What skin lesions are associated with active tuberculosis (TB)?

Skin Lesions Associated with Active Tuberculosis

The most common skin lesions associated with active tuberculosis are lupus vulgaris and scrofuloderma, which represent different manifestations of cutaneous tuberculosis. 1, 2, 3

Primary Types of Cutaneous TB Lesions

Lupus Vulgaris

• Most common form of cutaneous TB in many regions 3
• Clinical presentation:
  • Slowly progressive, well-defined erythematous scaly plaques
  • Various forms including plaque, ulcerative, hypertrophic, vegetative, papular, and nodular forms
  • Characteristic "apple jelly" appearance when pressed with a glass slide
  • Commonly affects face but can appear on other body parts
  • May lead to significant scarring if untreated 1, 2
• Histopathology: Granulomatous infiltration without caseation necrosis in the dermis 1

Scrofuloderma

• Results from contiguous spread of TB from underlying structures (usually lymph nodes)
• Clinical presentation:
  • Firm subcutaneous nodules that eventually suppurate and form ulcers or sinus tracts
  • Commonly affects cervical lymph nodes and chest area
  • Often leaves puckered scars after healing 2, 4

Other Cutaneous TB Manifestations

Papulonecrotic Tuberculid

• Represents a hypersensitivity reaction to mycobacterial antigens
• Presents as symmetrically distributed papuloulcerative lesions
• Usually occurs in patients with high tuberculin sensitivity 5

Lichen Scrofulosorum

• Characterized by small, skin-colored or slightly erythematous papules
• Often occurs in children and young adults with underlying TB
• Represents a tuberculid reaction pattern 3

Diagnostic Considerations

• Tuberculin skin test (PPD) is typically strongly positive in patients with cutaneous TB
  • Reactions >20mm are common in active cutaneous TB 3
• Histopathological examination is crucial for diagnosis
  • Shows granulomatous inflammation with or without caseation
  • Acid-fast bacilli are rarely seen in lupus vulgaris 5
• PCR testing for Mycobacterium tuberculosis DNA can be helpful for definitive diagnosis 5, 4
• Always consider underlying pulmonary or disseminated TB when cutaneous lesions are identified

Clinical Pearls and Pitfalls

• Cutaneous TB represents only 1-2% of extrapulmonary TB cases but should be considered in chronic, non-healing skin lesions 3
• Multiple forms of cutaneous TB can coexist in the same patient (e.g., lupus vulgaris with scrofuloderma) 4
• Cutaneous TB lesions respond well to standard anti-tuberculous therapy, but may leave significant scarring 1
• Failure to recognize and treat cutaneous TB can lead to extensive tissue destruction and disfigurement
• Always evaluate for systemic TB involvement when cutaneous TB is diagnosed

Treatment Approach

• Standard anti-tuberculous therapy is effective for cutaneous TB:
  • Initial phase: Four-drug regimen with isoniazid, rifampin, pyrazinamide, and ethambutol for 2 months
  • Continuation phase: Dual therapy with isoniazid and rifampin for 4-6 months
  • Significant clinical improvement is typically seen within 4 months 1
• Surgical intervention may be necessary for draining cold abscesses associated with scrofuloderma 2

Early recognition and prompt treatment of cutaneous TB lesions are essential to prevent complications and reduce transmission of tuberculosis.