Cyclosporine A causes maturation failure in embryonic-type glomeruli persisting after birth.

Introduction: We analyzed renal histologic and immunohistologic findings in children with nephrotic syndrome (NS) who did (n=5) or did not (n=17) develop cyclosporine A (CyA) nephropathy despite appropriately low serum CyA concentrations being maintained over 2 years.

Methods: To discriminate embryonic-type from mature glomeruli, we performed staining for type IV collagen a1, laminin ß1 and laminin ß2. Staining patterns were used to semiquantitatively assess glomerular immaturity (glomerular immaturity index, or GII).

Results: In follow-up biopsy specimens, residual embryonic-type, collapsed embryonic-type and sclerotic glomeruli that had failed to differentiate were observed. Patients with early-onset CyA nephropathy had a high GII. In patients with a high GII, arteriopathy developed early in CyA treatment. Arteriopathy was observed mostly near embryonic-type glomeruli. Taken together, these glomeruli (surviving embryonic-type, collapsing embryonic-type, and sclerotic glomeruli) essentially equaled the total number of embryonic-type glomeruli in specimens obtained before CyA treatment.

Conclusion: Our findings indicate a need for caution in CyA therapy for patients with NS, even for a relatively short course of administration, because some patients may have embryonic-type glomeruli or immature arterioles that predispose them to CyA nephropathy.