CTICasesHypersensitivity Pneumonitis Misdiagnosed as Sarcoidosis
Imaging findings
A patient carrying a longstanding diagnosis of sarcoidosis, not responding to immunosuppressive therapy, has serial CTs over several years showing centrilobular ground-glass nodules and lobular areas of ground-glass attenuation with sharply defined interlobular septa and fissures, indicating the ground-glass is centrilobular rather than perilymphatic/along the fissures as would be typical of sarcoidosis; the lungs appear diffusely gray with a subtle "black bronchus" sign of unusually conspicuous airways against the abnormal parenchyma.
Key takeaways
A centrilobular, fissure-sparing ground-glass and nodular pattern with progressive disease despite sarcoid-directed immunosuppression should prompt reconsideration of hypersensitivity pneumonitis, especially once an antigen exposure is identified -- here, chronic exposure to down bedding and a down coat; biopsy showing non-necrotizing ("wimpy") granulomas can be non-specific and should not override an imaging pattern and clinical exposure history that argue against sarcoidosis, particularly in a patient without lymphadenopathy or extrathoracic sarcoid manifestations.
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