Below is a general overview of the characteristics of the neuromuscular diseases that affect children and teens. The disorders are grouped into six categories. For more detailed information about a specific disease, check out the Muscular Dystrophy Association’s free “Facts About” disease booklets. The booklets are available online or through your local MDA office.

MUSCULAR DYSTROPHIES (involving the structure of the muscle cells)

BECKER (BMD) • Age of Onset: 2 to 16 years

Characteristics: A milder, more slowly progressing form of Duchenne MD (see below).

CONGENITAL (CMD) • Age of Onset: Birth

Characteristics: Generalized muscle weakness with possible joint deformities. Progresses very slowly.

Possible cognitive effects: Some of the most serious brain effects in neuromuscular diseases are found among people with CMD, although not everyone is affected. Children with structural brain abnormalities and those with seizures are most at risk for a wide range of problems, from learning disabilities, to vision and reading difficulties, to severe mental retardation.

DUCHENNE (DMD) • Age of Onset: 2 to 6 years

Characteristics: General muscle weakness and wasting, beginning in upper arms and legs and eventually involving all voluntary muscles. DMD affects mainly boys but in rare cases may affect girls, who have a slower and less severe progression.

Boys in the primary grades may run more slowly, have trouble walking long distances, difficulty climbing stairs and getting up from the floor. By age 10, boys are likely to be using a wheelchair at least part-time, and their arms are weakened. Around age 15, the arms, legs and torso all are affected and wheelchair use usually is full-time. The student may need help writing and lifting, and may show early signs of respiratory and heart weakness.

Possible cognitive effects: About a third of children with DMD have some degree of learning disability, especially in three areas: attention focusing, verbal learning and memory, and emotional interaction. Sometimes this impairment is mistaken for attention deficit disorder. DMD sometimes causes children to have poor social skills, be emotionally distant and moody, or inappropriately impulsive and lacking good social boundaries.

EMERY-DREIFUSS (EDMD) • Age of Onset: Childhood to early teens

Characteristics: Weakness and wasting of shoulder, upper arm and shin muscles. Joint deformities are common, and heart complications can be serious.

FACIOSCAPULOHUMERAL (FSH) • Age of Onset: Childhood to early adulthood

Characteristics: Childhood onset causes more severe symptoms than adult onset. Weakness and wasting affect face muscles, speech, eyelids, shoulders and upper arms. Progresses slowly with periods of rapid deterioration.

LIMB-GIRDLE (LGMD) • Age of Onset: Childhood to middle age

Characteristics: Muscle wasting begins in the shoulder and pelvic girdles. Scoliosis and heart-lung problems are common. Progression rate varies. Therapy helps maintain mobility and avoid respiratory illness.

MYOTONIC (MMD) (STEINERT’S DISEASE) • Age of Onset: Birth to early childhood

Characteristics: An inability to relax muscles (myotonia), combined with muscle weakness. Affects face, feet, hands and neck first. Progression is slow.

Possible cognitive effects: When MMD appears in infancy or childhood, about 75 percent of children have mental retardation, as well as severe facial weakness and speech abnormalities. Later-onset MMD (adolescence through adulthood) isn’t as closely associated with mental retardation, but may cause teens to be overly sleepy during the day and to lack initiative and seem apathetic.

Medication helps students stay more alert, as does addressing any underlying respiratory or heart problems.

PERIPHERAL MOTOR NEURON DISEASES (involving muscle-controlling nerve cells of the arms, legs, neck, face)

CHARCOT-MARIE-TOOTH (CMT) DISEASE • Age of Onset: Childhood to young adulthood

Characteristics: Weakness and atrophy of muscles and nerves of the arms from the elbows down and legs from the knees down. May involve foot deformities and some numbness. Ankle sprains are common. About 10 percent of children experience muscle cramping or burning nerve pain. Children may need leg braces, wrist braces and/or surgery, and may use a wheelchair for mobility.

DEJERINE-SOTTAS (DS) DISEASE • Age of Onset: Infancy

Characteristics: Slow development of early motor skills, leading often to loss of skill. Hands and legs are weak and may have impaired sensation. Severity and progression vary.

FRIEDREICH’S ATAXIA (FA) • Age of Onset: 7-13 years

Characteristics: Symptoms include shaky movements, lack of coordination, poor balance, slurred speech, muscle weakness and loss of sensation. Severity and progression vary. Often associated with diabetes and heart disease.

MOTOR NEURON DISEASES (involving nerve cells in the spinal cord)

INFANTILE PROGRESSIVE SPINAL MUSCULAR ATROPHY (SMA TYPE 1) • Age of Onset: Birth-6 months

Characteristics: Generalized muscle weakness, trouble swallowing and sucking, breathing distress, paralysis of legs and arms. Death often comes in very early childhood, but medical technology is expanding life span

INTERMEDIATE SMA (SMA TYPE 2) (WERDNIG-HOFFMAN DISEASE) • Age of Onset: 6 months-3 years

Characteristics: Weakness in arms, legs, upper and lower torso, often with skeletal deformities. Lung disease is common. Rapid progression. Survival into early adulthood is common but respiratory problems are a constant threat.

Possible Cognitive Effects: Although not scientifically validated, high intelligence often is noted in people with SMA.

JUVENILE SMA (SMA TYPE 3) (KUGELBERG-WELANDER DISEASE) • Age of Onset: 1-15 years

Characteristics: A milder form of intermediate SMA, with slower progression. Weakness in leg, hip, shoulder, arm and respiratory muscles. Calf muscles often are enlarged. A wheelchair may not be required in youth.

SPINAL-BULBAR MUSCULAR ATROPHY (SBMA) (KENNEDY’S DISEASE) • Age of Onset: 15-60 years

Characteristics: Occurs only in males, causing weakness in limbs and muscles involved in talking, chewing and swallowing. Some males experience breast enlargement. This disease progresses very slowly.

NEUROMUSCULAR JUNCTION DISEASES (involving the site where nerves and muscles meet)

CONGENITAL MYASTHENIC SYNDROME (CMS) (SOMETIMES DIAGNOSED AS MYASTHENIA GRAVIS) Age of Onset: Infancy to childhood

Characteristics: Generalized weakness and fatigability of voluntary muscles, including those controlling mobility, eye movement, swallowing and breathing. Rest can help restore strength. Varies in severity and weakness can fluctuate. May be controlled with medication.

MYOPATHIES (involving tone and contraction of muscles controlling voluntary movements; may include inflammation of muscles or related tissues)

CENTRAL CORE DISEASE • Age of Onset: Birth to infancy

Characteristics: Slow development of motor skills. Hip displacement common.

DERMATOMYOSITIS • Age of Onset: Childhood to age 60

Characteristics: Symptoms include skin rashes, muscle pain and tenderness, fever, gastrointestinal distress, and progressive weakness, especially affecting the shoulders, upper arms, hips, thighs and neck muscles. Swelling of the upper eyelids also is common. Hard painful nodules may appear under the skin. Progression and severity vary by individual. Corticosteroid drugs and restricted diet may result in remission.

HYPERTHYROID/HYPOTHYROID MYOPATHY • Age of Onset: Childhood to adulthood

Characteristics: Weakness in arms and legs. Stiffness and cramps common. Severity depends on success in treating underlying thyroid condition.

MYOTONIA CONGENITA (THOMSEN’S DISEASE) • Age of Onset: Infancy to childhood

Characteristics: Muscle stiffness and difficulty moving after periods of rest. With exercise, muscle strength and movement may return to normal.

MYOTUBULAR MYOPATHY (CENTRONUCLEAR MYOPATHY) • Age of Onset: Birth to infancy

Characteristics: Drooping of upper eyelids, facial weakness, foot drop and some weakness of the limbs and trunk. Individuals usually have no reflexes. Slow progression.

NEMALINE MYOPATHY (ROD BODY DISEASE) • Age of Onset: Birth to infancy

Characteristics: Low muscle tone and weakness of arms, legs, trunk, face and throat muscles. Severe cases have respiratory weakness.

PARAMYOTONIA CONGENITA • Age of Onset: Childhood to early adulthood

Characteristics: Muscle stiffness and difficulty relaxing muscles, especially after repeated use or exercise.

POLYMYOSITIS • Age of Onset: Childhood to age 60

Characteristics: Weakness of neck and throat, shoulder, hip and thigh muscles, and generalized muscle swelling. Swallowing difficulties are common. Severity and progression vary. Corticosteroid drugs may help.

METABOLIC DISEASES OF MUSCLE (involving errors in metabolism in producing energy in muscle cells)

ACID MALTASE DEFICIENCY (POMPE’S DISEASE) • Age of Onset: Infancy to adulthood

Characteristics: For infants, the disease is generalized and severe, impairing the heart and liver. Later-onset forms involve weakness of mid-body and respiratory muscles. Progression varies.

CARNITINE DEFICIENCY • Age of Onset: Early childhood

Characteristics: Varied weakness of shoulder, hip, face and neck muscles. Often occurs with other metabolic conditions. Progression varies. Carnitine supplementation can be effective.

DEBRANCHER ENZYME DEFICIENCY (CORI’S OR FORBES’ DISEASE) • Age of Onset: 1 year

Characteristics: General muscle weakness, poor muscle control and an enlarged liver with low blood sugar. Slow progression.

MITOCHONDRIAL MYOPATHY • Age of Onset: Early childhood to adulthood

Characteristics: Severe muscle weakness. Progression and severity vary. In some cases the brain is involved, causing seizures, deafness, loss of balance and vision, and mental retardation. Other systems in the body also can be affected.

Possible cognitive effects: Some children have impaired cognition, especially if they experience seizures, strokes or high levels of lactic acid in the blood. But others have high intelligence, such as the late MDA National Goodwill Ambassador Mattie J.T. Stepanek, who was a New York Times best-selling poet.

PHOSPHORYLASE DEFICIENCY (MCARDLE’S DISEASE)
PHOSPHOFRUCTOKINASE DEFICIENCY (TARUI’S DISEASE)
PHOSPHOGLYCERATE KINASE DEFICIENCY
PHOSPHOGLYCERATE MUTASE DEFICIENCY
LACTATE DEHYDROGENASE DEFICIENCY
Age of Onset: Childhood, adolescence or adulthood

Characteristics: Children with these disorders may not appear to be impaired until they exert themselves physically, and so often are unfairly thought to be lazy. These metabolic conditions cause a low tolerance for exercise, with symptoms including cramps, muscle pain and weakness, nausea, vomiting, muscle damage and discoloration of the urine (due to muscle breakdown).

Rest usually helps restore strength. Severity varies, increasing with age. Children often are advised to avoid strenuous exercise.