SNP Shot: Genomic Insights

Riboflavin transporter deficiency neuronopathy is a neurological disorder affecting nerve cells (neurons). Individuals with this condition commonly experience hearing loss due to nerve damage in the inner ear, known as sensorineural hearing loss, along with other signs of nerve damage.

Beyond the inner ear, this condition affects nerves in the brainstem, the area connecting the brain to the spinal cord, particularly the pontobulbar region. Damage to these nerves leads to pontobulbar palsy, characterized by paralysis of the muscles they control. Because the pontobulbar region controls vital voluntary muscle functions like breathing, speech, and limb movement, individuals with riboflavin transporter deficiency neuronopathy may experience breathing difficulties, slurred speech, and muscle weakness in the face, neck, shoulders, and limbs. Muscle stiffness (spasticity) and exaggerated reflexes are also common.

The onset of riboflavin transporter deficiency neuronopathy varies, ranging from infancy to young adulthood. Infants often present with life-threatening breathing problems as the initial symptom due to nerve damage. In children and young adults, sensorineural hearing loss typically appears first, followed by signs of pontobulbar palsy.

Without treatment, the symptoms of riboflavin transporter deficiency neuronopathy progressively worsen. Severe respiratory problems and infections are frequently the cause of death. Untreated infants typically survive less than a year, while individuals developing the condition after age 4 often survive for more than a decade.

Riboflavin transporter deficiency neuronopathy includes what were previously classified as two separate disorders: Brown-Vialetto-Van Laere syndrome (BVVLS) and Fazio-Londe disease. These conditions share similar symptoms; however, Fazio-Londe disease does not involve sensorineural hearing loss. Due to their shared genetic cause and overlapping symptoms, they are now recognized as variations of the same underlying disorder.

Inheritance:

Riboflavin transporter deficiency neuronopathy is generally inherited in an autosomal recessive manner. This means that an individual must inherit two copies of the mutated gene, one from each parent, to develop the condition. Parents who each carry one copy of the mutated gene are typically asymptomatic, meaning they don't show signs or symptoms of the disorder.