Pseudolinear C4d deposits in a hereditary glomerulopathy caused by a rare NC1 collagen-4-alpha-5 missense mutation: a "new disease entity"?

C4d positive glomerulopathies with pseudolinear capillary wall deposits caused by basement membrane (GBM) remodeling have sporadically been reported in renal transplants. Here we describe the case of a hypertensive 60 year-old male with a 5 month history of nephrotic range proteinuria in the setting of normal serum creatinine, complement and ANA levels. Work-up showed MGUS (IgG/kappa restricted). A diagnostic renal biopsy to search for monoclonal gammopathy of renal significance demonstrated thickened glomerular capillary walls with strong pseudolinear complement factor C4d deposits by immunofluorescence microscopy (IF); all other IF studies including stains for