Neuronal Ceroid Lipofuscinoses type 7 (NCL7), or CLN7 disease, is a rare neurodegenerative disorder within the Batten disease group. It is characterized by the abnormal accumulation of lipopigments in the nervous system's cells. Mutations in the MFSD8 gene cause CLN7 disease.
Neuronal ceroid lipofuscinoses type 7 genetic testing is included in Diagnostiki Athinon Monogenic Diseases Genetic Testing along with approximately 100 other inherited diseases, including cystic fibrosis (71 mutations) and hereditary breast cancer (genes BRCA1 415 mutations & BRCA2 419 mutations).
Critical features of neuronal ceroid lipofuscinoses type 7 (CLN7 disease) include:
- Onset: CLN7 disease typically begins in childhood, with the initial symptoms presenting between the ages of 2 and 7.
- Cognitive Decline: Progressive decline in cognitive abilities occurs, leading to intellectual disability.
- Motor Dysfunction: Individuals with CLN7 disease experience a gradual decline in motor skills, including coordination and balance.
- Seizures: Seizures are a common feature and may be one of the early signs of the condition.
- Visual Impairment: Vision loss is a characteristic feature, and affected individuals may experience difficulty with visual tasks.
- Speech and Language Regression: Speech and language skills loss may occur over time.
- Behavioral Changes: Changes in behavior, including irritability and aggression, may be observed.
- Movement Abnormalities: Some individuals may develop movement abnormalities such as tremors and myoclonic jerks.
- Brain Atrophy: Imaging studies may reveal progressive brain atrophy.
- Autosomal Recessive Inheritance: CLN7 disease follows an autosomal recessive inheritance pattern, meaning that affected individuals inherit mutated MFSD8 genes from both parents.
The MFSD8 gene provides instructions for making a protein involved in lysosomal function. Lysosomes are cellular structures responsible for breaking down and recycling various substances. Mutations in the MFSD8 gene result in impaired lysosomal function, accumulating lipopigments, and subsequent cell damage in the nervous system.
There is currently no cure for CLN7 disease, and management is primarily supportive, focusing on symptom relief and improving the quality of life for affected individuals. Seizures may be treated with antiepileptic medications, and other supportive measures, such as physical and occupational therapy, may be employed.
Genetic counseling is essential for families affected by CLN7 disease to understand the inheritance pattern, assess the risk of having affected children, and discuss available reproductive options. Due to the progressive and debilitating nature of the condition, early diagnosis is crucial for initiating appropriate supportive care and interventions.
More Information
Neuronal ceroid lipofuscinosis type 7 is an ultra-rare disease caused by mutations in the MFSD8 (or CLN7) gene, which codes for a lysosomal transmembrane transporter protein whose function is unknown. About 50 pathogenic variants have been described in MFSD8 that can cause this type of lipofuscinosis in homozygosis and compound heterozygosis. Individuals carrying one copy of a mutation in MFSD8 do not develop the disease but can transmit the mutation to their offspring.
Persons carrying one copy of a mutation in MFSD8 do not develop the disease but can transmit it to their offspring.
The c.362A>G (p.Tyr121Cys) mutation in exon 5 of the MFSD8 gene has been observed in patients in the homozygous state. This mutation is a nonconservative amino acid substitution that affects the secondary structure of the protein.
Neuronal ceroid lipofuscinoses type 7 genetic testing analyzes the 6 most frequent pathogenic mutations of the MFSD8 gene.
The technique used for genetic testing analyzes only the gene's specific mutations, which are the most important and frequent in the literature. However, it should be noted that there are likely other gene or chromosomal mutations in the gene to be tested that cannot be identified with this method. Different analysis techniques can be used for these cases, such as next-generation sequencing (NGS).
