Cauda equina compression revealing brown tumor of the spine in a long-term hemodialysis patient.

Brown tumors, or osteoclastomas, are erosive bony lesions arising as a complication of hyperparathyroidism (HPT). In patients with end-stage renal disease (ESRD), brown tumors are classic skeletal manifestations usually seen in severe forms of secondary HPT. However, involvement of the spine is considered extremely rare. We report a long-term hemodialysis case, in which cauda equina compression developed due to a sacral brown tumor. A decompressive surgery and subtotal parathyroidectomy were indicated to preserve neurologic function, and to ensure remineralization of the lesion. This case illustrates that, though rare, brown tumors should be considered in uremic patients with neurological symptoms. Emergent decompressive surgery is required to remove pressure on neurological structures and to stabilize the spine.

Nephrotic syndrome revealing a disseminated Langerhans' cell histiocytosis.

Langerhans' cell histiocytosis (LCH) is a clonal disorder of proliferating histiocytes, which can affect various organs. The clinical picture ranges from localized to disseminated disease with multiple organ involvement and severe organ dysfunction. Renal involvement is uncommon and the association with glomerulonephritis is unusual. We report here a case of nephrotic syndrome caused by membranoproliferative glomerulonephritis (MPGN) in a 20-year-old woman, which revealed a disseminated form of LCH. Surgical removal of the LCH process and high doses of corticosteroids led to the remission of the basic disease and the renal involvement. The occurence of membranoproliferative glomerulonephritis in the course of LCH might be mediated by circulating immune complexes, composed at least in part of antigens or neoantigenes which may cause the abnormal proliferation of the Langerhans' cells.