Intermediate congenital nemaline myopathy

Alternate names

Intermediate congenital NM; Intermediate nemaline myopathy

Definition

Intermediate nemaline myopathy is a type of nemaline myopathy that shows features of typical NM in neonates with a more severe progression.

Epidemiology

The annual incidence of NM has been estimated at 1/50,000 live births, and intermediate NM might represent 20% of all cases.

Cause

The ACTA1 (1q42.13), NEB (2q22) or TPM3 (1q21.2) genes have been associated with intermediate NM.

Inheritance

The transmission pattern of the disease is autosomal recessive or dominant.

Signs and symptoms

• Neonates with intermediate NM present with spontaneous anti-gravity movements and active respiratory muscles, but with a progressive generalized weakness which prevents achievement of gross motor milestones or leads to loss of ambulation and/or independent respiration by age 11 years.
• Children often develop joint contractures.

Clinical presentation

For most diseases, symptoms will vary from person to person. People with the same disease may not have all the symptoms listed. 80%-99% of people have these symptoms

• Generalized muscle weakness
• Nemaline bodies
• Severe muscular hypotonia(Severely decreased muscle tone)

30%-79% of people have these symptoms

• Abnormal thorax morphology(Abnormality of the chest)
• Decreased fetal movement(Less than 10 fetal movements in 12 hours)
• Difficulty walking(Difficulty in walking)
• Dysphagia(Poor swallowing)
• EMG: myopathic abnormalities
• Hypokinesia(Decreased muscle movement)
• Hyporeflexia(Decreased reflex response)
• Motor delay
• Multiple prenatal fractures(Multiple fractures present at birth)
• Myopathic facies
• Polyhydramnios(High levels of amniotic fluid)
• Respiratory failure
• Skeletal muscle atrophy(Muscle degeneration)
• Type 1 muscle fiber predominance

5%-29% of people have these symptoms

• Areflexia(Absent tendon reflexes)
• Facial diplegia
• High, narrow palate(Narrow, high-arched roof of mouth)
• Hypertelorism(Wide-set eyes)
• Long philtrum
• Low-set ears(Low set ears)
• Ophthalmoplegia(Eye muscle paralysis)
• Premature birth(Premature delivery of affected infants)

1%-4% of people have these symptoms

• Arthrogryposis multiplex congenita

NIH genetic and rare disease info

• NIH info on Intermediate congenital nemaline myopathy

Intermediate congenital nemaline myopathy is a rare disease.