developmental delay and seizures with or without movement abnormalities

Developmental delay and seizures with or without movement abnormalities (DEDSM) is a neurodevelopmental disorder that primarily affects brain function, leading to delays in development and early-onset seizures with a myoclonic component. This condition is linked to alterations in the DHDDS gene, and it is inherited in an autosomal dominant manner. Affected individuals typically present in early childhood with a variety of neurological symptoms and movement abnormalities such as ataxia, dystonia, and tremor. Although precise prevalence data is not available, the variability in presentation means that not every person experiences every feature.

Individuals with DEDSM commonly exhibit global developmental delay and epileptic encephalopathy, with early-onset seizures that may include generalized myoclonic, bilateral tonic-clonic, and myoclonic absence types. They may also demonstrate variable intellectual disability and present with hypotonia during infancy. Movement abnormalities such as ataxia, tremor, and other abnormal movements including dystonia are frequently observed. Not all individuals experience all features, and severity varies considerably.

DEDSM is caused by pathogenic variants in the DHDDS gene. The protein produced by DHDDS plays an important role in cellular processes that affect neurological development, and disruptions in its function are linked with the neurological and movement abnormalities seen in affected individuals. This condition is inherited in an autosomal dominant pattern, meaning that a single altered copy of the gene can lead to the disorder. That even within the same family, the severity and specific symptoms can vary considerably, reflecting both variable expressivity and incomplete penetrance.

Currently, management focuses on supportive care and symptom management, as there are no treatments specifically approved for this condition. Treatment is tailored to the individual and typically involves a multidisciplinary team that may include neurology specialists, physical and occupational therapists, and other professionals experienced in managing neurodevelopmental disorders. Genetic counseling is recommended to help families understand the inheritance pattern and to guide family planning decisions. Patients should discuss treatment options with their healthcare team to determine which therapies may be most appropriate for their situation.

The clinical course of developmental delay and seizures with or without movement abnormalities is variable, with outcomes differing widely between individuals. With current standards of care, many affected individuals are able to manage their symptoms into adulthood, although the overall trajectory may include periods of stabilization and changes in motor function over time. Outcomes described in medical literature continue to evolve as standards of care improve, and the degree of functional impact depends on the severity of symptoms and access to specialized care. Families often find it helpful to connect with genetic counselors and support groups for additional guidance and assistance in navigating the condition.