Muscular diseases in babies are generally progressive. Babies may appear normal at birth but then are unable to meet expected milestones or regress in development. Muscular diseases can affect muscles that are vital for sustaining life.
Spinal Muscular Atrophy
Spinal muscular atrophy, a disorder that affects muscle movement, prevents babies from crawling, walking, sitting and moving their heads. The disease is caused by a loss of motor neurons, or nerve cells, in the spinal cord and the part of the brain known as the brain stem, which connects to the spinal cord, notes the U.S. National Library of Medicine's Genetics Home Reference website.
Four types of spinal muscular atrophy affect children before age 1. Type I, also known as Werdnig-Hoffman disease, appears at birth or within a few months, causing difficulty breathing and swallowing. Type II usually becomes apparent between 6 and 12 months of age. Babies with this type can sit without support but cannot stand without help. The third type, or X-linked spinal muscular atrophy, is similar to Type I but involves joint deformities, with some babies born with broken bones. Babies with the last type, known as distal spinal muscular atrophy Type 1, have progressive muscle weakness in the hands and feet that spreads to the extremities. Paralysis in the chest muscles and breathing failure eventually occurs.
Mutations in several genes cause these disorders, which affect 1 in 6,000 to 1 in 10,000 people, notes Genetics Home Reference. Management might include a permanent feeding tube, surgery for curvature of the spine and an artificial airway, or tracheostomy, for breathing problems. Life expectancy varies; some patients could have the same life expectancy as the general population.
Pompe Disease
Pompe disease is an inherited disease that results from a buildup of a sugar called glycogen in the baby's cells. The sugar builds in the muscles, causing the baby to have poor muscle tone and muscle weakness. Eventually, poor weight gain, heart and breathing problems develop. According to the Gene Reviews website, enzyme replacement therapy is necessary to prevent death from heart complications. Mutations in the GAA gene, which provides instructions for making the enzyme acid maltase, cause Pompe disease. If the disease is left untreated, death is likely within the first year.
Tay-Sachs
Tay-Sachs is a rare disease passed on to babies from parents who each carry a mutated HEXA gene. The HEXA gene provides instructions for making part of the enzyme that helps prevent toxic levels of a fatty substance from developing in the brain and spinal cord, notes the Genetics Home Reference website. Tay-Sachs becomes apparent when the baby starts to lose motor control and can no longer turn over, sit or crawl. As the disease worsens, seizures, vision and hearing loss, alterations in brain function and paralysis occur. Children usually live until early childhood. There is no cure for Tay-Sachs.
Canavan Disease
Canavan disease is a disorder caused by alterations in the ASPA gene, which provides instructions for an enzyme responsible for breaking down a substance found in nerve cells. Babies with this disorder initially appear normal, but by 3 to 5 months of age, they're no longer able to control their heads, turn over or sit up properly. According to the Genetics Home Reference website, this disease occurs among people of all ethnic backgrounds but is more common in those of Ashkenazi Jewish heritage. Some patients die in childhood; others live to adolescence or beyond.
References
- National Library of Medicine Genetics Home Reference: Spinal Muscular Atrophy
- National Library of Medicine Genetics Home Reference: Pompe Disease
- Gene Reviews: Glycogen Storage Disease Type II (Pompe Disease)
- National Library of Medicine Genetics Home Reference: Tay-Sachs disease
- MayoClinic.com: Tay-Sachs Disease
