Erythema induratum is one of the forms of focal tuberculosis of the skin, which tends to disseminate the process, developing against the background of systemic damage to internal organs by Koch’s wand. The disease has a gender coloring, women of reproductive age are more likely to get sick. It is characterized by a rash of creeping flat nodular infiltrates up to 10 cm in diameter, localized mainly on the extremities. Erythema induratum is diagnosed taking into account anamnesis, histology data, tuberculin samples. Treatment is carried out with new-generation anti-tuberculosis drugs according to individual schemes per kilogram of the patient’s weight, simultaneously strengthening the body’s defenses.
Erythema induratum is a chronic inflammation of the skin of a tuberculous nature. It develops a second time in patients suffering from or who have had a tuberculosis infection. Erythema induratum is the most common type of skin tuberculosis. It has no age restrictions, seasonality, endemicity. Mycobactria itself – the causative agent of any form of tuberculosis – was discovered by R. Koch in 1882. It is polymorphic, can exist and infect the patient at different stages of its development (as a bacillus, thread, grain or filtering microbe), therefore it causes a large number of different skin lesions. Today, several types of mycobacteria are known: avian, bovine and human. Human-type mycobacteria are most often found in the foci of Bazin’s erythema.
Bazin gave the first description of indurative erythema in 1861, not yet knowing about the cause of the pathology. Nevertheless, Bazin’s clinical observations are relevant today, especially in terms of the assumption that the cause of the disease is circulatory disorders as a result of prolonged hypothermia of the legs and hands, “standing” work. In modern dermatology, they are considered as factors that provoke the onset of the disease. The relevance of indurative erythema is associated with the ubiquitous trend of increasing the incidence of tuberculosis.
The causative agent of the disease is Koch’s wand. Infection occurs exogenously-endogenously. Erythema induratum develops very difficult, like any other tuberculosis of the skin. This is due to the fact that the skin itself is an unsuitable environment for the life of the causative agent of tuberculosis. The protective, barrier functions of the dermis in this case are so effective that the primary element of tuberculosis of the skin in its classic version – tuberculous tubercle – is rarely formed. The main role in the development of the disease is played by failures in the systems regulating the vital activity of the body: immune, vascular, endocrine; violation of metabolic processes. Unfavorable background for the development of tuberculosis of the skin are difficult living conditions, harmful production, climate. An aggravating factor in the occurrence and development of erythema induratum can be infections, especially children’s, allergization of the body.
In order for an erythema induratum to form, a combination of circumstances is necessary: firstly, there should be a large number of mycobacteria in an active state on the skin, moreover, their virulence should repeatedly exceed the protective capabilities of T-lymphocytes of local immunity. Secondly, Mycobacteria should migrate hematogenically or via lymphatic pathways from the primary, already existing in some organ focus of “cold” sluggish inflammation associated with incomplete capture of mycobacteria by macrophages to the supposed site of the primary element. They cause allergization of the body, reduce its immunity. The combination of these factors gives rise to the appearance of indurative erythema. Thus, at the site of the introduction of the Koch wand into the skin, the primary response of the dermis is formed, which, in combination with the lesion of the lymph nodes, forms a primary tuberculosis complex. In fact, this process can be called vasculitis of the deep layers of the skin of tuberculous etiology.
Indurative erythema is a dense, flat, barely rising above the surface of the skin formation in the form of a node with fuzzy boundaries, reaching the size of a chicken egg, located in the deep layers of the dermis and subcutaneous fat. The nodes are painful to the touch, are located symmetrically on the skin of the extremities, extremely rarely on the mucous membranes of the mouth and nose. Dense strands are felt between individual nodes during palpation due to phlebitis. The skin above the nodes is not initially changed, over time it acquires a purple-red hue. There is a constant growth of the primary element, while flat infiltrates form along the periphery.
Depending on what the node is “filled with”, over time it spontaneously undergoes different involution. If lymphoid cells predominate in the node, then after a few weeks it regresses from the center, leaving hyper- or depigmentation in the form of a ring on the skin. If the node consists of exudative elements, then over time it begins to “melt” in its central part with the formation of ulcers, the outcome of which is a sinking scar. Aggravate the process of trauma and irrational local therapy. Erythema induratum has a chronic course with exacerbations in winter and autumn. Subjective sensations usually do not occur in patients, some note the phenomena of prodroma.
Patients with suspected indurative erythema are advised by a dermatologist and a phthisiologist. Diagnosis of the disease is based on anamnesis data, X-ray detection of the primary focus of infection, clinical symptoms and histological examination of the node punctate. Histologically, an epithelioid tubercle infiltrate with central curd necrosis is detected in subcutaneous adipose tissue, which is specific for all diseases of tuberculosis etiology. Typical for erythema induratum is secondary infiltrative vascular lesion.
With erythema induratum, the body in response to the introduction of Koch’s bacillus gives a strong immune response, so specific tuberculin tests are positive in 70% of cases, which is of great diagnostic importance. Three tests are considered to be the main ones: the subcutaneous Koch test, the subcutaneous Pirke test and the intradermal Mantoux test. The essence of the samples is the reaction of antigen (mycobacterium) – antibody (tuberculin serum). The result is evaluated by changes in the skin. Modern serological testing has the same basis. Bacterial examination is possible only at the late stages of the involution of Bazin’s erythema, during its decay, and therefore is not informative enough. Differentiate indurative erythema Bazin with spontaneous panniculitis, vulgar ecthyma, nodular erythema, scrofuloderma.
Treatment and prevention
The treatment of the disease is complex, has two directions: therapy of general tuberculosis and treatment of local, skin manifestations. The basis of therapy is anti-tuberculosis drugs. According to bacterial activity, I distinguish three groups of drugs: high (rifampicin), medium (streptomycin), moderate efficacy. They act on different parts of the vital activity of microbes (inhibit the growth, reproduction of mycobacteria, destroy their enzymatic, metabolic processes), therefore, the best effect of treatment is achieved with a combination of drugs of different groups. The result of treatment depends on the patient’s condition, therefore, general restorative therapy is indicated: good nutrition, a salt-free diet for the prevention of inflammation and allergies, antihistamines (clemastine), hyposensitizing drugs (astemizole), means that strengthen immunity (recombinant interferon gamma-1), correcting peripheral blood circulation (pentoxifylline), vitamin therapy (A, E, D2, riboflavin). Externally, UVI, fish oil preparations with natural antimicrobial activity, zinc-gelatin “boot” for a month are used.
Prevention consists in the correction of vascular diseases (varicose veins), ensuring normal working and living conditions. Sanatorium-resort treatment (seaside resorts) is shown. The prognosis with timely therapy and complete rehabilitation is favorable. An annual examination by a dermatologist and a phthisiologist is necessary.