Familial thin basement membrane nephropathy in children: Immunofluorescence studies of the familial nephritis antigen in skin biopsy specimens

Hereditary nephritis is a frequent cause of persistent glomerular hematuria. This disorder spans a clinical spectrum from an illness characterized by progressive loss of renal function to a relatively benign abnormality marked solely by the finding of hematuria. At the present time, the only means of discriminating between these two entities is by examining the ultrastructural appearance of the glomerular basement membrane and detecting splitting end lamination versus predominant thinning of the lamina densa. We investigated whether performing a skin biopsy end immunofluorescence staining of the epidermal tissue for the familial nephritis antigen could assist in distinguishing these two disorders. Nine children (3 males) with biopsy proven thin basement membrane nephropathy were studied. All patients had normal renal function and only one had abnormal urinary protein excretion. A 4 mm punch biopsy of the skin was done and the tissue was examined for the binding of an antiserum derived from a patient with Alport syndrome who developed anti-GBM antibody glomerulonephritis following renal transplantation. The immunofluorescence staining pattern was indistinguishable from normal controls in all 9 patients. We conclude that a skin biopsy may be a useful adjunct in the evaluation of patients with hereditary nephritis since detection of the familial nephritis antigen in children with familial thin basement membrane nephropathy indicates that these patients are distinct from those with severe hereditary nephritis or Alport syndrome. Their long term prognosis for maintenance of normal renal function is excellent.