SNP Shot: Genomic Insights

STAC3 disorder, previously known as Native American myopathy, is a condition primarily affecting the skeletal muscles, the muscles responsible for body movement. Individuals with this disorder exhibit muscle weakness (myopathy) and reduced muscle tone (hypotonia) affecting the entire body, typically evident from birth.

The muscle weakness associated with STAC3 disorder contributes to many of its defining characteristics. Infants may experience difficulties with feeding and swallowing. Delays in motor skill development, such as sitting, crawling, standing, and walking, are common. Many individuals develop characteristic facial features described as "myopathic facies," which can include drooping eyelids (ptosis), sunken cheeks, and a mouth that is often open with downward-turned corners. Other facial features that may be present include a small lower jaw (micrognathia), a cleft palate, low-set ears that slant backward, smaller or downward-slanting eye openings (short or downslanting palpebral fissures), or an increased distance between the inner corners of the eyes (ocular telecanthus).

Individuals with STAC3 disorder may also be born with joint contractures, limiting movement, or develop scoliosis or kyphosis, which are abnormal curvatures of the spine. When these occur together, it is often referred to as kyphoscoliosis. Affected individuals often exhibit shorter stature compared to their peers and family members.

A significant concern for individuals with STAC3 disorder is an elevated risk of malignant hyperthermia, a severe reaction to certain anesthetics and muscle relaxants used during surgery and other invasive procedures. Exposure to these triggering drugs can lead to muscle rigidity, muscle fiber breakdown (rhabdomyolysis), high fever (hyperthermia), elevated acid levels in the body (acidosis), and a rapid heart rate. Untreated malignant hyperthermia can be life-threatening, emphasizing the importance of prompt drug discontinuation and symptom management.

Inheritance:

STAC3 disorder follows an autosomal recessive inheritance pattern. This means that a person 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 carriers.