A Periodic Curveball: Collagenofibrotic Glomerulopathy

Introduction: Collagenofibrotic Glomerulopathy is a rare idiopathic disease with unknown pathogenesis and no treatment. Case Description: A 65-year-old man with hypertension and tobacco use disorder was hospitalized after 5 months of fevers, rigors, weight loss, malaise and one week of heavy acetaminophen and ibuprofen use. He was treated for acetaminophen toxicity and received extensive infectious and hematologic workup, which revealed multiple hypermetabolic lymph nodes on PET CT with necrotizing lymphadenitis on biopsy and prostatomegaly with intermittent bleeding on cystoscopy. Nephrology was consulted for microscopic hematuria, spot urine protein:creatinine ratio 524 mg/g, and 117 mg/g albuminuria. Creatinine was 0.9 mg/dL with estimated glomerular filtration rate 90 ml/min/1.73m2. Serologic workup was negative aside from antinuclear antibody titer of 1:80. Urine microscopy showed acanthocytes. Subsequent renal biopsy showed mesangial and subendothelial deposits of curved fibrils with frayed edges and transverse banding at 60 nm periodicity, consistent with collagenofibrotic glomerulopathy (Figure). Two years later, renal function remains preserved with mild proteinuria and microscopic hematuria. The etiology of his B-symptoms remains unconfirmed. He has been treated with valsartan and dapagliflozin. Rheumatology initiated methotrexate for suspected systemic autoimmune inflammatory syndrome. A recent repeat bone marrow biopsy revealed chronic monomyelocytic leukemia stage 0. Discussion: Collagenofibrotic glomerulopathy is identified by atypical type III collagen deposition in the mesangium and subendothelium. Limited case reports note hypertension, mild proteinuria, microscopic hematuria and typically preserved renal function, consistent with this case. Interestingly, this mysterious disease was found amid a mysterious constellation of symptoms. It is classically not linked with extrarenal symptoms at diagnosis, but re-evaluation of known cases should be considered for later development of hematologic or rheumatologic disease.Electron Microscopy