1098 Atrial thickening: a surprisingly "gouty" heart

Abstract Case Presentation A 49 year-old male presented to the emergency department with fever and lower limb myalgia for 5 days. His past history was notable for acute episodes of microcrystalline pyrophosphate oligoarthritis for which he was receiving allopurinol 100mg, colchicine 1mg and prednisolone 5mg. Physical examination was unrevealing. Laboratory workup showed normocytic normochromic anemia (Hb 12.8g/dL), leukocytosis (22 490 /mm3), neutrophilia (86.8%), increased C-reactive protein (CRP 26mg/dL), low procalcitonin (0.82ng/mL) and mildly elevated creatinine-kinase (83 UI/L). The patient was admitted with fever of unknown origin and started on ceftriaxone after blood and urine cultures. He remained febrile with persistently heightened inflammation. Cultures, infectious and auto-immune tests, bone marrow biopsy, myelogram and abdominopelvic CT scan were negative. Three weeks later, syncope due to complete atrioventricular (AV) block led to temporary pacemaker implantation. Transoesophageal echocardiography (TOE) revealed a left atrial (LA) wall thickening, evident on MRI as an 8-10mm T2-hyperintensity sign, with right atrial (RA) and ventricular sparing. PET/CT scan showed an 18F FDG uptake exclusively in the LA. As a neoplasia was highly suspected, a transspeptal biopsy was attempted, yet the sample was scarce for analysis. Thus, a biopsy via sternotomy was performed, now sampling both the LA and RA. Indeed, repeated TOE showed de novo RA involvement with a prominent nodular finding (19x24mm) in the lateral wall. Myocyte inflammation and necrosis accompanied with granulocyte infiltration (mostly neutrophils but also eosinophils) was observed in all samples. There were no findings suggestive of neoplasia. The patient was still on allopurinol, which has been reported to involve the myocardium in a late (type IV) hypersensitivity reaction (the so-called DRESS syndrome), even in the absence of systemic inflammation. Thus, allopurinol was stopped and 1mg/Kg prednisolone was started. The patient significantly improved and was discharged home with negative CRP the following two weeks. After 1 month, MRI was repeated and no atrial inflammation was found. After 4 months follow-up, he is doing well on 2.5mg of prednisolone and febuxostat 80mg.