A 56-year-old Bangladeshi male, presented with high grade fever and nodular skin lesions for 3 months. The skin lesions first appeared in the thigh followed by involvement of the trunk. Some of the lesions grew larger and ulcerated over time, releasing pus. He received several courses of antibiotics on suspicion of bacterial abscess without any significant improvement. His co-morbidities include hypertension, ischemic heart disease and chronic kidney disease secondary to long standing hypertension. He has been suffering from inflammatory oligoarthritis involving both knee joints and back for the last 2 years, which was labeled as undifferentiated spondyloarthritis. He took a number of NSAIDs and oral corticosteroids (prednislolone 20 mg daily) irregularly for pain relief. Intra-articular steroid injection was given on one occasion six months back. He had lost about six kilograms over 3 months. There was no previous history of TB or contact with known TB patients.
On examination, his face was puffy with central obesity and relatively thin limbs. Thinning of the skin was also noted. There was neither lymphadenopathy nor organomegaly. Warm, tender, nodular lesions of variable size and shape were found in the abdomen (Fig. 1), back and thigh. Some of them were ulcerated. The largest one was located on the back, measuring about 4 x 3 cm (Fig. 2). Both knee joints were swollen with Grade 2 tenderness and there was restricted movement in all directions with positive patellar tap. Muscle bulk and power were reduced symmetrically and proximally in both lower limbs. Muscle tone was unaltered with normal deep tendon reflexes and flexor plantar responses bilaterally.
Investigations revealed normal blood counts with high ESR (40 mm in 1st hour) and raised CRP (85.83 mg/L). S. creatinine was raised (1.7 mg/dL) and eGFR was low (30 ml/min/1.73 m2). Urinalysis revealed no abnormality. Microscopy and culture of urine for acid fast bacilli (AFB) were negative. Aspiration of pus from skin lesion revealed numerous AFB on staining (Fig. 3). Skin biopsy revealed perivascular infiltration of chronic inflammatory cells with mild acanthosis and exocytosis of epidermis. MTB-PCR of skin biopsy detected MTB DNA which was susceptible to Rifampicin. Culture of pus in Mycobacteria growth indicator tube (MGIT) revealed growth of MTB (Fig. 4). Sputum smear for acid fast bacilli (AFB) and culture for Mycobacterium tuberculosis were negative. High-resolution computed tomography (HRCT) of the chest and colonoscopy were performed to look for the primary focus of TB, but both were found to be normal. CT scan of abdomen and pelvis were normal as well. Tuberculin skin test was negative. A repeat test was performed after 8 weeks which was negative as well. 24 h urinary free cortisol was well above the normal range, measuring 227.05 mcg/day (Normal range: 50-190 mcg/day). Rheumatoid factor, anti-citrullinated protein antibody (ACPA) and HLA-B27 were negative with normal findings in plain X-ray and MRI of both SI joints. Early osteoarthritic changes were noted in plain X-ray of both knee joints.
He has been given anti-tubercular therapy comprising isoniazid, rifampicin and pyrazinamide in full dose and ethambutol with renal modification. After one month of taking the anti-tubercular drug, his skin lesions improved significantly.