Centronuclear Myopathy
(1 in 50,000 to 100,000 births)
X-Linked Myotubular Myopathy (Myotubularin)- MTM1
Autosomal Dominant Centronuclear Myopathy (Dynamin 2) -DNM2
Autosomal Recessive Centronuclear Myopathy (Amphiphysin 2) - BIN1
Autosomal Dominant or Recessive Centronuclear Myopathy (Ryanodine Receptor 1) - RYR1
Autosomal Recessive Titin Disorders (Titin) - TTN
Autosomal Recessive Centronuclear Myopathy with striated muscle preferentially expressed protein kinase) - SPEG
Classic Severe Form:
Extreme muscle weakness and hypotonia is seen from birth which can cause respiratory distress and feeding difficulties. Some babies at their severest will have no ability to suck, swallow or breath and will require ventilation from infancy which has its own dangers including recurrent infections, inadequate shallow breathing and hypoxia. Some children will only last a few months or a year, but some can survive longer requiring 24 hour ventilator support, feeding support and wheelchairs. The least severe may be able to be fully independent of the ventilator or be capable of taking breaks from it except for during sleep.
Cognitive functioning is not effected with this illness unless it is secondary to an extreme hypoxic event. Most children will be non-ambulatory since there is poor muscle development. Sometimes a freeform halo will be used so that a child can still looking around and be upright even with lack of full muscle control in their neck. The disease is not believed to be progressive, but the development of the muscles is so poor to begin with that it causes issues regardless. There has also been shown that children with this disorder are more easily fatigued then their peers.
There are some distinctive features to these children including facial features such as a high forehead, mid-face hypoplasia, weak facial muscles and a long face with a disproportionately long and harrow head. They also tend to unnaturally tall in comparison to their peers and have macrocephally. Some other characteristics may include a narrow high arched palate, severe misalignment of teeth, inability to fully control eye movements, drooping of upper eyelids, nearsightedness, and undescended testes. As they grow older their fingers and toes my appear abnormally long and contractures will occur. They also will deal with possible fractures of long bones, hip dysplasia and scoliosis. Some will also deal with peliosis hepatitis, which can cause the liver to hemorrhage.
Mild/Moderate Form (about 10 to 5% of all cases):
Those with the moderate form will follow the course of the severe form only they will have longer time before being ventilated and possibly longer periods before they become fully ventilator dependent. They also may obtain some motor milestones such as using a gait trainer or walker and not requiring reliance fully on a wheelchair. Those with the mild form may only require ventilator support as an infant and most will achieve the ability to walk unaided. They tend to not have the common facial features of those with the severest form, but more commonly are effected by paralysis of the eye muscles. Both versions can lead to sleep apnea and nocturnal hypoventiliation. Illnesses also can cause issues with breathing and these all may lead to ventilator support temporarily or only during sleep.
Treatment
At the moment treatment is done via occupational and physical therapy to help with any possible muscle development and to stop contractures. There also is communication support to help with communication while ventilator dependent. There are gene therapies being researched but they are not approved as an alternative therapy at this time.
