SNP Shot: Genomic Insights

Adenylosuccinate lyase deficiency is a neurological condition impacting brain function (encephalopathy). This results in delays in mental and motor skill development (psychomotor delay), features similar to autism spectrum disorder impacting communication and social skills, and seizures. The presence of succinylaminoimidazole carboxamide riboside (SAICAr) and succinyladenosine (S-Ado) in bodily fluids is a crucial indicator aiding in the diagnosis of this disorder.

Adenylosuccinate lyase deficiency is categorized into three types based on the severity of symptoms. The neonatal form is the most severe. This form's symptoms can be identified at or before birth, including restricted growth during pregnancy and a smaller than normal head (microcephaly). Newborns with this form exhibit severe encephalopathy, which can manifest as lack of movement, feeding difficulties, and dangerous breathing problems. Certain babies may experience seizures that do not respond to treatment. Due to the severity of encephalopathy, infants with this form generally survive only a few weeks after birth.

Adenylosuccinate lyase deficiency type I (the severe form) is the most frequently seen. Symptoms appear in the early months of life. Affected infants experience significant psychomotor delay, low muscle tone (hypotonia), and microcephaly. Many infants develop recurring, difficult-to-treat seizures, and some display autistic behaviors, such as repetitive movements and avoiding eye contact.

In individuals with adenylosuccinate lyase deficiency type II (the moderate or mild form), initial development is usually normal for the first few years, followed by a slowing down. Psychomotor delay ranges from mild to moderate. Some children may develop seizures and autistic traits.

Inheritance:

This condition is inherited in an autosomal recessive manner. This means that both copies of the responsible gene in each cell have mutations. Individuals affected by this condition inherit one mutated gene copy from each parent. While the parents carry the mutated gene, they typically do not exhibit any symptoms of the condition.