What Is Skin Tuberculosis (TB)?
Laennec first documented skin TB in 1826. Since the lesions were usually found in people who performed dissections or autopsies, these were initially called prosector’s warts. Skin or cutaneous tuberculosis was one of the major public health concerns in the nineteenth and twentieth centuries. But with the improved hygiene habits among the general population, utilization of the BCG vaccine, and beneficial chemotherapy, there has been a marked decrease in skin tuberculosis cases. However, with the beginning of diseases such as human immunodeficiency virus (HIV), drug-resistant tuberculosis cases, and the increase in immune-suppressing treatments, skin tuberculosis has resent since the mid-1990s. Common pathological types of cutaneous TB are miliary tuberculosis, lupus vulgaris, verrucosa cutis, and scrofuloderma.
What Causes Skin Tuberculosis?
Mycobacterium tuberculosis, a tubercle bacillus, is the primary etiologic agent for skin tuberculosis. Sometimes, it is also caused by Mycobacterium Bovis or Bacillus Calmette- Guerin (BCG). Skin tuberculosis occurs after direct inoculation of the bacteria into the skin. It can also happen by the hematogenous route, i.e., by spreading the bacteria into the skin via the bloodstream. The body's immune response to the tubercle bacillus influences the symptoms of the infection. The previous infection with the mycobacterium bacteria results in moderate to high immunity. Drug-induced immunosuppression, tumor necrosis factor (TNF) - alpha inhibitors, human immunodeficiency virus (HIV), acquired immunodeficiency syndrome (AIDS), or leukemia may reactivate latent TB.
What Are the Risk Factors of Skin Tuberculosis?
Skin tuberculosis can occur in people of all ages. Still, several risk factors affect the occurrence of skin tuberculosis:
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Skin tuberculosis can be exogenous (infection resulting from direct inoculation of tubercle bacilli into the skin of the susceptible person) or endogenous (infection caused by an infectious agent already present in the body), depending upon the route of infection.
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Due to prolonged exposure or inappropriate administration, the multi-drug resistant (MDR) bacterial strains are resistant to drugs like Isoniazid and Rifampicin.
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Children due to their immature immune systems.
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People with weakened systems include HIV or AIDS, malnutrition, smoking, alcoholism, silicosis, diabetes mellitus, and gastrectomy.
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Close contact with people who already had TB.
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Visiting or living in a country or community where TB is common.
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Overcrowded living conditions.
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Health care workers.
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Malnutrition, excessive alcohol intake, and poverty promote the spread of the disease.
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Individuals with a stronger immune system can easily cope with mycobacterium infections.
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There is a geographical variation, with the prevalence of different clinical forms of skin tuberculosis in distinct locations.
What Are the Clinical Features of Skin Tuberculosis?
The clinical features of cutaneous TB vary based on the type of skin infection:
Tuberculosis Verrucosa Cutis
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Purplish or brownish-red warty growth.
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Lesions appear on knees, elbows, hands, feet, and buttocks.
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If left untreated, lesions persist for years but may resolve without treatment.
Lupus Vulgaris
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A chronic and progressive form of skin tuberculosis.
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Small, well-defined reddish-brown papules merge into plaques with a gelatinous consistency (apple-jelly nodules).
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Lesions persist for years, leading to esthetic alterations and skin cancer.
Scrofuloderma or Tuberculosis Colliquativa Cutis
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Firm, painless, cold abscesses spontaneously with purple-ulcerated plaques
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Lesions may later be involuted, creating keloid scars.
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The main sites are lymph nodes, bones, joints, or testicles.
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Heal without treatment, but it may take years.
Miliary Tuberculosis
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Small reddish-white or reddish-purplish spots become necrotic, later developing into ulcers and abscesses.
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Develops in people with impaired cellular immunity and children.
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The prognosis is poor.
Orificial Tuberculosis or Tuberculosis Cutis Orificialis
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Affects middle-aged or older adults with an advanced form of tuberculosis.
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Lesions are reddish-yellowish and painful, which develop into ulcers.
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The prognosis is poor since it is associated with advanced internal disease.
Tuberculous Chancre
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A rare form of skin tuberculosis is found mainly in children living in areas of low immunization coverage.
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Lesions are firm, painless, slow-growing nodules or papules which may develop into ulcers.
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Lesions may heal between three to twelve months, leaving scars and calcifications in regional lymph nodes.
How Is Skin Tuberculosis Diagnosed?
Skin tuberculosis diagnosis is generally based on characteristic clinical features on skin biopsy and the individual's medical history. Additionally, the following tests may be necessary:
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Tuberculin skin test (Mantoux or PPD test).
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Special stains such as Ziehl-Nielsen and polymerase chain reaction (PCR) detect tubercle bacilli in the skin.
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Sputum culture.
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Interferon-gamma release assay (IGRA) blood test like quantiFERON-tuberculosis gold.
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Chest X-Rays – To detect pulmonary tuberculosis infection.
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Computed tomography (CT) scans.
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Bone scans.
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Blood, sputum, and urine culture samples
What Is the Treatment of Cutaneous Tuberculosis?
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The standard treatment regimen for individuals with pulmonary or extrapulmonary tuberculosis involves four drugs- Isoniazid, Rifampicin, Pyrazinamide, and Ethambutol for eight weeks.
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Individuals with latent TB infection but no active TB may also be treated with anti-tuberculosis medications to prevent the development of active disease.
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In a few cases, surgical excision is recommended in cases where drug therapy fails to cure skin TB.
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Plastic surgical reconstruction may help people disfigured by lupus vulgaris.
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Single drug therapy is not recommended.
How to Prevent Skin Tuberculosis?
The following measures may prevent skin tuberculosis:
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Using sterilized needles for injections.
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Early identification and proper treatment of infected individuals to prevent spread by contact.
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Having good nutrition.
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Consuming boiled and pasteurized milk.
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Practicing good hygiene habits.
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BCG vaccine helps prevent the spread of pulmonary TB.
What Is the Outcome of Cutaneous Tuberculosis?
Most forms of skin tuberculosis, such as scrofuloderma and tuberculosis verrucosa cutis, heal spontaneously. However, other forms like lupus vulgaris, tuberculosis verrucosa cutis, and scrofuloderma can become fatal if left untreated. In addition, some presentations of cutaneous tuberculosis, including miliary tuberculosis, imply significant systemic disease, which may be lethal. Treatment is usually successful with a course of appropriate multi-drug therapy, although some skin lesions are slow-healing.
Conclusion
Skin tuberculosis was one of the biggest causes of concern in public health issues globally. Skin tuberculosis can occur in individuals of all ages. However, several risk factors affect the occurrence of this condition. Skin tuberculosis is both preventable and treatable. Treatment is often successful with a course of appropriate multi-drug therapy, although some skin lesions heal slowly. Factors like good hygiene habits, better nutrition, and prompt treatment of tuberculosis have helped prevent the occurrence of skin tuberculosis.
