The alternate complement pathway. A possible role in a patient with focal glomerular sclerosis.

A boy had focal segmental glomerular sclerosis after the resolution of an unusual transient functional defect in activation of the alternate complement pathway. Prior to 1 year of age, the patient suffered repeated serious bacterial infections that were associated with an inability to opsonize Escherichia coli ON 2 in vitro. Serum levels of complement components were normal. Shortly after resolution of the complement defect, nephrotic syndrome developed. Properdin and C3 were identified in sclerotic glomeruli, which suggests that the ability to activate the alternate complement pathway played a role in the pathogenesis of glomerular sclerosis.