The diagnosis of this disorder depends on demonstrating: 1) a dysfunctional plasma fibrinogen, i.e. significantly less functionally-detected compared to immunologically-detected fibrinogen; b) presence of signs and/or symptoms of kidney disease; and c) histological evidence of often massive obliteration of renal glomeruli by amyloid as detected by Congo red staining. There also should be no evidence for systemic amyloidosis. Specialized centers use immunological and genetic studies to define the nature of the renal amyloid deposits, the presence of FGA gene mutations, and the occurrence of these mutations in family members.