SNP Shot: Genomic Insights

Malignant migrating partial seizures of infancy (MMPSI) is a very severe type of epilepsy that starts in early infancy. Seizures that keep coming back begin before 6 months of age, often within just weeks after birth. These seizures are hard to treat effectively. While babies with MMPSI might initially develop normally, their progress stops and they lose skills once the seizures start. This leads to significant developmental delays.

The seizures in MMPSI are called partial, or focal, because they originate in specific areas of the brain instead of affecting the entire brain at once. The seizure activity might appear in different areas or move (migrate) around the brain during a single seizure. Depending on the brain region involved, the seizures can cause sudden redness and warmth (flushing) of the face, drooling, brief pauses in breathing (apnea), the head or eyes turning to one side, twitching of the eyelids or tongue, chewing motions, or jerking of an arm, leg, or both on one side of the body. If the seizure activity spreads to encompass the entire brain, it results in loss of consciousness, muscle stiffness, and rhythmic jerking movements (tonic-clonic seizure). These seizures that begin as partial seizures and then spread are called secondarily generalized seizures.

At first, the seizures linked to MMPSI happen infrequently, maybe every few weeks. However, within months of the seizures starting, they become much more frequent. Individuals with MMPSI can experience clusters of five to 30 seizures multiple times each day. Typically, each seizure lasts from seconds to a couple of minutes, but they can also be prolonged (classified as status epilepticus). In some cases, the seizure activity can be almost continuous for several days. After a year or more of ongoing seizures, the seizures tend to become less frequent.

Seizures can impair brain growth, potentially resulting in a smaller-than-normal head size (microcephaly). The problems with brain development can also lead to severe developmental delays and intellectual disability. Babies affected by MMPSI often lose the mental and physical abilities they had gained after birth, like making eye contact and controlling their head movements. Many have low muscle tone (hypotonia) and become "floppy." If the seizures can be managed for a short time, development may improve slightly. Some children with MMPSI may learn to reach for objects or walk. However, most children with this condition do not develop language skills.

Due to the serious health complications associated with MMPSI, many affected individuals do not live beyond infancy or early childhood.

Inheritance:

MMPSI is not passed down from parents and does not occur in families. It is caused by a new genetic change (mutation) that happens very early in the developing embryo (called a de novo mutation).