Cutaneous Tuberculosis: Understanding the Skin-Related Forms of TB

Tuberculosis (TB) is a long-standing infectious disease primarily known for affecting the lungs. However, TB is not limited to the respiratory system. In some cases, it can involve other organs, including the skin, leading to a condition known as cutaneous tuberculosis (CTB).

Although rare, skin tuberculosis is clinically important because it often resembles other dermatological diseases, making diagnosis challenging. Early recognition and correct treatment are essential to prevent complications and long-term skin damage, especially in regions where TB is common.

What Is Cutaneous Tuberculosis?

Cutaneous tuberculosis refers to tuberculosis infection involving the skin and subcutaneous tissues. It is mainly caused by Mycobacterium tuberculosis and, less commonly, Mycobacterium bovis. The infection can develop when TB bacteria directly enter the skin or spread from an existing infection elsewhere in the body.

CTB accounts for a small percentage of extrapulmonary TB cases, but its varied presentation makes it a significant diagnostic concern for clinicians.

Is Skin Tuberculosis Contagious?

Skin tuberculosis is not highly contagious. Transmission through direct skin contact is extremely uncommon. Most cases occur due to:

• Spread of TB bacteria from internal organs

• Reactivation of dormant TB bacteria

• Self-inoculation in individuals already infected with TB

How Does Cutaneous Tuberculosis Develop?

There are several recognized pathways through which TB can involve the skin:

1. Direct Inoculation

TB bacteria enter the skin through cuts, wounds, or abrasions.

2. Bloodstream Spread

Bacteria travel via the blood from a distant infected organ to the skin.

3. Contiguous Extension

The infection spreads directly from nearby infected structures such as lymph nodes, bones, or joints.

4. Reactivation of Dormant TB

Previously inactive TB bacteria become active within the skin.

Who Is at Higher Risk?

Certain individuals are more vulnerable to developing cutaneous TB, including those with:

• Weakened immune systems (HIV, organ transplant recipients, long-term steroid use)

• Poor nutritional status

• Overcrowded or unhygienic living conditions

• Close contact with individuals having active TB

• Extremes of age (children and elderly)

• In some studies, females appear to have a slightly higher risk

Different Types of Cutaneous Tuberculosis

CTB presents in several forms, each with distinct clinical features:

Primary Cutaneous Tuberculosis

Occurs in individuals with no prior TB exposure. It typically starts as a painless skin lesion that later involves nearby lymph nodes.

Lupus Vulgaris

The most frequently observed form. It appears as slowly enlarging reddish-brown plaques, commonly affecting the face, neck, and limbs.

Scrofuloderma

Develops when TB spreads from underlying lymph nodes or bones to the skin, forming ulcers with persistent discharge.

Tuberculosis Verrucosa Cutis

Seen in individuals with previous TB exposure, such as healthcare workers or farmers. It causes thick, warty lesions, usually on hands or feet.

Orificial Tuberculosis

A rare but severe form involving mucosal areas like the mouth, anus, or genital region, often associated with advanced internal TB.

Acute Miliary Cutaneous Tuberculosis

Results from widespread bloodborne TB spread, producing numerous small lesions across the skin.

Rare Hypersensitivity-Related Forms

Some skin manifestations are immune reactions rather than direct bacterial infection:

• Papulonecrotic Tuberculid – necrotic papules due to immune response

• Lichen Scrofulosorum – grouped tiny papules, mainly in children

• Erythema Induratum of Bazin – painful nodules on the legs linked to TB sensitivity

Common Signs and Symptoms

Skin Findings

• Nodules, plaques, ulcers, or wart-like growths

• Scarring and pigment changes during healing

Common Locations

• Face, neck, arms, legs, and areas near lymph nodes

Associated Symptoms

• Pain, swelling, discharge

• Fever, weight loss, night sweats

• Cough if systemic TB is present

How Is Cutaneous Tuberculosis Diagnosed?

Diagnosing CTB requires a combination of clinical suspicion and laboratory confirmation.

Clinical Evaluation

• Detailed medical history

• Assessment of TB exposure and risk factors

Laboratory Investigations

• Skin biopsy showing granulomatous inflammation

• TB culture or PCR testing

• Ziehl–Neelsen staining for acid-fast bacilli

Imaging Studies

• Used when deeper tissues, bones, or lymph nodes are suspected to be involved

Conditions That Can Mimic Cutaneous TB

CTB can resemble several infectious and non-infectious skin diseases, including:

• Leprosy – characterized by numb skin patches and nerve involvement

• Deep Fungal Infections – identified through fungal cultures

• Sarcoidosis – granulomas without tissue necrosis

• Psoriasis – silvery, well-defined plaques

• Leishmaniasis – diagnosed by detecting parasites

• Discoid Lupus Erythematosus – confirmed by autoimmune markers

• Atypical Mycobacterial Infections – caused by non-tuberculous mycobacteria

Accurate diagnosis is crucial to avoid inappropriate treatment.

Treatment of Cutaneous Tuberculosis

Standard Anti-Tubercular Therapy (ATT)

Treatment follows WHO guidelines and is similar to pulmonary TB management.

Shorter 4-Month Regimen (Eligible Patients)

• Intensive Phase (2 months): Isoniazid, Rifapentine, Pyrazinamide, Moxifloxacin

• Continuation Phase (2 months): Isoniazid, Rifapentine, Moxifloxacin

Conventional 6-Month Regimen

• Intensive Phase (2 months): Isoniazid, Rifampicin, Pyrazinamide, Ethambutol

• Continuation Phase (4 months): Isoniazid and Rifampicin

Treatment duration may be extended depending on disease severity or response.

Management of Drug-Resistant Cases

When standard therapy fails due to drug resistance, second-line medications are required under specialist supervision.

Modern WHO-recommended regimens now focus on all-oral combinations, including:

• Bedaquiline

• Pretomanid

• Linezolid

• Moxifloxacin (if sensitive)

Longer oral regimens may be used if shorter options are unsuitable.

Role of Surgery

Surgical intervention is supportive and may include:

• Drainage of abscesses

• Removal of necrotic tissue

• Reconstruction or skin grafting for cosmetic correction

Surgery is always performed after adequate ATT to reduce recurrence risk.

Complications and Outlook

With timely treatment, outcomes are generally excellent. However, delayed or untreated CTB may result in:

• Permanent scarring and pigmentation

• Rare malignant transformation

• Disease spread in immunocompromised individuals

Prevention and Public Awareness

Preventive strategies align with general TB control measures:

• Early diagnosis and treatment of TB

• Good hygiene and wound care

• Nutritional support

• Public health education

• BCG vaccination in endemic regions

Key Takeaway

Cutaneous tuberculosis is an uncommon but important form of TB that affects the skin. Because it often resembles other skin conditions, a high level of clinical awareness is necessary. With early diagnosis and appropriate treatment, most patients recover fully with minimal long-term effects.