[Hypertriglyceridemia, Chronic Kidney Disease, and Proteinuria: A Rare Case of Apolipoprotein C-II Amyloidosis].

Abstract

We report the case of a 64-year-old man referred for evaluation of progressive renal dysfunction associated with hypertriglyceridemia and non-nephrotic proteinuria. There was no evidence of plasma cell dyscrasia, chronic inflammatory disease, or other secondary causes of amyloidosis. Renal biopsy revealed amyloid deposits with predominant glomerular involvement. Congo red staining confirmed the presence of amyloid, showing characteristic apple-green birefringence under polarized light. Immunohistochemical studies were non-diagnostic. Therefore, laser microdissection followed by mass spectrometry-based proteomic analysis was performed and identified apolipoprotein C-II (ApoC-II) as the main component of the amyloid deposits. Genetic analysis subsequently demonstrated a heterozygous c.122A>C (p.Lys41Thr) variant in the APOC2 gene, confirming the diagnosis of hereditary apolipoprotein C-II-related amyloidosis (AApoC-II), a very rare form of hereditary amyloidosis with predominant renal tropism.