Beyond the Flank Mass: Unraveling a Rare Case of Concurrent Amyloidosis and Pheochromocytoma

Introduction: AA amyloidosis typically arises from chronic inflammation, and pheochromocytomas are known to induce systemic inflammation. Despite this connection, a clear relationship between these two conditions hasn't been well-established in literature. Here we present a case of AA amyloidosis suspected to be in the setting of a concomitantly diagnosed pheochromocytoma. Case Description: A 63-year-old female with a history of interstitial cystitis presented with an enlarging flank mass. Her presentation was complicated by AKI, with creatinine of 2 mg/dL (baseline of 0.9 mg/dL), microscopic hematuria (11-25 RBC per HPF), and a UPCR of 18.14 g/g. Serological workup showed elevated IgG4, ESR, and CRP. PLA2R antibody was negative, and no M protein was identified. MRI revealed an 18.6 x 14.3 x 18.4 cm heterogeneous cystic mass in the left adrenal gland, concerning for neoplasm, and a 16.8 x 9.1 cm heterogeneous mass with cystic and solid components extending from the left peritoneum into the left abdominal wall, concerning for a left kidney neoplasm. The Patient underwent an adrenalectomy with nephrectomy, and pathology revealed amyloidosis, renal parenchyma thyroidization, and tubulointerstitial fibrosis. Immunofluorescence staining showed no definitive uptake, but mass spectrometry identified serum amyloid A (SAA). Postoperatively, her condition improved, and she was discharged on a tapered dose of steroids. Discussion: Although direct evidence linking chronic inflammation in pheochromocytoma to the development of AA amyloidosis is lacking, the chronic inflammatory state seen in patients with pheochromocytoma could theoretically contribute to elevated SAA levels and subsequent amyloid deposition, especially if the inflammation is prolonged and severe. Further research is necessary to establish a direct causal relationship.