Renal involvement in patients with thrombotic thrombocytopenic purpura.

A retrospective review of the records of 15 patients with thrombotic thrombocytopenic purpura (TTP) was performed to determine the spectrum of renal involvement that occurs in this disease. All cases exhibited some evidence of renal involvement, the most common manifestation of which was an abnormal urinalysis. Twelve cases (80%) had some degree of elevation of the serum urea nitrogen (SUN) or creatinine level at some time during the course of their disease. Renal involvement could be categorized into three types depending on the severity of TTP. In those cases presenting as an acute devastating illness, renal insufficiency, when present, was severe and a dominant component of the disease. In those that pursued a more protracted course, with subsequent acute exacerbations of TTP, renal insufficiency was variable and less severe than in the first group. In those presenting with a mild form of TTP, renal involvement consisted primarily of an abnormal urine sediment and azotemia that corrected rapidly following fluid replacement. A review of the literature beginning with 1966, when renal disease was established as part of the features that characterize TTP, provided 216 cases in whom sufficient data on renal involvement were recorded. Of the 168 cases where urinalysis was reported, hematuria was noted in 78% of the cases, proteinuria in 75, pyuria in 31, and cylindriuria in 24%. Of the 181 cases where the admission SUN was reported, it was higher than 20 mg/dl in 69% and greater than 60 mg/dl in 17% of the cases. The level of SUN was a significant determinant of the final prognosis of these patients.