Renal biopsy specimens were examined in a group of 65 patients with primary hematuria who met the following criteria: urine protein excretion under 1 g in 24 hours or a negative Albustix® in a concentrated specimen, absence of hypertension and normal renal function. The median age at discovery of the disease was 13 years, and the median duration of the hematuria at biopsy was two years. Recurrent gross hematuria was present in 38 instances. Thirty of the 65 renal biopsy specimens showed mesangial proliferative glomerulonephritis and in 44 there were red blood cells in the tubules. Mesangial deposits of a variety of immunoglobulins and/or third component of complement (C3) were identified in 30 of the 44 biopsy specimens examined. Immunoglobulin M (IgM) was the predominant immunoglobulin. Electron dense mesangial deposits were identified only in 12 cases; however, ultrastructural study of the biopsy specimens led to the detection of one patient who was probably suffering from Alport's syndrome. There was a poor correlation between histologic lesions and immunohistochemical findings. Thirty-nine patients were followed for a median period of four years without evidence of any deterioration of renal or any other manifestation of renal or systemic disease, although half of these patients still showed bleeding in the last urinalysis. Thus, the name benign primary hematuria appears appropriate to designate this clinical syndrome. The use of pathologic terms such as focal glomerulonephritis or immunoglobulin A (IgA) nephropathy (Berger's disease) has been a cause of ambiguity since there is not a consistent correlation between these lesions and clinical manifestations. Because the discrete mesangial changes may be predicted virtually from the clinical presentation, kidney biopsy may not seem to be indicated in the majority of these patients unless there is an increase in urinary protein excretion or other manifestations of renal, genitourinary or systemic disease appear.
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