SNP Shot: Genomic Insights

Spinal muscular atrophy with respiratory distress type 1 (SMARD1) is a genetic disorder characterized by muscle weakness and respiratory failure, typically starting in infancy. Common early signs include labored and noisy breathing, particularly during inhalation, a faint cry, feeding difficulties, and repeated bouts of pneumonia. Between 6 weeks and 6 months of age, infants with SMARD1 often experience sudden respiratory arrest due to paralysis of the diaphragm, the muscle responsible for lung expansion during breathing. This paralysis necessitates lifelong mechanical ventilation. In rare cases, the onset of SMARD1 symptoms occurs later in childhood.

Following respiratory failure, individuals with SMARD1 develop weakness in the distal muscles, those located further from the body's core, such as in the hands and feet. This weakness progresses to affect all muscles, generally stabilizing within two years. The extent of muscle function retained varies; some maintain limited movement, while others experience complete paralysis. This muscle weakness significantly hinders motor development, impacting the ability to sit, stand, and walk. Kyphoscoliosis, a combined abnormal curvature of the spine (scoliosis and kyphosis), can also develop. After the first year of life, deep tendon reflexes may diminish.

Additional characteristics of SMARD1 can include decreased pain perception, excessive sweating (hyperhidrosis), loss of control over bladder and bowel function, and an irregular heart rhythm (arrhythmia).

Inheritance:

SMARD1 follows an autosomal recessive inheritance pattern. This means that both copies of the gene responsible for the condition must have mutations for an individual to be affected. Individuals with one mutated copy of the gene are carriers and typically do not exhibit any signs or symptoms of the disorder; parents are almost always carriers.