Abstract

Background: Sarcoidosis, a systemic inflammatory disease characterized by nonnecrotizing granulomas, presents significant diagnostic challenges, particularly in regions like India where tuberculosis (TB) is highly endemic. Both conditions share clinical, radiological, and even some histological features, leading to potential misdiagnosis. This confusion is especially pertinent when sarcoidosis manifests with atypical radiological patterns, such as a miliary pattern, classically associated with disseminated TB. Accurate differentiation is critical, as the standard immunosuppressive therapy for sarcoidosis can have deleterious effects if administered for unrecognized TB. Case Presentation: We present the case of a 45-year-old male residing in Kolkata, West Bengal, India, with comorbidities of type 2 diabetes mellitus and hypertension, who presented with a two-month history of progressive exertional dyspnea, dry cough, and chest discomfort. High-resolution computed tomography (HRCT) of the thorax revealed diffuse bilateral micronodules consistent with a miliary pattern, raising strong initial suspicion for miliary TB. However, comprehensive investigations were pursued. Sputum examinations for acid-fast bacilli (AFB) were repeatedly negative, as was polymerase chain reaction (PCR) for Mycobacterium tuberculosis in bronchoalveolar lavage (BAL) fluid. Fiberoptic bronchoscopy with transbronchial lung biopsy (TBLB) was pivotal, demonstrating multiple wellformed non-necrotizing epithelioid cell granulomas, characteristic of sarcoidosis. Serum angiotensin-converting enzyme (ACE) levels were notably elevated at 140 U/L. Fungal cultures and other relevant investigations were negative. Conclusion: Based on the compatible clinical picture, supportive ACE levels, exclusion of infectious etiologies (particularly TB), and definitive histopathological findings, a diagnosis of pulmonary sarcoidosis was confirmed. The patient was initiated on oral corticosteroids, with mycophenolate mofetil added early due to concerns regarding poor glycemic control. This case strongly emphasizes that sarcoidosis must be considered a key differential diagnosis for miliary patterns on chest imaging, even in high TB prevalence settings. It highlights the insufficiency of relying solely on radiological findings and underscores the essential role of histopathology via TBLB or other biopsy methods for accurate diagnosis, thereby preventing inappropriate anti-tuberculosis treatment and enabling timely, targeted therapy for sarcoidosis.

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