5q14.3 microdeletion syndrome

5q14.3 microdeletion syndrome (also known as MEF2C haploinsufficiency syndrome or 5q14.3 deletion syndrome) is a rare chromosomal disorder caused by a deletion on the long arm of chromosome 5 at position 14.3, which typically encompasses the MEF2C gene. This gene plays a critical role in brain development, neuronal differentiation, and synaptic function. The syndrome primarily affects the central nervous system and is characterized by severe intellectual disability, absent or very limited speech, epilepsy (often with onset in early childhood), and stereotypic movements. Affected individuals frequently display hypotonia (low muscle tone) in infancy, which may evolve into hypertonia or spasticity over time. Additional clinical features commonly include hyperkinetic movements, repetitive hand movements or hand-wringing (sometimes resembling Rett syndrome), limited or absent ambulation, and a generally happy or sociable demeanor. Craniofacial features may include a broad forehead, flat nasal bridge, upturned nose, and widely spaced eyes, though these can be subtle. Brain MRI may show abnormalities such as delayed myelination, thin corpus callosum, or cerebral atrophy. Some patients also experience feeding difficulties, gastroesophageal reflux, and visual impairment. Most cases arise de novo (as new mutations not inherited from parents), though the condition follows an autosomal dominant pattern of inheritance since loss of one copy of MEF2C is sufficient to cause disease. There is currently no cure or disease-specific treatment for 5q14.3 microdeletion syndrome. Management is supportive and symptomatic, including antiepileptic medications for seizure control, physical therapy, occupational therapy, speech therapy, and orthopedic interventions as needed. Early intervention programs are recommended to optimize developmental outcomes.

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