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.

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.