Professionals

Clinical features
NEXMIF-encephalopathy (NEXMIF-E) is characterized by developmental delay/intellectual disability (ID), epilepsy in most affected individuals and an increased risk of autism and behavioral problems. Developmental delay precedes ID of various degree, ranging from mild to profound ID. Most patients develop epilepsy, which is typically a generalized epilepsy. Additional features are hypotonia, gastrointestinal problems, microcephaly, and growth retardation during childhood and overweight/obesity in adulthood.

A more extensive description of the clinical spectrum of NEXMIFmutations can be found in the section “Professionals – Clinical characteristics.” (link)

Prevalence
To date clinical information is available on approximately 90 individuals of which approximately 1 in 3 are males. It is likely more individuals will be diagnosed as genetic testing is more commonly used for undiagnosed intellectual disability and epileptic encephalopathies.

Inheritance
NEXMIF-E is an X-linked disorder with complete penetrance but variable expressivity in males, and incomplete penetrance and variable expressivity in females.

The pathogenic gene variant can be de novoin the patient (approximately 80 %) or maternally inherited.