Skin tuberculosis is a severe infectious disease that has a long course with frequent relapses, due to the colonization of the skin and subcutaneous tissue with Mycobacterium tuberculosis. The symptoms of this condition are extremely diverse, for this reason, some researchers believe that mycobacteria are the cause of a whole group of dermatological pathologies. Diagnostics includes a dermatological examination, determination of the presence of antibodies to the causative agent of tuberculosis in the blood, examination of the skin lesions. Treatment is carried out with traditional anti-tuberculosis drugs, as well as supportive and immunostimulating agents.
Skin tuberculosis is an extremely diverse pathology in its manifestations, course and prognosis caused by mycobacteria that penetrate the skin from the external environment or already existing foci in other organs. Various forms of tuberculosis (lungs, bones, skin) have been familiar to man since ancient times. However, little was known about the causes of this disease until Robert Koch discovered Mycobacterium tuberculosis in 1882, and then isolated the protein tuberculin from them, which is used to diagnose this pathology to this day. Shortly after the works of R. Koch began explosive progress in the study of tuberculosis, its diagnosis and treatment.
Skin tuberculosis to a lesser extent than the pulmonary form of the disease is a social problem of our time. Although in a number of countries there is a slow increase in the prevalence of this pathology. The main problem also lies in the fact that not every dermatologist can diagnose skin tuberculosis in a timely and correct manner. This is facilitated by the slow development of manifestations and their significant variability – most patients are diagnosed no earlier than 4-5 years after the onset of the disease. Late diagnosis also leaves its mark on treatment, which becomes lengthy, complex and has controversial and variable results.
The cause of any tuberculous lesion is Mycobacterium tuberculosis, which has several subspecies. At the same time, human, bovine and (according to some sources) avian varieties of the pathogen are capable of causing skin tuberculosis. The disease is less common relative to other forms of tuberculous lesions, since the skin of a healthy person is an unfavorable environment for the development of mycobacteria. It is not known exactly why the pathogen is able to colonize the skin and subcutaneous tissue – the influence of endocrine, immunological and other disorders is assumed. It has been noticed that the reduction or absence of insolation (exposure to ultraviolet rays of sunlight on the skin) dramatically increases the risk of developing skin tuberculosis.
Mycobacteria can get into the skin tissues in many ways, they are all divided into endogenous and exogenous ways of infection. For the development of endogenous skin tuberculosis, it is necessary to have an infectious process in other organs – lungs, bones, intestines. In this case, the pathogen can enter the skin by hemato- or lymphogenically and cause the disease. With an exogenous method of infection, mycobacteria enter the skin from the external environment – this path is considered much rarer. Basically, butchers, veterinarians, and sometimes phthisiologists suffer from exogenous skin tuberculosis.
After Mycobacteria enter the skin tissues, their reproduction begins with the development of a characteristic granulomatous inflammation. The depth of the foci, their size, number, localization in skin tuberculosis vary greatly in various forms of the disease. In some cases, the main role in the pathogenesis of the disease is played by an allergic component, in which case it is said that there is hyperergic skin tuberculosis. As a rule, this form is characterized by an abundance of nonspecific manifestations characteristic of allergic and autoimmune vasculitis. The allergic component is more or less pronounced in almost a third of all cases of skin tuberculosis.
There are many clinical forms of skin tuberculosis, which are very different from each other. This gives rise to some experts to argue that mycobacteria cause not one pathology of different types, but several different diseases. Such a multitude of forms further complicates the diagnosis of this condition.
Primary form (tuberculous chancre) is most common in children, has an exogenous nature of infection. It is characterized by the development of reddish-brown papules on the skin approximately 3-5 weeks after the pathogen enters the tissues. Over time, the papule ulcerates, but remains the same painless. After the formation of a superficial ulcer, regional lymphadenitis occurs, which persists for about a month. Then comes the stage of resolution and healing, but complications in the form of disseminated skin tuberculosis or secondary infection are also possible.
Acute miliary skin tuberculosis – this form has an endogenous nature and occurs mainly in patients with severe forms of disseminated tuberculosis, in which the pathogen spreads through the body hematogenically. The symptoms of such a lesion are the development of symmetrical rashes on the trunk and limbs in the form of small reddish–brown nodules, vesicles, papules.
Tuberculous lupus is the most common form of skin tuberculosis. This type of lesion is characterized by the development of several tubercles (lupus) with a diameter of 2-3 millimeters, they are located in the dermis and are covered (in the absence of ulceration) by the epidermis. The favorite localization of formations is the face, the skin of the auricles, neck, but sometimes the trunk, as well as the mucous membranes of the mouth and nose can also be affected. Lupomas are painless, have a soft consistency, when pressed with a slide, they acquire a yellow color. Over time, they can resolve, leaving behind scar tissue or cause long-term non-healing ulcers. This type of skin tuberculosis has a long recurrent course with exacerbations in the cold season, in some cases, lupomas can fuse together, forming flat lesions.
Colliquative skin tuberculosis (scrofuloderma) – this form belongs to the endogenous types of the disease and mainly affects children with tuberculous lesions of the lymph nodes. The skin in the projection of the affected nodes (mainly the neck, lower jaw, armpits) first acquires a bluish hue, then several ulcers with an abundance of necrotic tissue form on its surface. As a rule, ulcers are painless, but after their healing they leave pronounced scars.
Warty form is an exogenous form of pathology, it mainly affects butchers, pathologists, veterinarians and other persons who have contact with infected material. The skin of the hands, hands and fingers is almost always affected. The disease begins with the formation of small rashes surrounded by an inflammatory border. Soon after, they begin to grow and merge with each other, forming one large lesion. The disease can last for many months, with the resolution of the focus, noticeable scars and scars are formed.
Miliary-ulcerative form is a rather rare form of pathology that occurs in severely weakened patients against the background of tuberculous lesions of the lungs, kidneys or intestines. At the same time, infection of the skin occurs when biological fluids (urine, saliva, sputum) containing a large number of mycobacteria get on it. For this reason, the areas of the skin surrounding the mouth, anus, and genitals are mainly affected. First, small red bumps develop, which quickly ulcerate, merge with each other and form continuous lesions.
Papulonecrotic skin tuberculosis is a form of the disease characterized by a highly developed allergic component and vasculitis, mainly affects adolescents. Its manifestations are the development of erythema on the extensor surfaces of the skin of the extremities and buttocks, after which a small ulcer appears in the center of redness. After its resolution, a clear scar with smooth edges remains.
Compacted form (Bazin’s erythema) – just as in the previous case, allergic processes and hypodermal vasculitis play a significant role in the pathogenesis of the disease. Mainly affects young girls, develops on the skin of the shins. It has the appearance of several deeply located nodes of dense consistency, with a diameter of 1-5 centimeters. Sometimes they can ulcerate, in addition, nodes often cause regional lymphadenitis.
In phthisiology, there are also many more rare forms of this disease – indurative, lichenoid and a number of others. But the vast majority of them are complications of tuberculous lesions of internal organs.
In modern dermatology, the diagnosis is a significant problem due to the large number of forms of the disease and, as a consequence, the variety of symptoms. To detect this pathology, a dermatological examination is used, the determination of antibodies to tuberculosis in the blood and the presence of mycobacteria in the foci of skin lesions. During the examination, attention is paid to the appearance of the patient, the nature of the rash, the duration of their development and other factors. However, even the presence of suspicious formations on the skin does not give complete confidence in the presence of skin tuberculosis.
Determination of the titer of antibodies to tuberculosis bacteria is a fast and effective diagnostic method, however, in some cases it can also give erroneous results. For example, a recent BCG vaccination can give false positive results, and false negative ones often occur in weakened patients or persons who have exogenous forms of skin tuberculosis. A much more reliable method is to determine the presence of mycobacteria in the separated ulcers or punctate from papules or tubercles. Today, the polymerase chain reaction (PCR) method is used for this, which makes it possible to identify even the smallest amounts of the pathogen DNA in the material under study in a matter of hours. In vitro tests for tuberculosis are also informative.
Skin tuberculosis therapy includes all standard measures and medications that are used for other forms of tuberculosis lesions. First of all, these are anti-tuberculosis drugs (isoniazid, rifampicin, PASC, kanamycin), the dosage of which is calculated by the doctor individually. To reduce the side effects of their use, calcium supplements, B vitamins, vitamin E and other supportive medications are additionally prescribed. Taking into account the fact that a decrease in the activity of immunity plays an important role in the development of skin tuberculosis, it is advisable to prescribe immunostimulating agents.
For the treatment of skin tuberculosis, physiotherapy measures are also used. Especially useful is the use of ultraviolet irradiation of the skin, which significantly accelerates the recovery of the patient and reduces the likelihood of complications. Among other methods of physiotherapy for skin tuberculosis, electrophoresis is often used. It is important in general to strengthen the body’s resistance to infection, which is achieved by proper or therapeutic nutrition, improving living conditions, getting rid of bad habits.
Prognosis and prevention
In the presence of skin tuberculosis of exogenous origin, the prognosis with proper treatment is usually favorable. Relapses can be observed only in case of violation of the treatment plan or (in rare cases) infection with a drug-resistant form of mycobacterium. In endogenous forms of the disease, the prognosis largely depends on the nature of the lesion of internal organs, the state of immunity, age and a number of other indicators.
Prevention of skin tuberculosis among persons at risk of contact with infected materials is reduced to the implementation of safety regulations (the use of gloves, glasses, masks). If there is a tuberculous lesion of the lungs or other internal organs, then the best prevention of skin lesions will be reasonable therapy of the underlying disease.