Grossly, cerebral and cerebellar atrophy is present in all clinical types, but the severity varies greatly, being very severe in the infantile and late infantile and only moderately severe in the juvenile and adult diseases (Figs. 9.5, 9.6, and 9.7).

Histologically, the neuronal storage is most prominent in the infantile and late infantile variants. Ballooned neurons dominate throughout the brain in the early stage. Severe neuronal losses in the cerebral and cerebellar cortex and deep gray structures dominate in the late stage (see Fig. 9.5). Astrocytosis parallels the neuronal losses. The white matter shows variable myelin degeneration and astrofibrosis. Neuronal storage and losses are moderate in the juvenile and adult variants.

The stored compound is composed of proteolipids combined with saccharides. The protein component consists of two fractions: (a) subunit C of the mitochondrial ATP synthase (SOMAS) and (b) saposin (SAP). The compound autofluoresces in ultraviolet light, stains positively with oil-red O, Sudan black B, and PAS. It displays various ultrastructural patterns, distinct for each major disease: granular deposits in early infantile, curvilinear bodies in late infantile, and fingerprint-like deposits in juvenile NCL. Storage without conspicuous cell losses occurs in the viscera, vascular endothelium, sweat glands, skin, and muscles.

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