Sandhoff Disease
Description
Sandhoff disease, also known as hexosaminidase A and B deficiency, is a rare, inherited disorder that primarily affects the nervous system. It is characterized by the accumulation of a fatty substance called GM2 ganglioside in the brain and spinal cord. This buildup disrupts normal brain function, leading to severe neurological problems. This blog post explores the intricacies of Sandhoff disease, delving into its causes, symptoms, diagnosis, management, and ways to thrive with this condition.
Genes Involved
Sandhoff disease is caused by mutations in the HEXB gene, located on chromosome 5. This gene provides instructions for making a protein called beta-hexosaminidase B, an enzyme essential for breaking down GM2 ganglioside. Mutations in HEXB lead to a lack of functional beta-hexosaminidase B, resulting in the accumulation of GM2 ganglioside in the brain and spinal cord.
Recognizing the Signs and Symptoms
Sandhoff disease typically manifests in infancy with symptoms like:
- Delayed development: Infants may miss developmental milestones like rolling over, sitting up, or crawling.
- Seizures: Recurrent seizures can occur.
- Muscle weakness and loss of muscle control: This can lead to difficulty moving and holding up the head.
- Vision loss: The eyes may exhibit a cherry-red spot on the retina, a characteristic sign.
- Hearing loss: Hearing problems can occur.
- Mental retardation: Cognitive impairment and developmental delays are common.
- Feeding difficulties: Issues with swallowing and sucking can arise.
- Breathing problems: Respiratory issues are possible.
As Sandhoff disease progresses, individuals may experience:
- Paralysis: Loss of muscle function can lead to paralysis.
- Spasticity: Tightening of muscles.
- Blindness: Vision loss can become complete.
- Death: Most individuals with Sandhoff disease sadly do not live beyond childhood.
Causes
Sandhoff disease is an inherited disorder, meaning it is passed down from parents to children. Both parents must carry the mutated HEXB gene for a child to inherit the disease. If both parents are carriers, there is a 25% chance for each pregnancy that their child will inherit Sandhoff disease.
Inheritance/recurrence risk
Sandhoff disease follows an autosomal recessive inheritance pattern. This means that an individual must inherit two copies of the mutated gene, one from each parent, to develop the disorder. If both parents are carriers of the mutated gene, there is a 25% chance for each pregnancy that their child will inherit Sandhoff disease. The other possibilities are a 25% chance of the child inheriting two normal copies of the gene, a 50% chance of the child inheriting one normal and one mutated copy (making them a carrier but not having the disease).
