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Título

RENAL IGG HEAVY CHAIN (AH) AMYLOIDOSIS AS MONOCLONAL GAMMOPATHY OF RENAL SIGNIFICANCE - FROM ACCURATE DIAGNOSIS TO ADEQUATE TREATMENT

Relato do Caso

Monoclonal Gammopathy of Renal Significance (MGRS) is a B-cell or plasma-cell clonal disorder that does not meet the criteria for cancer but produces a monoclonal immunoglobulin that leads to kidney injury. It can rarely manifest as AH amyloidosis, in which highly ordered heavy-chain fibrils deposit in the kidneys. We report a case in which a patient with MGRS was diagnosed and treated for renal AH Amyloidosis.

A 77-year-old patient was referred to our Nephrology Clinic due to chronic kidney disease (1.4mg/dL baseline creatinine), proteinuria (2.2g/24h), monoclonal gamma spike (0.75g/dL), hypertension and bilateral feet paresthesia. Bone marrow biopsy showed 6% plasmocyte clonal proliferation. Eletrocardiogram, echocardiogram, myocardial scintigraphy and bedside kidney ultrasound were unremarkable. Further workup showed 8.7g/dL hemoglobin, 1.28mmol/L ionized calcium, 6.3 Kappa-to-Lambda ratio, IgG/Kappa on immunofixation, 1058 mg/dL IgG and rare erythrocytes and 2+ protein on urinalysis. Renal biopsy was performed for suspected MGRS with glomerular involvement and revealed PAS-pale, silver-negative, Congo-Red positive mesangial deposits with apple-green refringence under polarized light. Immunofluorescence showed diffuse global glomerular IgG positivity with negative Kappa and Lambda. AH Amyloidosis was diagnosed and CyBorD chemotherapy started. After 4 sessions, creatinine and blood urea nitrogen levels improved from 2.2mg/dL and 60.2mg/dL to 1.58mg/dL and 30mg/dL respectively. Proteinuria reached 0.86g/24h.

This is a case of rare renal AH Amyloidosis diagnosed in a patient with hypertension, subnephrotic proteinuria and isolated kidney injury, which differs from the typical hypotension, nephrotic-range proteinuria and multi-organ involvement seen in AL Amyloidosis. Since elevated serum free light-chain levels might be seen on both conditions, renal biopsy is vital for precise diagnosis and fibril deposit distinction. As new therapies are surging for MGRS and Amyloidosis, there is a need for prompt suspicion and accurate diagnosis, which can improve renal outcomes, mitigate disease burden and prevent overt malignancy such as multiple myeloma.

Palavras Chave

Amyloidosis, Heavy Chain, Glomerulus, Onconephrology, Proteinuria