Indolent systemic mastocytosis associated with light chain deposition disease

Abstract

Systemic mastocytosis (SM) is characterized by infiltration of neoplastic mast cells in one or more organ systems. SM in association with plasma cell dyscrasia is very rare. We report a first case of indolent SM (ISM) associated with light chain deposition disease (LCDD) in a kidney biopsy from a 59-year-old female presenting with skin rash, elevated serum creatinine, hematuria and mild proteinuria. Subsequent workup demonstrated IgG kappa monoclonal protein in serum and urine. A bone marrow biopsy revealed neoplastic mast cells involving bone marrow without evidence of clonal myeloid or lymphoid proliferation. Kidney biopsy demonstrated modest mesangial expansion detected by light microscopy and unequivocal evidence of monoclonal kappa light chain deposition within glomerular capillaries, tubular basement membranes and vascular walls detected by immunofluorescence and/or electron microscopy, along with equivocal evidence of light chain cast nephropathy. Despite treatment with bortezomib and dexamethasone, her renal function was progressively declined over the next 6 months. This case is a reminder that SM can coincide with LCDD, which requires clinical suspicion and multimodality workup on a kidney biopsy including immunofluorescence and electron microscopy to reach the correct diagnosis.

Systemic mastocytosis with renal light chain amyloidosis: associated non-mast cell disorder or concurrent disease

“…Eight cases were diagnosed simultaneously where the associated PCN either monoclonal gammopathy of unknown significance (MGUS), smoldering multiple myeloma (SMM), or plasma cell myeloma (PCM) [8][9][10][11][12][13][14][15]. On the other hand, SM preceded light chain deposition NA, not available disease (LCDD) or PCM in two cases [16,17], while MGUS preceded SM in the remaining two cases [18,19]. Prior literature has hypothesized that mast cells play a role in the proliferation of malignant lymphocytes.…”