Novel crystalloid oligodendrogliopathy in hereditary spastic paraplegia.

Hereditary spastic paraplegia (HSP) comprises a group of clinically and genetically heterogeneous disorders associated with spastic paraparesis (pure HSP) with or without additional neurological symptoms (complicated HSP). Here we present a case of an adult-onset, apparently autosomal-dominant, complicated form of HSP. Onset of clinical symptoms was at the age 40 years and characterised by slowly progressive corticospinal tract dysfunction, dysarthria, disorientation, extrapyramidal symptoms, and bilateral ptosis. Cranial MRI revealed hyperintensities on T2-weighted sequences mostly in the posterior limb of the internal capsule. The proband deceased at the age of 64 years. As morphological substrate for the slowly progressive clinical symptoms, comprehensive neuropathological and ultrastructural evaluation revealed a novel oligodendrogliopathy with distinctive, partly ubiquitinated and p62 positive fibrillar inclusions evolving into crystalloid deposits, containing elements of the oligodendroglial cytoskeleton (α- and β-tubulin, TPPP/p25). In the central nervous system, accumulation of crystalloid structures has been related to histiocytes but not to glial cells. This study has implications for the understanding on how the human central nervous system reacts to protracted dysfunction and disruption of the oligodendroglial cytoskeleton, including development of crystalloid structures, which have not yet been reported in neurodegenerative diseases including HSP.