progressive myoclonic epilepsy type 3

Progressive myoclonic epilepsy type 3 is a neurological disorder characterized by myoclonic seizures and other motor and cognitive challenges. It is caused by mutations in the KCTD7 gene and inherited in an autosomal recessive manner. Affected children typically experience a period of typical early development followed by emerging neurological symptoms. This condition is very rare, affecting fewer than 1 in 1,000,000 people.

Affected individuals commonly present with truncal ataxia and absent speech, which are considered hallmark features. After a period of apparently typical early development, affected children experience a phase of developmental regression marked by loss of previously acquired skills, alongside progressive psychomotor deterioration. Other frequently reported features include focal myoclonic seizures, myoclonus, dysarthria, and various types of seizures such as focal EEG discharges with secondary generalization and bilateral tonic-clonic seizures with focal onset. In addition, some individuals may experience intellectual disability, visual loss, and structural brain changes such as hypoplasia of the corpus callosum. Not all individuals experience all features, and severity varies considerably.

This condition is caused by pathogenic variants in the KCTD7 gene, which plays a role in normal neuronal function. It is inherited in an autosomal recessive pattern, meaning that an affected individual must inherit two copies of the mutated gene, one from each parent. Because it is more common when parents share a common ancestor, families with related parents may have a higher likelihood of both carrying the same rare variant. Genetic counseling is recommended for families to understand inheritance and discuss family planning options.

Currently, management focuses on supportive care and symptom management since there are no FDA-approved or foundational therapies specifically linked to this condition. Treatment is tailored to the individual and typically involves a multidisciplinary team to address neurological, motor, and developmental concerns. Regular surveillance is an essential part of long-term care, helping to identify potential complications early. Although there is an orphan drug designation under investigation, families are encouraged to discuss all treatment options with their healthcare team and consider genetic counseling for further guidance.

Progressive myoclonic epilepsy type 3 is a lifelong neurodevelopmental condition characterized by an initial regression followed by a period of relative stabilization and, in some individuals, later motor decline. Outcomes vary depending on symptom severity, age of diagnosis, and access to specialized care, and severity and symptoms vary widely between individuals. Outcomes described in medical literature continue to evolve as standards of care improve. Families often find it helpful to connect with specialists who are knowledgeable about this condition for ongoing support and guidance.

Clinical trials are underway exploring new treatment approaches for progressive myoclonic epilepsy type 3. Individuals interested in clinical trials can search ClinicalTrials.gov or consult their care team about eligibility.