What does 'tuberculosis verrucous' refer to and what is the appropriate diagnostic work‑up and treatment regimen?

Tuberculosis Verrucosa Cutis: Diagnosis and Treatment

What is Tuberculosis Verrucosa Cutis?

Tuberculosis verrucosa cutis (TBVC) is a rare paucibacillary form of cutaneous tuberculosis caused by direct inoculation of Mycobacterium tuberculosis into the skin of a previously sensitized individual with moderate to high immunity. 1, 2 This represents only 1-2% of all tuberculosis cases and typically presents as warty, hyperkeratotic plaques on exposed areas such as hands, knees, ankles, and buttocks. 1, 2, 3

Diagnostic Work-Up

Clinical Evaluation

• Look for well-defined verrucous or warty plaques with inflammatory borders, most commonly on hands, knees, ankles, and buttocks, though atypical presentations including diffuse plantar keratoderma, sporotrichoid patterns, and keloid-like plaques have been reported. 2, 3, 4
• Obtain a detailed occupational and exposure history, as TBVC is often seen in farmers, healthcare workers, and laboratory personnel with prior TB sensitization. 1
• Assess for evidence of pulmonary or systemic tuberculosis, as some patients may have concurrent active TB at other sites. 4

Laboratory and Pathological Confirmation

• Perform skin biopsy for histopathological examination, which is essential for diagnosis given the paucibacillary nature of lesions. 1, 2, 5
• Obtain smears for acid-fast bacilli (AFB) from any discharge or lesional material, though these may be negative due to low bacterial load. 4
• Send tissue specimens for mycobacterial culture on Lowenstein-Jensen medium to confirm M. tuberculosis growth. 4
• Use PCR testing for M. tuberculosis identification when available, as this can provide rapid confirmation. 1
• Perform chest radiography to exclude pulmonary tuberculosis in all patients with suspected cutaneous TB. 6

Important Diagnostic Pitfall

Due to the paucibacillary characteristic of TBVC lesions, patients are frequently misdiagnosed, leading to chronification of skin infection for years or even decades. 1 One reported case went undiagnosed for 15 years before correct identification. 1

Treatment Regimen

Standard Treatment Protocol

Treat TBVC with the standard 6-month anti-tuberculosis regimen: 2 months of isoniazid, rifampin, pyrazinamide, and ethambutol (2HRZE), followed by 4 months of isoniazid and rifampin (4HR). 7, 8, 9, 1, 5

Initial Phase (First 2 Months)

• Isoniazid: 5 mg/kg daily (maximum 300 mg) 7, 9
• Rifampin: 10 mg/kg daily (maximum 600 mg) 7, 9
• Pyrazinamide: 35 mg/kg daily for patients <50 kg; 2.0 g daily for patients ≥50 kg 7, 9
• Ethambutol: 15 mg/kg daily 7, 9

Continuation Phase (Next 4 Months)

• Isoniazid: 5 mg/kg daily (maximum 300 mg) 7, 9
• Rifampin: 10 mg/kg daily (maximum 600 mg) 7, 9

Critical Management Principles

• Implement Directly Observed Therapy (DOT) as the standard of care to ensure adherence and prevent treatment failure. 7, 8, 9
• Perform drug susceptibility testing on all initial isolates and modify the regimen appropriately once results are available. 7, 9
• Never add a single drug to a failing regimen, as this leads to further drug resistance. 7, 8
• Monitor liver function tests every 2-4 weeks during treatment and assess for clinical signs of hepatotoxicity (nausea, vomiting, jaundice). 6

Expected Clinical Response

Patients treated with standard anti-tuberculosis drugs show subsequent improvement of skin lesions, though some cases with extensive disease may require surgical intervention in addition to medical therapy for complete resolution. 1, 5, 4

Special Consideration for Refractory Cases

In rare instances where lesions persist despite appropriate anti-tubercular therapy, surgical excision may be necessary as adjunctive treatment to achieve complete resolution. 4