Renal involvement and favorable outcome in a child with mastocytosis

Mastocytosis is a rare myeloproliferative disease in which mast cells abnormally accumulate in the skin, bone marrow, intestine, liver, spleen, and lymph nodes. Characterized by uncontrolled proliferation of aberrant mast cells, the disease can present either cutaneously or systemically. Mast cells facilitate the immune response and inflammation, and mastocytosis with renal involvement has been rarely reported in adults. Here, we describe a pediatric case of renal involvement in a patient with mastocytosis. A 12-year-old female with mastocytosis was admitted for edema, foamy urine, and gross hematuria. Initial laboratory findings showed azotemia, proteinuria, and hematuria. Renal biopsy findings were compatible with diffuse proliferative glomerulonephritis (DPGN). Immunofluorescence analysis of CD117 (c-Kit) staining resulted positive for rare infiltrating cells. These findings are unusual for primary glomerulonephritis (GN), and secondary GN is typically associated with mastocytosis. According to the literature, steroid treatment can be attempted in cases with renal disease associated with systemic mastocytosis. Therefore, the patient was treated with oral prednisolone, and proteinuria and hematuria disappeared after 4 months of treatment. After 5 months, prednisolone treatment was stopped, and the skin lesion improved. The renal function 22 months after prednisolone treatment was normal. This is a unique report of mastocytosis with DPGN in a child. c-Kit staining can be helpful for diagnosis, and the response to steroid treatment is favorable. Further study about the pathological relevance between mastocytosis and GN is necessary.