What is the diagnostic workup and treatment for a patient suspected of having scrofuloderma?

Diagnostic Workup for Scrofuloderma

Obtain a deep tissue biopsy (punch or incisional) from the ulcer edge or sinus tract for both histopathology and mycobacterial culture, as this provides the highest diagnostic yield for confirming scrofuloderma. 1, 2, 3

Clinical Recognition and Initial Assessment

• Look for characteristic features: undermined ulcers with purulent discharge, sinus tracts overlying lymph nodes (especially cervical or supraclavicular), bone, or joints 1, 2, 4
• Document constitutional symptoms: low-grade fever, night sweats, weight loss, decreased appetite, and chronic cough lasting weeks to months 1
• Examine for underlying tuberculous foci: palpate for enlarged lymph nodes beneath skin lesions, assess for bone tenderness or joint swelling in affected areas 2, 5
• Measure and photograph lesions: document size, depth, presence of undermined edges, and extent of sinus tract formation 1, 5

Microbiological Diagnosis (Critical Step)

Multiple sampling methods are essential because single tests frequently miss the diagnosis:

• Tissue biopsy for culture: This is the gold standard—obtain deep tissue from the ulcer base or sinus tract wall and send for mycobacterial culture, as surface swabs are inadequate 2, 3
• Acid-fast bacilli (AFB) smear: Perform on discharge or tissue, though sensitivity is low (often negative even when culture is positive) 2, 5
• PCR/GeneXpert MTB/RIF: Run on tissue or aspirate, but recognize that PCR-negative, culture-positive cases occur, so negative PCR does not exclude scrofuloderma 1, 3
• Fine needle aspiration (FNA): Use for deeper collections or lymph nodes—this is less invasive and provides material for culture 3
• Repeat cultures if initial tests are negative: Given the high false-negative rate, perform serial cultures rather than relying on a single negative result 3

Histopathological Examination

• Request deep punch or incisional biopsy: Specimen must reach subcutaneous tissue to capture characteristic granulomatous inflammation 2, 5
• Expected findings: Epithelioid granulomas with or without caseating necrosis, though absence of classic features does not exclude tuberculosis 2
• Rule out malignancy: Chronic non-healing ulcers with undermined edges can mimic squamous cell carcinoma or other malignancies, making histopathology essential 5

Imaging Studies

• X-ray of affected area: Obtain plain films of underlying bone if osteomyelitis is suspected (look for periosteal reaction, lytic lesions, or chronic osteomyelitis features) 2
• MRI of affected region: Use when deep tissue involvement is suspected—MRI can delineate extension from lymph nodes to skin and identify underlying bone or joint involvement 4
• Chest X-ray and CT chest: Mandatory to screen for pulmonary tuberculosis, though scrofuloderma can occur without active lung disease 1, 4

Screening for Disseminated Tuberculosis

Always investigate for coexisting tuberculosis at other sites, as scrofuloderma frequently accompanies systemic disease:

• CNS evaluation: If headache, altered mental status, or neurological symptoms are present, obtain lumbar puncture and brain CT/MRI to rule out tuberculous meningitis or tuberculoma 1
• Abdominal imaging: Consider if abdominal symptoms suggest peritoneal or gastrointestinal tuberculosis 1
• Baseline laboratory tests: Complete blood count, ESR, CRP, liver and renal function (needed before starting antitubercular therapy) 1

Common Diagnostic Pitfalls

• Treating empirically for bacterial infection: Pseudomonas or other bacteria may be co-isolated, leading to quinolone therapy that partially improves symptoms but delays tuberculosis diagnosis 3
• Relying on single negative PCR: PCR-negative, culture-positive cases are well-documented—always send cultures even if molecular tests are negative 3
• Superficial sampling: Surface swabs or shallow biopsies miss the diagnosis—deep tissue is required 2, 3
• Assuming isolated disease: Failure to screen for pulmonary, CNS, or disseminated tuberculosis can result in incomplete treatment 1

Treatment Initiation

• Standard four-drug regimen: Rifampicin, isoniazid, pyrazinamide, and ethambutol for 2 months (intensive phase), followed by rifampicin and isoniazid for 4 months (continuation phase) 1
• Add pyridoxine: 25-50 mg daily to prevent isoniazid-induced peripheral neuropathy 1
• Consider corticosteroids: Prednisolone may be added if CNS involvement (meningitis or tuberculoma) is present 1
• Wound care: Apply non-adherent dressings, irrigate with sterile saline, and change dressings every 5-7 days as lesions heal 1
• Monitor for drug resistance: If culture grows Mycobacterium tuberculosis, request drug susceptibility testing to guide therapy adjustments 1, 2