Lichenoid tuberculid is one of the dermatological forms of this infectious disease, most often occurring as a complication of tuberculosis of other types and localizations against the background of reduced immunity. Symptoms are small symmetrical nodules of pink or brown color, located on the trunk and covered with whitish scales. The diagnosis is made on the basis of the results of an examination by a dermatologist or phthisiologist and tuberculin samples, in suspicious cases, a biopsy and histological examination of the affected tissues are performed. The disease is treated with traditional anti-tuberculosis drugs, immunostimulating and vitamin therapy is prescribed.
A18.4 Tuberculosis of the skin and subcutaneous tissue
Lichenoid tuberculid, or scrofulous lichen is a form of tuberculous lesion of the skin, which most often develops in children with reduced immunity. In some cases, the disease occurs in adults suffering from severe immunodeficiency. Lichenoid tuberculid is a rather rare type of this infectious disease. The dynamics of skin manifestations depends on the course of tuberculosis processes in the body as a whole. For example, with successful treatment of tuberculosis of the lungs or other organs, dermatological symptoms also disappear, relapses after recovery are very rare. Lichenoid tuberculid is considered one of the most benign forms of skin lesions with mycobacteria.
This condition often occurs as a complication of other dermatological forms of tuberculosis, such as tuberculous lupus, scrofuloderma and papulo-necrotic tuberculosis. It is also possible to develop lichenoid tuberculid due to the active involvement of mycobacteria in the lungs, lymph nodes and bone system. A number of phthisiologists and dermatologists believe that a significant role in the occurrence of this condition is played not by the colonization of the skin by the pathogen itself, but by a kind of allergic reaction to its vital activity in the body. This fact is confirmed by documented cases of lichenoid tuberculid against the background of active treatment of tuberculous lupus. During therapy, a huge number of mycobacteria die, elements of their cells enter the bloodstream, provoking the development of allergic reactions.
Indirect confirmation of the allergic nature of lichenoid tuberculid are observations indicating the presence of a constitutional predisposition to this disease. Patients with a history of various allergic conditions are often noted – from simple urticaria to bronchial asthma. All this gives researchers reason to believe that lichenoid tuberculid is not a separate form of infection with mycobacteria, but only a rare symptom of other forms of the tuberculosis process. Nevertheless, to date, in the official classification, this disease is allocated to a separate type.
Lichenoid tuberculid is accompanied by papular rashes and nodules, which are usually located on the skin of the trunk symmetrically with respect to the median line of the body. Occasionally, skin manifestations develop on the upper extremities, neck, face, buttocks and shins. Papular elements are often associated with hair follicles. The size of nodules in lichenoid tuberculid ranges from 1 to 3 millimeters, their color varies from pink to brown. Nodular elements often merge with each other with the formation of plaques of various sizes and shapes. Whitish (rarely brown) scales are formed on their surface.
Any other symptoms in this dermatological condition are almost never observed. Occasionally, patients with lichenoid tuberculid complain of a slight itching or burning sensation on the affected areas of the skin. Rashes persist for one and a half to two months, after which they spontaneously resolve, leaving behind superficial inconspicuous scars, areas of hypopigmentation or skin atrophy. If the tuberculous process persists in the body, then after the nodules are resolved, a relapse of lichenoid tuberculid is possible, while the seasonality of the disease can be noticed – especially often new rashes appear in the autumn-winter period.
The determination of lichenoid tuberculid in dermatology is based on the examination of the patient, the study of the anamnesis and the results of the Mantoux test and the diaskin test. When carrying out a differential diagnosis, in controversial cases, skin biopsy and histological examination of nodular element tissues, enzyme immunoassays (quantiferon test for tuberculosis, t-spot.tb) can be performed.
On examination, characteristic symmetrical rashes on the trunk or other parts of the body, nodules 1-3 millimeters in size and plaques resulting from their fusion are revealed. Sometimes, against the background of rashes with lichenoid tuberculid, light spots and scars remaining from previous healed nodules are determined.
In the anamnesis or medical history of the patient, an active tuberculosis process is necessarily detected: damage to the lungs, lymph nodes, skin (scrofuloderma, papulonecrotic tuberculosis). Almost always, patients with lichenoid tuberculid have signs of decreased immunity: an increased frequency of colds, exacerbation of chronic infectious pathologies, fungal lesions of the skin and internal organs. Allergic tests for sensitivity to tuberculin are always sharply enhanced, concomitant diseases of an allergic nature (urticaria, bronchial asthma) can be determined.
In the process of histological examination of the skin with lichenoid tuberculosis, moderate lymphocytic and histiocytic infiltration of the dermis with predominant localization around hair follicles or sweat glands is detected. Sometimes the infiltration takes the form of epithelioid cell granulomas, while there are no areas of caseous necrosis in their center. Mycobacteria in the dermis with lichenoid tuberculid is rarely detected, which serves as additional evidence of the allergic nature of the disease. Differential diagnosis should be made with syphilitic skin manifestations and some forms of lichen planus.
An essential role in the treatment of lichenoid tuberculid is played by the treatment of the main tuberculosis process, which can be localized in the lymph nodes or internal organs. For this purpose, traditional anti-tuberculosis drugs are used. As a rule, after a successful cure of tuberculosis, skin manifestations quickly disappear and no longer appear. With lichenoid tuberculid, it is also important to pay attention to the immunological status of the patient, since this disease occurs against the background of weakening of the body’s defenses. To normalize immunity, immunostimulating drugs of synthetic or plant origin are used.
To strengthen the body’s resistance to tuberculosis, vitamin and mineral complexes, a special diet with a low salt content and a high amount of proteins are used. With lichenoid tuberculid, physiotherapy procedures (ultraviolet irradiation) and sunbathing are also indicated. Spa treatment in the treatment of this condition is as important as in other forms of tuberculosis. With itching of the skin, corticosteroid ointments are prescribed locally to reduce the severity of the symptom.
Prognosis and prevention
The prognosis of lichenoid tuberculid is almost always favorable, however, it is influenced by the course and form of the main tuberculosis lesion. Rashes and nodules are prone to spontaneous resolution 1-2 months after their occurrence, in their place there are only barely noticeable scars or slight hypopigmentation. To prevent lichenoid tuberculid, it is necessary to detect and treat tuberculosis infection of the body in a timely manner, and in the presence of a tuberculosis process, monitor the level of immunity. These measures not only prevent the development of skin lesions, but also contribute to the speedy full recovery of the patient.