Genetic basis and phenotypic correlations of the neuronal ceroid lipofusinoses.

The neuronal ceroid lipofuscinoses (NCLs) are a group of inherited neurodegenerative disorders that mainly affect children and are grouped together by similar clinical features and the accumulation of autofluorescent storage material. More than a dozen genes containing nearly 400 mutations underlying human NCLs have been identified. Most of the mutations in these genes are associated with a typical disease phenotype, but some result in variable disease onset, severity and progression. There are still disease subgroups with unknown molecular genetic backgrounds. This article is part of a Special Issue entitled: The Neuronal Ceroid Lipofuscinoses or Batten Disease.

Human pathology in NCL.

In childhood the neuronal ceroid lipofuscinoses (NCL) are the most frequent lysosomal diseases and the most frequent neurodegenerative diseases but, in adulthood, they represent a small fraction among the neurodegenerative diseases. Their morphology is marked by: (i) loss of neurons, foremost in the cerebral and cerebellar cortices resulting in cerebral and cerebellar atrophy; (ii) an almost ubiquitous accumulation of lipopigments in nerve cells, but also in extracerebral tissues. Loss of cortical neurons is selective, indiscriminate depletion in early childhood forms occurring only at an advanced stage, whereas loss of neurons in subcortical grey-matter regions has not been quantitatively documented. Among the fourteen different forms of NCL described to date, CLN1 and CLN10 are marked by granular lipopigments, CLN2 by curvilinear profiles (CVPs), CLN3 by fingerprint profiles (FPPs), and other forms by a combination of these features. Among extracerebral tissues, lymphocytes, skin, rectum, skeletal muscle and, occasionally, conjunctiva are possible guiding targets for diagnostic identification, the precise type of NCL then requiring molecular analysis within the clinical and morphological context. Autosomal-recessive adult NCL has been linked molecularly to different childhood forms, i.e. CLN1, CLN5, and CLN6, whilst autosomal-dominant adult NCL, now designated as CLN4, is caused by a newly identified separate gene, DNAJC5. This article is part of a Special Issue entitled: The Neuronal Ceroid Lipofuscinoses or Batten Disease.