We report a case of anti GBM disease that developed in the renal graft of a patient with Alport syndrome. After reaching abnormal values of creatinine, the patient presented with deteriorating renal function three months after a cadaver transplant and the biopsy showed crescent formation, and linear IF deposits. Circulating antibodies against alpha 5 chain of type IV collagen were found and plasmaphereses stabilized the condition for one year until a lung infection led to withdrawal of the immunosuppressive drugs and the patient returned to dialysis. We discuss the possible mechanisms underlying the specificity of the circulating antibodies in this case, which differs from the target characteristic of the idiopathic form of anti GBM disease, the alpha 3 (IV) chain.