Case Report: delayed recognition of pulmonary tuberculosis during immunosuppression for suspected connective tissue disease.

BACKGROUND: Pulmonary tuberculosis may be difficult to recognize in patients receiving immunosuppression for suspected connective tissue disease, because clinical symptoms, inflammatory markers, pulmonary abnormalities, and imaging findings may be attributed to autoimmune disease activity. CASE PRESENTATION: A 57-year-old woman with dry mouth, myalgia, arthralgia, and positivity for antinuclear antibody (ANA) and anti-SSA/SSB antibodies was initially considered to have Sjögren syndrome or undifferentiated connective tissue disease. She sequentially received glucocorticoids, belimumab, tocilizumab, and baricitinib. During treatment, she developed recurrent low-grade fever, marked weight loss, pulmonary nodules and consolidation, mediastinal lymphadenopathy, and painful subcutaneous nodules. Three TB-related T-cell immunological assays were negative, including two interferon-gamma release assay tests and one T-SPOT. TB assay. Biopsy of a subcutaneous lesion showed acute and chronic inflammation with suspected granuloma formation, and next-generation sequencing of the tissue did not identify a causative pathogen. Because fever persisted and respiratory symptoms subsequently developed, an infectious etiology was reconsidered, and respiratory microbiological testing was repeated. The sputum acid-fast bacilli smear was positive (3+), Mycobacterium tuberculosis complex nucleic acid testing showed a high DNA load, molecular resistance testing demonstrated rifampicin susceptibility, and sputum mycobacterial culture was subsequently positive. Anti-TB treatment with a 2HRZE/10HRE regimen was followed by defervescence, regression of the panniculitis-like lesions, smear conversion, culture conversion, and radiological improvement. CONCLUSION: Negative IGRA-related tests should not be used to exclude active TB in immunosuppressed patients. Persistent fever, weight loss, pulmonary lesions, lymphadenopathy, or granulomatous inflammation should prompt repeat microbiological testing before escalation of immunosuppression.