Tay-Sachs Disease, Infantile Type (TSD) is a rare, inherited disorder that progressively destroys nerve cells (neurons) in the brain and spinal cord. This disease occurs when the body lacks an enzyme called b-hexosaminidase A (HexA), which acts as a catalyst to help break down a chemical found in nerve tissue called ganglioside. Without this enzyme, gangliosides, and ganglioside GM2, build up in tissues and nerve cells in the brain. Mutations in the HEXA gene cause TSD, and infantile type TSD is the most common form. Infants with this disorder typically appear normal early in life, but after 6 months their development slows and the muscles used for motor skills such as turning over, sitting, and crawling deteriorate. Affected infants also develop an exaggerated startle reaction to loud noises. As the disease progresses, children with infantile TSD experience seizures, vision and hearing loss, intellectual disability and paralysis. Signs and symptoms of this disease includes: deafness, decreased eye contact, loss of muscle strength, delays of mental and social skills, progressive loss of cognitive and intellectual function (dementia), increased startle reaction, irritability, listlessness, loss of motor skills, paralysis, seizures, and slow growth. Children with infantile TSD often develop cherry red spots behind the retina, which is associated with gradual loss of vision.
DIAGNOSTIC TESTING, PHYSICAL FINDINGS, AND ICD-9-CM CODING
Definitive diagnosis: Chromosomal analysis showing mutations in the HEXA gene of chromosome 15.
Physical Findings: Low muscle tone; eye examination may reveal a cherry-red spot in the macula; and occasional macrocephaly.
ICD- 9: 330.1
Infantile TSD meets listing severity; Juvenile -onset and adult-onset TSD have later onset and more variable course, and should be evaluated under the affected body systems (Special Senses, Neurological, Mental).