Steroid-responsive idiopathic glomerular capillary endotheliosis: Case report and literature review

Glomerular capillary endotheliosis is a lesion of endothelial cell injury. Morphological characteristics are endothelial swelling with glomerular hypertrophy and a reduction in capillary lumen size. This lesion commonly is found in patients with thrombotic microangiopathy, but similar histopathologic characteristics have been reported in patients with other diseases. A previously healthy 39-year-old woman presented with progressive lower-extremity swelling and arthralgias for 1 week. She had no other symptoms and denied prior illness. Her examination was remarkable for hypertension and pitting edema. Urine showed dysmorphic red blood cells and proteinuria. Serum creatinine level increased from 1.1 to 2.0 mg/dL (97 to 177 μmol/L) during several weeks. She did not meet criteria for systemic lupus erythematosus. Other test results included a negative pregnancy test and normal complement levels. Additional workup was negative for other causes of glomerular capillary endotheliosis. She underwent 2 renal biopsies. The first showed marked endothelial cell swelling, and the second biopsy 2 months later showed disease progression. Both were consistent with glomerular capillary endotheliosis. Proteinuria and serum creatinine level elevation responded to methylprednisolone therapy within 1 week, recurred after steroid doses were tapered, and responded again after restarting steroid therapy with monthly cyclophosphamide infusions. The differential diagnosis for glomerular capillary endotheliosis is limited. Various causes have been implicated, such as dysregulation of vascular endothelial growth factor, abnormal collagen production, and endothelial abnormalities. We did not identify prior cases of idiopathic glomerular capillary endotheliosis in the literature. Idiopathic glomerular capillary endotheliosis may be a newly recognized entity potentially responsive to steroid and cytotoxic regimens.