This is an extremely rare form of NCL and only a small number of cases with NCL have been written about. There may be more undiagnosed cases.
What is the cause? The disease is caused by mutations in a gene called KCTD7 which is also referred to as CLN14. CLN14 disease is inherited as an autosomal recessive disorder, which means that both copies of the CLN14 gene carry mutations in an affected individual and both parents are unaffected carriers. The gene CLN14 normally directs the production of a protein in the cell called KCTD7, which is the 7th member of a family of proteins containing the potassium (K) channel (C) tetramerization (T) domain (D) (hence the name KCTD7). If this protein is not produced, symptoms start in the first year of life. If some working protein is produced, symptoms may develop later and disease progression is slower.
How is it diagnosed? The diagnosis is usually made by genetic (CLN14) tests on blood samples looking for changes in all the genes known to cause epilepsy. Occasionally a skin biopsy may be taken to look for storage material in cells. Fingerprint-like profiles or granular deposits are the characteristic storage body at the electron microscope level.
How does the disease progress? Genotype/phenotype correlations Mutations in KCTD7 generally cause infantile progressive myoclonic epilepsy (PME) or an opsoclonus-myoclonus ataxia-like syndrome, neither of which affect vision or cause NCL disease-like storage. When visual failure and NCL-like storage is also present in cells of patients, the disease can be diagnosed as an NCL or CLN14 disease, which has epilepsy, motor and speech regression and visual failure.