Neuronal Ceroid-Lipofuscinoses type 6 (associated to CLN6)
The neuronal ceroid-lipofuscinoses (NCLs) are a group of inherited, neurodegenerative, lysosomal storage disorders characterized by progressive intellectual and motor deterioration, seizures, and early death. Visual loss is a feature of most forms. Clinical phenotypes have been characterized traditionally according to the age of onset and order of appearance of clinical features into infantile, late-infantile, juvenile and adult.
Pathogenic variants in thirteen genes — PPT1, TPP1, CLN3, CLN5, CLN6, MFSD8, CLN8, CTSD, DNAJC5, CTSF, ATP13A2, GRN, KCTD7 — are known to cause NCL. The diagnosis of an NCL is increasingly based on assay of enzyme activity and molecular genetic testing. In unusual cases diagnosis relies on electron microscopy (EM) of biopsied tissues. The diagnostic testing strategy in a proband depends on the age of onset.
The NCLs are inherited in an autosomal recessive manner with the exception of adult onset, which can be inherited in either an autosomal recessive or an autosomal dominant manner. The most prevalent NCLs are CLN3 disease, classic juvenile and CLN2 disease, classic late infantile (although prevalence varies by ethnicity and country of family origin)
The first presenting symptom may vary among NCL phenotypes, which are typically distinguished on the basis of age of onset and clinical manifestations. Unusual pathogenic variants in many, if not all, NCL-associated genes may result in a milder or more severe disease phenotype.
Treatment is currently symptomatic and palliative only. Seizures, malnutrition, gastroesophageal reflux, pneumonia, sialorrhea, depression and anxiety, spasticity, Parkinsonian symptoms, and dystonia can be effectively managed.