Malignant migrating partial seizures of infancy

Alternate names

Migrating partial epilepsy of infancy; Migrating partial seizures of infancy; MMPEI; MPEI; MPSI; Epilepsy of infancy with migrating focal seizures; Malignant migrating focal seizures of infancy; MMPSI; Early infantile epileptic encephalopathy 14; EIEE14; Malignant migrating partial epilepsy of infancy; Migrating partial seizures in infancy

Definition

Malignant migrating partial seizures of infancy (MMPSI) is a severe form of epilepsy, a condition characterized by recurrent seizures.

Epidemiology

MMPSI is a rare condition. Although its prevalence is unknown, approximately 100 cases have been described in the medical literature.

Cause

• The genetic cause of MMPSI is not fully known.
• Mutations in the KCNT1 gene have been found in several individuals with this condition and are the most common known cause of MMPSI.
• Mutations in other genes are also thought to be involved in the condition.
• The KCNT1 gene provides instructions for making a protein that forms potassium channels.
• Potassium channels, which transport positively charged atoms (ions) of potassium into and out of cells, play a key role in a cell's ability to generate and transmit electrical signals.
• Channels made with the KCNT1 protein are active in nerve cells (neurons) in the brain, where they transport potassium ions out of cells.
• This flow of ions is involved in generating currents to activate (excite) neurons and send signals in the brain.

Gene mutations

• KCNT1 gene mutations alter the KCNT1 protein.
• Electrical currents generated by potassium channels made with the altered KCNT1 protein are abnormally increased, which allows unregulated excitation of neurons in the brain.
• Seizures develop when neurons in the brain are abnormally excited. It is unclear why seizure activity can migrate in MMPSI.
• Repeated seizures in affected individuals contribute to the developmental delay that is characteristic of this condition.

Inheritance

Even when a genetic cause is identified, most cases of MMPSI occur sporadically in people with no family history of the condition.

Signs and symptoms

• In MMPSI, specifically, partial seizures generally begin shortly after birth and are often not responsive to treatment.
• Although the seizures may occur relatively infrequently in the beginning, within a few months the frequency increases drastically with some affected people experiencing clusters of 5 to 30 seizures several times per day.
• Signs and symptoms associated with these episodes vary based on which part of the brain is affected during a given seizure.
• Although the seizures associated with MMPSI do eventually become less frequent, the long-term consequences of the condition may include profound developmental delay, microcephaly (unusually small head size), intellectual disability and a shortened lifespan (many do not survive past infancy or early childhood).

Diagnosis

The diagnosis of KCNT1-related epilepsy is established in a proband with intractable epilepsy and identification of a heterozygous pathogenic variant in KCNT1 by molecular genetic testing.<ref>Gertler T, Bearden D, Bhattacharjee A, et al. KCNT1-Related Epilepsy. 2018 Sep 20. In: Adam MP, Ardinger HH, Pagon RA, et al., editors. GeneReviews® [Internet]. Seattle (WA): University of Washington, Seattle; 1993-2021. Available from: https://www.ncbi.nlm.nih.gov/books/NBK525917/</ref>[1].

Treatment

• Treatment is generally focused on minimizing recurrent seizures.
• Unfortunately, the seizures associated with MMPSI are usually not well-controlled with medications that are typically prescribed to treat epilepsy.

References

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NIH genetic and rare disease info

• NIH info on Malignant migrating partial seizures of infancy

Malignant migrating partial seizures of infancy is a rare disease.

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