NEMALINE MYOPATHY
By Stacy A. Cossette, M.S.
EVER HEARD OF NEMALINE MYOPATHY?
If you are like most people, including health-care workers, the answer is “No, what’s nemaline myopathy?” Nemaline myopathy (NM) is a rareneuromuscular disease recognized by the Muscular Dystrophy Association that affects skeletal muscles as well as muscles used for eating, speaking, and breathing. The spectrum is wide, from a severe neonatal form that is incompatible with life, to a form so mild it is unrecognized until years or decades after birth.
DIAGNOSIS
Nemaline means ‘thread-like’ and myopathy means ‘muscle disease’. The diagnosis is based on muscle weakness, combined with the appearance of nemaline bodies within the muscle fiber on biopsy.
RESPIRATORY INVOLVEMENT
The muscles used for breathing are always affected in congenital NM and life-threatening breathing difficulties can occur. Infants with severe NM frequently experience respiratory distress at or soon after birth. Many are ventilated via tracheostomy (a direct airway through the throat). Though respiratory compromise may not be apparent in those with intermediate or mild NM, it usually exists to some extent. Individuals with all forms of NMcan experience frequent respiratory infections.
EATING, COMMUNICATION, COGNITION
Individuals with severe NM are unable to swallow and receive their nutrition through feeding tubes. Most with intermediate and mild NM take some or all of their nutrition orally. Diaphragm, throat, mouth, and facial muscle weakness may also lead to difficulty with speaking. Articulation is less precise, speech volume is lower, and some speech sounds may be impossible to produce, like /g/ and /k/, making their speech less intelligible.Speech may be enhanced through therapy, oral prosthetic devices, or surgery, with measurable gains likely. Individuals with NM are often highly intelligent.
STRENGTH AND MOBILITY
Many people with NM are able to walk, although some children begin walking later. Some may require wheelchair assistance, even if ambulatory,when prolonged standing or walking is required. Individuals with severe NM use wheelchairs fulltime. Children born with less severe forms of NM might achieve modest gains in strength over time through physical therapy. During growth spurts, the bones lengthen too rapidly for the muscles to keep up and there often is a decline in strength and physical ability.
SPINAL INVOLVEMENT
Because of weakness in the trunk muscles, people with NM are prone to scoliosis, a sideways curvature of the spine, which can develop in earlychildhood and worsens during puberty. Some individuals with NM undergo spinal fusion surgery to straighten and stabilize their backs.
GENETICS
Mutations in at least seven genes can cause Nemaline myopathy. These genes provide instructions for producing proteins, so when the instructions are wrong, the protein is flawed or missing. Defects in any one of these proteins inhibit muscle contraction and result in muscle weakness and dysfunction.
INCIDENCE
It is difficult to estimate the incidence of Nemaline myopathy due to its rarity, high probability of misdiagnosis and unidentified cases, and lack of reporting.
FOR MORE INFORMATION
Email: stacycossette@yahoo.com
http://www.davidmcd.btinternet.co.uk
http://www.buildingstrength.org/
