Sweet syndrome with reactive lymphadenopathy mimicking metastatic disease in an SDHB -mutated abdominal paraganglioma

We describe a case of Sweet syndrome, an acute neutrophilic dermatosis that may occur as a paraneoplastic manifestation. A 25-year-old man presented with recurrent abdominal pain and painful erythematous plaques on the trunk and upper limbs, without symptoms of catecholamine excess. Imaging revealed a retroperitoneal mass and extensive hypermetabolic lymphadenopathy on positron emission tomography/computed tomography using fluorine-18 fluorodeoxyglucose (18F-FDG) and gallium-68 DOTA–Tyr3–octreotate (68Ga-DOTATATE), raising concern for metastatic disease. Skin biopsy confirmed Sweet syndrome, while lymph node biopsies demonstrated reactive lymphoid hyperplasia. A computed tomography–guided biopsy of the retroperitoneal mass established the diagnosis of paraganglioma, but was complicated by hypertensive crisis. Subsequent biochemical evaluation revealed markedly elevated plasma normetanephrine levels despite normotension. The patient underwent preoperative alpha-adrenergic blockade followed by surgical resection. Cutaneous lesions resolved rapidly after tumor removal, and plasma normetanephrines normalized, confirming biochemical cure. This case highlights an association between Sweet syndrome and succinate dehydrogenase complex iron-sulfur subunit B (SDHB)-related paraganglioma and underscores the risk of false-positive metastatic findings on functional imaging and reinforces the importance of biochemical exclusion of paraganglioma before biopsy of vascularized retroperitoneal masses.