Autosomal dominant centronuclear myopathy

Alternate names

Autosomal dominant centronuclear myopathy

Definition

Autosomal dominant centronuclear myopathy (AD-CNM) is a type of centronuclear myopathy, which is a group of rare, inherited conditions that affect the muscles.

Epidemiology

Centronuclear myopathy is a rare condition; its exact prevalence is unknown.

Cause

Most cases of AD-CNM are caused by changes (mutations) in the DNM2 gene; however, some affected families are reported to have mutations in the MYF6 or CCDC78 genes.

Inheritance

Autosomal dominant pattern, a 50/50 chance.

The condition is inherited in an autosomal dominant manner.

Signs and symptoms

n AD-CNM, specifically, the severity of the condition and the associated signs and symptoms vary significantly among affected people. In people with a mild form, features of the condition generally don't develop until adolescence or early adulthood and may include slowly progressive muscle weakness, muscle pain with exercise and difficulty walking. Although some affected people will eventually lose the ability to walk, this usually does not occur before the 6th decade of life. In more severe cases, affected people may develop symptoms during infancy or early childhood such as hypotonia and generalized weakness. These children generally have delayed motor milestones and often need wheelchair assistance in childhood or adolescence.

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

• Centrally nucleated skeletal muscle fibers

30%-79% of people have these symptoms

• Abnormality of the foot musculature(Abnormal foot muscles)
• Decreased fetal movement(Less than 10 fetal movements in 12 hours)
• Delayed gross motor development(Delayed motor skills)
• Difficulty walking(Difficulty in walking)
• EMG: myopathic abnormalities
• Generalized hypotonia(Decreased muscle tone)
• Large for gestational age(Birth weight > 90th percentile)
• Macrocephaly at birth(Big skull present at birth)
• Mildly elevated creatine kinase
• Muscle fibrillation
• Polyhydramnios(High levels of amniotic fluid)
• Proximal muscle weakness in lower limbs
• Proximal muscle weakness in upper limbs
• Ptosis(Drooping upper eyelid)
• Spontaneous abortion
• Thin ribs(Slender ribs)
• Type 1 muscle fiber predominance

5%-29% of people have these symptoms

• Areflexia of lower limbs
• Calf muscle hypertrophy(Increased size of calf muscles)
• Cavernous hemangioma(Collection of dilated blood vessels that forms mass)
• Cryptorchidism(Undescended testes)
• Exercise-induced myalgia(Exercise-induced muscle pain)
• External ophthalmoplegia(Paralysis or weakness of muscles within or surrounding outer part of eye)
• Neonatal asphyxia
• Peripheral axonal neuropathy
• Pyloric stenosis
• Respiratory insufficiency due to muscle weakness(Decreased lung function due to weak breathing muscles)
• Skeletal muscle hypertrophy(Increased skeletal muscle cells)
• Urinary incontinence(Loss of bladder control)

1%-4% of people have these symptoms

• Malignant hyperthermia

Diagnosis

Molecular Genetics Tests may includeː

• Deletion/duplication analysis
• Sequence analysis of the entire coding region
• Mutation scanning of the entire coding region
• Targeted variant analysis

Treatment

Treatment is based on the signs and symptoms present in each person and may include physical and/or occupational therapy and assistive devices to help with mobility, eating and/or breathing.

NIH genetic and rare disease info

• NIH info on Autosomal dominant centronuclear myopathy

Autosomal dominant centronuclear myopathy is a rare disease.

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