👤 M Philippart

The neuronal ceroid lipofuscinoses (NCL) are a large group of autosomal recessive lysosomal storage disorders with both enzymatic deficiency and structural protein dysfunction. Previously, diagnosis of NCL was based on age at onset and clinicopathologic (C-P) findings, classified as 1) infantile (INCL), 2) late infantile (LINCL), 3) juvenile (JNCL), and 4) adult (ANCL). Most patients with NCL have progressive ocular and cerebral dysfunction, including cognitive/motor dysfunction and uncontrolled seizures. After reviewing 319 patients with NCL, the authors found that 64 (20%) did not fit into this classification of NCL. With research progress, four additional forms have been recognized: 5) Finnish, 6) Gypsy/Indian, and 7) Turkish variants of LINCL and 8) northern epilepsy, also known as progressive epilepsy with mental retardation. These eight NCL forms resulted from 100 different mutations on genes CLN1to CLN8 causing different phenotypes (http://www.ucl.ac.uk/ncl). The genes CLN1 and CLN2 encode lysosomal palmitoyl protein thioesterase and tripeptidyl peptidase 1. The function of CLN3, CLN5, and CLN8 gene-encoded products is unknown, although their predicted amino acid sequences suggest they have a transmembrane topology. The diagnosis of NCL is based on C-P findings, enzymatic assay, and molecular genetic testing. Before biochemical and genetic tests are conducted, ultrastructural studies (i.e., blood [buffy coat] or punch biopsies [skin, conjunctiva]) must be performed to confirm the presence and nature of lysosomal storage material (fingerprint or curvilinear profiles or granular osmiophilic deposits). The recognition of variable onset from infancy to middle age supersedes the traditional emphasis on age-related NCL forms. Show less

Positron Emission Tomography (PET) with 2-deoxy-2 [18F]-fluoro-D-glucose provides a measure of functional brain activity, particularly in the dendritic field. In CLN3 (juvenile neuronal ceroid lipofuscinosis or juvenile Batten disease, with fingerprint inclusions) hypometabolism slowly spreads from calcarine to anterior areas, sparing subcortical structures and brainstem. In CLN2 (late infantile neuronal ceroid lipofuscinosis or Jansky-Bielschowsky disease, with curvilinear inclusions) degeneration is rapid with generalized cortical and subcortical hypometabolism. This is associated with rapidly progressive cerebral atrophy on anatomical neuroimaging. A 4-year-old child with CLN2 scanned with PET 13 months after the clinical onset showed hypometabolism, severe in the thalamus and mild in cortical areas. Three other patients with CLN2 had severe generalized hypometabolism and brain atrophy. Longitudinal PET studies in CLN may provide key insights into degenerative processes. Show less

A number of variant forms of the neuronal ceroid lipofuscinoses (NCL) have been described and remain unmapped. The genes for infantile (CLN1), juvenile (CLN3) and Finnish-variant late-infantile (CLN5) have previously been mapped to chromosome regions 1p32, 16p12 and 13q21.1-32 respectively. The locus for a variant form of juvenile onset NCL characterised by cytosomal granular osmiophilic deposits (GROD) has been excluded from the CLN3 region of chromosome 16. This study describes the outcome of genetic linkage analysis in four families with this variant at the loci for the CLN1 and CLN5 genes. Using highly informative microsatellite markers tightly linked to the CLN5 locus we have excluded the JNCL variant with GROD from this region. Marker typing across the CLN1 region suggests that JNCL with GROD may be an allelic variant of infantile NCL. Show less