Maternally inherited diabetes and deafness complicated by mesangial galactose-deficient IgA1 deposits: a case report

BackgroundMaternally inherited diabetes and deafness (MIDD), a mitochondrial genetic disorder, typically affects the kidneys and results in end-stage renal disease. Early diagnosis of MIDD is challenging when renal manifestations precede other key clinical features such as diabetes and deafness and/or when the disease is complicated by other renal pathologies.Case presentationHere, we present the case of a 33-year-old Japanese woman who had initially been diagnosed with IgA nephropathy but was found to have MIDD 6years later. Two renal biopsies were conducted six years apart. While assessment of the first biopsy specimen with the monoclonal antibody (KM55) revealed mesangial IgA deposits (containing the galactose-deficient IgA1 variant [Gd-IgA1]), examination of the second specimen showed no mesangial IgA deposits and newly-developed glomerular global scleroses and tubular damage. Granular swollen epithelial cells (GSECs), characterised by abnormal mitochondria, were observed among the tubules and collecting ducts in both biopsy specimens. Mitochondrial DNA analysis revealed an m.3243A>G mutation.ConclusionsWe rediscovered the usefulness of GSECs as a pathologically distinctive feature of mitochondrial nephropathy and reviewed the literature regarding MIDD complicated by mesangial IgA deposition. Furthermore, we demonstrate that the mesangial IgA deposits in this patient consisted of the galactose-deficient IgA1 variant. The monoclonal antibody (KM55) might be a useful tool to distinguish IgAN from latent IgA deposits.