IgA nephropathy complicated with cross reactive material (CRM)-positive congenital factor XI abnormality

Abstract

A 20-year-old man presented with proteinuria of increasing intensity, and persistent microhematuria. His renal biopsy findings were compatible with the diagnosis of IgA nephropathy, with diffusely increased mesangial matrix in the glomeruli shown on light microscopy and granular IgA deposition in the mesangium shown on immunofluorescence microscopy. Although his bleeding time and platelet counts were normal, he had a prolonged activated partial thromboplastin time (APTT). Coagulation studies showed that factor XI activity was decreased, to 39%. We immunoblotted plasma samples obtained from the patient and from one normal individual with polyclonal anti-human factor XI, and demonstrated that the factor XI antigen level of the patient was comparable to that of the normal control. A family study showed that the father of the patient had a similar coagulation abnormality, with normal factor XI antigen level. These findings suggest that the patient has a congenital factor XI abnormality with cross-reactive material positivity complicating IgA nephropathy. The findings imply the possible importance of clotting disorders in the pathogenesis and/or development of IgA nephropathy.