Cutaneous tuberculosis
Cutaneous TB; lupus vulgaris; scrofuloderma; TB verrucosa cutis; tuberculides
Cutaneous tuberculosis is uncommon in the UK but increasing with migration, immunosuppression and HIV. Clinical phenotypes — lupus vulgaris (reddish-brown plaque with apple-jelly nodules on diascopy), scrofuloderma (subcutaneous TB extending to skin from underlying nodes or bone), TB verrucosa cutis (warty plaque from exogenous inoculation), orificial TB (mucosal ulceration in advanced visceral disease), miliary TB (cutaneous papules in disseminated disease), and the immunological tuberculides (lichen scrofulosorum, papulonecrotic tuberculide, erythema induratum of Bazin). Lupus vulgaris is the commonest in temperate climates and carries a recognised cumulative risk of cutaneous SCC within chronic plaques after decades — a Marjolin-like scenario.
Clinical variants
- Lupus vulgaris — commonest in temperate climates. Slow-growing reddish-brown plaque, often on face or neck; apple-jelly nodules on diascopy (compressed pressure transluminates a yellow-brown granulomatous infiltrate). Atrophic scarring at the centre; progressive over years.
- Scrofuloderma — TB of subcutaneous tissue / nodes / bone extending to skin; bluish-red nodule that breaks down to a sinus tract with stringy purulent discharge; classical sites — neck, axilla, groin.
- TB verrucosa cutis — warty hyperkeratotic plaque from exogenous inoculation (pathologists, butchers, farmers); usually on hands.
- Orificial TB — ulceration around mouth, anus, genitalia in patients with advanced visceral TB.
- Miliary TB — disseminated tiny papules in profoundly immunosuppressed.
- Tuberculides — hypersensitivity reactions in TB-sensitised individuals: lichen scrofulosorum, papulonecrotic tuberculide, erythema induratum of Bazin.
Marjolin-like malignancy risk
- Chronic lupus vulgaris carries an established risk of cutaneous SCC arising within long-standing plaques after decades — analogous to Marjolin ulcer in chronic scars / burns.
- Suspicion for malignancy is raised by an enlarging or ulcerating area within a stable plaque, sudden change in symptomatology or refractoriness to TB treatment.
- Biopsy any new component; cSCC in lupus vulgaris is biologically aggressive.
Diagnosis
- Biopsy — granulomatous inflammation with caseation in classical lupus vulgaris and scrofuloderma; AFB stain (Ziehl-Neelsen) positive in 30–50%; tuberculides typically AFB-negative.
- Microbiology — TB PCR, mycobacterial culture (4–8 weeks).
- Tuberculin skin test (Mantoux) and interferon-gamma release assay (IGRA — QuantiFERON, T-SPOT.TB).
- Workup for systemic TB — chest X-ray, sputum culture if symptomatic, urinalysis, fundoscopy for ocular TB.
- HIV testing in all confirmed TB.
Management
- Standard quadruple anti-TB therapy — rifampicin + isoniazid + pyrazinamide + ethambutol for 2 months, then rifampicin + isoniazid for 4 months (RIPE then RH).
- Drug-resistant disease — extended regimens per regional MDR-TB protocol.
- Multidisciplinary input — TB / infectious diseases service; dermatology for skin assessment; surgical input for scrofuloderma.
- Co-existing or HIV-positive — initiate antiretroviral therapy concurrently; immune-reconstitution inflammatory syndrome (IRIS) may worsen skin lesions transiently.
- Notify per local public-health protocol; contact tracing.
- Long-term surveillance for SCC within chronic lupus vulgaris plaques.
References
- WHO Guidelines for the management of tuberculosis, 2022.
- NICE NG33. Tuberculosis. London: NICE; 2016 (last updated 16 February 2024).
- Barbagallo J et al. Cutaneous tuberculosis — diagnosis and treatment. Am J Clin Dermatol; 2002.
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