Lupus vulgaris is a painful nodular skin condition most commonly caused by the microorganism mycobacterium tuberculosis. It usually affects the face, or the buttocks and trunk. The term “lupus” is used to refer to the skin ulceration and necrosis that occurs when it is left untreated. Lupus vulgaris is also known as tuberculosis luposa cutis or tuberculosis cutis luposa because of its etiologic agent. Like any other form of tuberculosis, it is treatable with the four-drug combination of isoniazid, rifampicin, ethambutol, and pyrazinamide.
Mycobacterium tuberculosis preferably stays and thrives in the lung tissues, causing pulmonary tuberculosis (TB). When TB occurs in other organs and tissues, it is labeled extrapulmonary TB. Different forms of extrapulmonary TB exist, including miliary tuberculosis, scrofula, TB verrucosa cutis, tuberculids, metastatic tuberculous abscesses, and metastatic tuberculous ulceration, or tuberculous gumma. These, along with lupus vulgaris, may present as cutaneous conditions that are caused by TB infection.
Relatively uncommon, lupus vulgaris is a variant of cutaneous TB that is persistent and progressive. The initial lesions are small and sharply defined nodules, with a reddish-brown hue and a gelatinous consistency. These lesions are also known as apple jelly nodules. Persistence of these lesions leads to coalescence and tissue destruction. There is no age group exempt from lupus vulgaris, but most patients go to the doctor before the age of 30 with these symptoms.
Among Caucasians, the head and neck region is typically affected. In Asians, lupus vulgaris more commonly occurs on the buttocks and extremities. Some cases of penis involvement have also been reported.
The causative organism reaches the skin through various routes. One route is direct inoculation, wherein the organism spreads to the dermis after entering an open skin wound. The hematogenous, or blood, route and the lymphatic route may be utilized when the organism is transferred to the skin from an affected internal organ. Another route is direct extension, either from infected joints or glands beneath the skin.
Diagnosis of lupus vulgaris is confirmed through a skin biopsy of the affected area. Histopathological results would state the presence of caseating epithelioid granulomas that contain acid-fast bacilli. To exclude coexisting pulmonary TB infection, a sputum culture or a chest X-ray may be requested. A Mantoux tuberculin skin test and other radiological examinations may also be performed.
The most effective treatment of lupus vulgaris is the oral intake of antitubercular drugs. Other antibiotics may also be given to treat any secondary bacterial infections. Treatment with these drugs lasts months or years, depending on the severity of the disease. When the face is severely disfigured or large areas of the skin are necrotic, surgical excision of the affected areas may be recommended.