doubtful situations, the diagnosis can be confirmed by a culture method.

[17], [18], [19], [20], [21], [22], [23]

Deep Mycoses of Tropical Regions

To frequent deep mycoses of tropical regions is also South American blastomycosis, or Brazilian blastomycosis.

This representative of deep mycoses occurs mainly on the South American continent and is characterized by a torpid current with the development of a ulcerative-granulomatous lesion not only of the skin but also of the mucous membranes, sometimes involving the internal organs, gastrointestinal tract and lymph nodes. The causative agent of the disease is currently recognized as Blastomyces braziliensis, close to the blastomycetes of North American blastomycosis. It is assumed that the pathogen enters the human body in an exogenous way. However, the role of the endogenous pathway of infection is also not excluded.

[24], [25], [26], [27], [28], [29]

South American blastomycosis

South American blastomycosis occurs exclusively in the climatic conditions of hot countries. The main endemic region is Brazil. It also occurs in other countries of Central and South America. People usually get sick of young and middle age, somewhat more often - men. Typically, a localized and less commonly generalized form is described. Among the localized forms, skin, skin-mucous and visceral are secreted.

At the site of penetration of the pathogen first there are grouped papular eruptions. Sometimes the disease begins immediately with a clinical picture of angina or ulcerative stomatitis. Gradually, within a few months, a fairly extensive dense infiltrate is formed, which gradually softens and undergoes central necrosis with superficial ulceration. The surface of ulcers is covered with granulations, but growth continues both deep and peripherally, capturing large areas of the mucous membrane of the oral cavity, throat, nasopharynx with the transition to the more distant parts of the mucous membranes and the skin. At the same time, the reaction from the regional lymph nodes develops: they grow, become painful and welded together and with the underlying tissues. In the future, without treatment as a result of the generalization of the process, the disease takes on an increasingly systematic character.

Diagnosis of South American blastomycosis is based on typical clinical manifestations and laboratory data, including culture studies. The prognosis in the absence of treatment is not always favorable, and the disease can end up lethal.

Treatment of tropical dermatomycosis

Treatment of tropical dermatomycoses as well as their analogues from temperate climate is usually carried out by external antimycotics, mainly from the group of azoles or terbinafine. In the case of extensive lesions of the skin in keratomycosis, the systemic use of antimycotics is indicated.

Treatment of tropical skin mycoses

In general, the treatment of tropical skin mycoses with modern powerful antimycotic agents of systemic and external action is in most cases quite successful. The choice of the specific antimycotic will depend both on the clinical picture of the fungal skin lesion and the individual characteristics of the patient, as well as on the capabilities of the local pharmaceutical market.