Severe congenital nemaline myopathy

Alternate names

Severe congenital nemaline myopathy; Severe congenital (neonatal) NM

Definition

Severe congenital nemaline myopathy is a severe form of nemaline myopathy (NM) characterized by severe hypotonia with little spontaneous movement in neonates.

Epidemiology

The annual incidence of NM has been estimated at 1/50,000 live births and the severe congenital form might represent 10-20% of all cases.

Cause

The ACTA1 (1q42.13) and NEB (2q22) genes are associated with this form of NM.

Inheritance

Autosomal recessive inheritance, a 25% chance

NM is transmitted in an autosomal recessive fashion or occurs sporadically.

Signs and symptoms

• Neonates have sucking and swallowing difficulties, and gastroesophageal reflux, which leads to failure to thrive.
• Involvement of diaphragm and intercostal muscles contributes to respiratory insufficiency.
• Cardiomyopathy and arthrogryposis may occur.
• Survival after infancy is rare.

For most diseases, symptoms will vary from person to person. People with the same disease may not have all the symptoms listed. 30%-79% of people have these symptoms

• Axial muscle weakness
• Breech presentation(Feet or buttocks of fetus positioned near opening of uterus)
• Decreased fetal movement(Less than 10 fetal movements in 12 hours)
• Dysphagia(Poor swallowing)
• Hypokinesia(Decreased muscle movement)
• Increased connective tissue
• Motor delay
• Multiple prenatal fractures(Multiple fractures present at birth)
• Nemaline bodies
• Polyhydramnios(High levels of amniotic fluid)
• Respiratory failure
• Severe muscular hypotonia(Severely decreased muscle tone)
• Skeletal muscle atrophy(Muscle degeneration)
• Type 1 muscle fiber predominance

5%-29% of people have these symptoms

• Abnormality of the diaphragm(Diaphragm issues)
• Adducted thumb(Inward turned thumb)
• Arthrogryposis multiplex congenita
• Edema of the dorsum of hands
• Facial diplegia
• Hypospadias
• Large fontanelles(Wide fontanelles)
• Low-set ears(Low set ears)
• Micropenis(Short penis)
• Ophthalmoplegia(Eye muscle paralysis)
• Premature birth(Premature delivery of affected infants)
• Pulmonary hypoplasia(Small lung)
• Thin ribs(Slender ribs)

NIH genetic and rare disease info

• NIH info on Severe congenital nemaline myopathy

Severe congenital nemaline myopathy is a rare disease.

Resources

Frequently asked questions

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