Clinical Neuropathology image 1-2015: Crystal-storing histiocytosis of the central nervous system

Crystalloid inclusions are rarely encountered within the central nervous system (CNS). Aside from the more common Hirano bodies and Rosenthal fibers, which occur within neurons and astrocytic processes, both being composed of cytoskeletal proteins, eosinophilic crystalloid inclusions have been recently described within oligodendrocytes in a case of adult-onset, complicated form of hereditary spastic paraplegia [1]. However, crystalloid inclusions may also accumulate within macrophages referred to as crystal storing histiocytosis (CSH). CSH is a rare condition, which most often occurs within the setting of lymphoproliferative disorders, in which immunoglobulins aggregate within the cytoplasm of macrophages [2]. Localized and generalized forms of CSH are distinguished based on the extent of organ involvement [3]. While the lymphoreticular system, bone marrow, kidney, and lung are most often affected, CNS presentation is extremely rare with 5 cases reported in the literature, so far [2, 3, 4, 5, 6, 7].