congenital myopathy 22B, severe fetal

Congenital myopathy 22B, severe fetal is a muscle disorder that presents with significant weakness and abnormal muscle development evident even before birth. It is associated with pathogenic variants in the SCN4A gene, which plays a role in muscle excitability. The condition typically manifests with decreased fetal movements and abnormal prenatal findings, followed by postnatal muscle weakness and motor delays. Precise prevalence estimates are not well established, and the severity of symptoms varies considerably among affected individuals.

The clinical presentation of this condition spans multiple systems, with early prenatal signs such as decreased fetal movement, polyhydramnios, and nonimmune hydrops fetalis suggesting a severe in utero onset. After birth, affected individuals often exhibit facial muscle weakness, a weak cry, and motor delays alongside hypotonia and generalized amyotrophy. Skeletal abnormalities, such as high palate, micrognathia, talipes, limb joint contractures, and hip contractures, are frequently observed, while respiratory challenges may be compounded by pulmonary hypoplasia. Not all individuals experience all features, and severity varies considerably.

This condition is caused by pathogenic variants in the SCN4A gene, which is important in regulating muscle cell function. It is inherited in an autosomal recessive manner, meaning that an affected individual has received one altered copy of the gene from each parent. In families where both parents are carriers, there is a 25% chance with each pregnancy that the child will be affected. Genetic counseling is recommended to help families understand the inheritance pattern and assess risks for future pregnancies.

Currently, management focuses on supportive care and symptom management, as there are no specific approved treatments for this condition. Treatment plans are tailored to the individual and typically involve a multidisciplinary team that provides ongoing surveillance to detect complications early. Supportive measures may include respiratory support, physical and occupational therapy, and careful monitoring of nutritional and orthopedic needs. Patients should discuss treatment options with their healthcare team, and genetic counseling is recommended to further explain the implications of the autosomal recessive inheritance pattern.

The long-term outlook for individuals with congenital myopathy 22B, severe fetal is variable, with outcomes depending on the severity of muscle involvement and associated complications. With current standards of care, many individuals receive supportive treatments that aim to improve quality of life, although the condition may lead to significant challenges in motor function and respiratory health. Outcomes described in medical literature continue to evolve as standards of care improve. Families are encouraged to engage with genetic counselors and specialist care centers to better understand potential trajectories and management strategies, as individual experiences differ significantly.