What is scleroderma renal crisis (SRC)?
Renal failure, one of the most feared complications of SSc, may present as acute renal crisis after prolonged hypertension and less commonly as normotensive renal failure. SRC occurs in up to 5% of the entire SSc population and in 5% to 20% of patients with dcSSc. Patients with early diffuse skin thickening, especially patients with RNA polymerase III antibody positivity, are at highest risk for SRC and vigilant surveillance is indicated. Renal crisis may be the presenting manifestation of SSc and can sometimes precede skin thickening. Generally, renal crisis occurs early in the course of the disease, with a mean onset of 3.2 years and more often in the fall and winter months. Serologically, the presence of RNA polymerase III antibody conveys a higher risk of SRC (antibody present in approximately 50% of cases of SRC, but <20% of SSc overall).
SRC typically presents with an abrupt onset of arterial hypertension (>150/90; although 10% are normotensive), appearance of grade III (flame-shaped hemorrhages and/or cotton-wool exudates) or grade IV (papilledema) retinopathy, and the rapid deterioration of renal function (within a month). Pericardial effusion is frequently present. Abnormal laboratory tests include elevated renal function tests, proteinuria, consumptive thrombocytopenia, microangiopathic hemolysis ( schistocytes; 50%), elevated renin levels (twice the upper limit of normal or greater), and normal or only mildly decreased ADAMTS 13 levels (>20% of normal). This latter test may be important given the similar clinical presentation of thrombotic thrombocytopenic purpura/hemolytic uremic syndrome and SRC. In addition, a subset of patients with SSc may suffer acute renal failure secondary to an antineutrophil cytoplasmic antibody (ANCA)-associated glomerulonephritis, another potential mimicker of SRC. However, these patients do not typically present with the hemolytic manifestations of SRC, hypertension does not predominate to the same degree, and they can be distinguished by laboratory evaluation (red blood cell casts, ANCA antibody) and biopsy.
Approximately 50% of patients who develop SRC will require dialysis, but nearly half of these patients will be able to discontinue dialysis after 3 to 18 months on ACE inhibitor therapy. Five-year mortality is still significant and ranges from 20% to 40% in the literature.