Monoclonal Gammopathy of Renal Significance with Deposits of Infrequent Morphology: Two Case Reports of Light and Heavy Chain Deposition Disease with Atypical Presentation and Literature Review.

BACKGROUND: Monoclonal immunoglobulin deposition disease (MIDD) includes three entities: light chain deposition disease (LCDD), heavy chain deposition disease (HCDD) and light and heavy chain deposition disease (LHCDD). The renal presentation can manifest with varying degrees of proteinuria and/or nephrotic syndrome, microhematuria, and often leads to end-stage renal disease. Given the rarity of LHCDD, therapeutic approaches for this condition remain inconclusive, as clinical trials are limited. CASE PRESENTATION: We report two male patients with underlying monoclonal gammopathy of renal significance (MGRS) associated with LHCDD lesions. Both cases had non-nephrotic proteinuria, moderately impaired renal function, and normal levels of C3 and C4. Light microscopy of the renal biopsies in both patients did not show lesions of nodular glomerulosclerosis. Immunofluorescence showed a staining pattern with interrupted linear IgA-κ in patient #1 and IgA-λ in patient #2 only along the glomerular basement membrane (GBM). Electron microscopy of patient #1 revealed electrodense deposits in the subendothelial and mesangial areas only along the GBM. DISCUSSION: In this case series, we discuss the clinical, analytical, and histopathological findings of two rare cases of LHCDD. Both patients exhibited IgA monoclonality and were diagnosed with monoclonal gammopathy of undetermined significance (MGUS) by the hematology department at the time of renal biopsy. Treatment with steroids and cytotoxic agents targeting the clone cells responsible for the deposition disease resulted in a favorable renal and hematologic response.

Tumores renales sincrónicos: carcinoma renal de células claras y linfoma B de bajo grado, tipo MALT / Synchronous kidney neoplasms: renal carcinoma, clear cells type, and B lymphoma, low grade, MALT type

Introducción: Los linfomas MALT que afectan al riñónson muy raros; siendo la primera descripción la de Pelstringy colaboradores en 1991. Pacientes y métodos: Presentamosun caso de un varón de 71 años al que se le practicó unanefrectomía radical por laparoscopia. En el estudio delriñón se observaron un carcinoma renal, tipo de células claras,y un linfoma B, tipo MALT. Conclusiones: La presenciasimultánea en el riñón de un carcinoma renal y un linfomaMALT es extremadamente rara. Los linfomas MALTque surgen en el riñón podrían estar relacionados con unaenfermedad autoinmune, como el síndrome de Sjögren, ocon la inflamación crónica, como las pielonefritis (AU)

Introduction: Mucosa-associated lymphoid tissue(MALT) lymphoma involving the kidney is extremely rare;and was first reported in 1991 by Pelstring et al. Patientsand methods: We report a case of 71 year-old man underwenta radical nephrectomy by laparos copy. Pathologicalstudy of the kidney revealed a renal cell carcinoma, clearcell type, and a B-cell lymphoma, MALT type. Conclusions:The simultaneous occurrence in the kidney of a renalcarcinoma and MALT lymphoma is extremely rare. MALTlymphoma arising from the kidney could be associated withautoinmune disease such as a Sjögren syndrome or withchronic inflammation, such as pyelonephritis (AU)