Hypereosinophilic syndrome with pulmonary and hepatic involvement mimicking autoimmune disease

Abstract Idiopathic hypereosinophilic syndrome (HES) is defined as blood eosinophilia on at least 2 occasions or evidence of prominent tissue eosinophilia with exclusion of secondary causes, commonly affecting the lungs but rarely the liver. A 44-year-old woman presented with 18 months of progressive dyspnea, cough, and intermittent fever. Investigations revealed marked leukocytosis with hypereosinophilia, cholestatic pattern of liver enzyme elevation, and hypergammaglobulinemia. High-resolution computed tomography of the chest showed bilateral fibrotic changes suggestive of sarcoidosis. Antinuclear antibody testing was strongly positive with a cytoplasmic filamentous pattern, suggesting autoimmune hepatitis or eosinophilic granulomatosis with polyangiitis. Liver biopsy revealed pericellular and portal fibrosis, focal eosinophilic infiltration, mild hepatocellular cholestasis, and occasional multinucleated giant cells. After excluding mimics, a diagnosis of HES with isolated pulmonary and hepatic involvement was established. This case highlights the importance of considering HES in patients with longstanding respiratory symptoms and systemic findings, especially when autoimmune markers may be misleading.