A patient with progressive systemic sclerosis (PSS) involving skin, digit, esophagus, and lung developed the nephrotic syndrome and rapidly progressive renal insufficiency. Renal pathology revealed capillary collapse, cellular crescents, arteriolar hyaline deposition, and mesangial proliferation. On immunofluorescence IgM, C3, and fibrinogen were present in mesangium and capillary walls. Prebiopsy coagulation screening revealed a factor X deficiency which caused substantial prolongation of the partial thromboplastin time without an overt bleeding diathesis. The acquired factor X deficiency resolved after fresh frozen plasma and vitamin K administration, although some spontaneous improvement was noted. Nephrotic syndrome may occasionally be seen in the acute fulminant form of PSS and should not deter diagnosis of PSS.