Infantile neuroaxonal dystrophy
Infantile neuroaxonal dystrophy is a rare, progressive disorder that primarily affects the nervous system, leading to developmental regression and movement difficulties.
Overview
Infantile neuroaxonal dystrophy is a disorder that primarily affects the nervous system. While individuals typically appear healthy at birth, they begin to experience delays in motor and intellectual skills between 6 and 18 months of age, eventually losing previously acquired skills (developmental regression).
Symptoms
- Movement: Muscles are initially weak and "floppy" (hypotonic) before becoming very stiff (spastic). Eventually, children lose the ability to move independently.
- Feeding and breathing: Muscle weakness leads to feeding difficulties and breathing problems, which can cause frequent infections like pneumonia.
- Vision and hearing: Rapid, involuntary eye movements (nystagmus), eyes that do not look in the same direction (strabismus), and vision loss due to optic nerve atrophy. Hearing loss may also occur.
- Cognitive: Progressive deterioration of cognitive functions (dementia) and loss of awareness of surroundings. Seizures occur in some children.
Causes
Most cases are caused by mutations in the PLA2G6 gene, which provides instructions for an enzyme called A2 phospholipase. This enzyme is involved in breaking down fats called phospholipids, which are crucial for maintaining cell membranes. Impaired function of this enzyme may disrupt cell membrane maintenance and lead to the development of swellings called spheroid bodies in the axons of nerve cells. The exact link between these cellular changes and the clinical symptoms remains under study.
Inheritance
This condition is inherited in an autosomal recessive pattern. Both copies of the gene in each cell must have mutations to cause the disorder. Parents of an affected individual typically carry one copy of the mutated gene without showing symptoms.