Endocrine Abstracts

JOINT1048

Introduction: Reninoma, also referred to as juxtaglomerular cell tumour, is a renin-producing, typically benign lesion that originates from the juxtaglomerular cells of the afferent arterioles within the renal glomeruli. It represents a rare cause of secondary hyperaldosteronism. To date, approximately 200 cases of reninoma have been reported, with histologically confirmed metastasis described in only five patients.

Case report: This case study presents the medical history of a 26-year-old male patient with therapy-resistant hypertension and hypokalaemia, diagnosed with hyperreninemic hyperaldosteronism in 1972. Despite the extensive imagining procedures performed, the underlying cause was finally identified in 2004 when an abdominal CT scan revealed a right renal mass. The histopathological analysis of the removed tumour established the diagnosis of reninoma based on the positive immunohistochemistry results for renin and CD34 and the rhomboid-shaped renin proto-granulate crystals identified by electron microscopic examination. After 10 years of clinical remission, the patient exhibited signs of recurrent hyperreninemic hyperaldosteronism (2014). Histological investigation performed after the selective removal of a neoplastic lesion in the left kidney once again confirmed reninoma. The patient, who had developed chronic renal failure, underwent successful kidney transplantation after 2 years of regular haemodialysis (2017). Six years later, in 2023, a routine abdominal CT scan revealed solitary masses in the liver and the spleen. A biopsy of the hepatic lesion established the clinical and histological diagnosis of a bilateral, metastatic reninoma. Considering the excellent general condition of our patient at the age of 78, our multidisciplinary endocrine tumour board recommended an atypical hepatic resection and splenectomy, which was performed in 2024 (R0 resection). Following an uneventful postoperative course, based on follow-up imaging, the patient remains tumour-free. The exceptionally slow, multidecade-long progression and bilateral manifestation of the tumour suggest the etiological role of a genetic factor. Whole-exome sequencing identified a previously unreported mutation in the ARMC5 gene, whose role in the tumorigenesis remains to be clarified.

Conclusion: To our knowledge, this is the first reported case of malignant reninoma with bilateral manifestation. The bilateral presentation of our case strongly suggests the involvement of genetic factors, but the role of the identified germline ARMC5mutation in reninoma pathophysiology requires further investigation.