Nemaline myopathy
| Nemaline myopathy | |
| ICD-10 | G71.2 |
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| ICD-9 | 359.0 |
| OMIM | 161800 256030 605355 |
| DiseasesDB | 31991 Template:DiseasesDB2 Template:DiseasesDB2 |
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Overview
Nemaline myopathy (also called rod myopathy or nemaline rod myopathy) is a group of congenital, hereditary neuromuscular disorders that cause muscle weakness, generally nonprogressive, of varying severity. "Myopathy" means "muscle disease," and a biopsy of muscle from a person with nemaline myopathy shows abnormal thread-like rods, called nemaline bodies, in the muscle cells. People with nemaline myopathy (or NM) usually experience delayed motor development and weakness in the arm, leg, trunk, throat, and face muscles. The disorder is often clinically categorized into several groups, including mild (typical), intermediate, severe, and adult-onset; however, these distinctions are somewhat ambiguous, as the categories frequently overlap. Respiratory problems are a primary concern for people with all forms of NM, and though in some severe cases they may threaten life expectancy, aggressive and proactive care allows most individuals to survive and lead active lives.
Nemaline myopathy is one of forty neuromuscular diseases covered by the Muscular Dystrophy Association.
Genetic qualities
Nemaline myopathy is a clinically and genetically heterogeneous disorder. Both autosomal dominant and autosomal recessive forms occur. Genetic mutations found to be responsible for the disorder include the alpha-actin gene, the nebulin gene, tropomyosin 2 gene, tropomyosin 3 gene, and troponin T. The physical capabilities of a given person with NM do not correlate well either with genotype or with muscle pathology as observed in the biopsy. [1]
History and early identification
"Rod myopathy" was first identified by Dr. Douglas Reye, an Australian physician, in 1958. However, Reye's results were never published because another doctor dismissed his finding of rods in the muscle tissue as an artifact of the biopsy. Forty years later, Reye's "rod myopathy" patient was confirmed to have nemaline myopathy. Another group of Australian researchers has since published an article recognizing Reye for his work. [2]
"Nemaline myopathy" was first named in a published paper in 1963 by North American researchers Cohen and Shy. Today, laboratories performing research on NM are located in the United States (Boston), Finland, and Australia.
Physical characteristics and effects
Physical expression of nemaline myopathy varies greatly, but weakness is usually concentrated in the proximal muscles, particularly respiratory, bulbar and trunk muscles. People with severe NM are usually obviously affected at birth, while those with intermediate or mild NM may initially appear unaffected. Babies with NM are frequently observed to be "floppy" and hypotonic. Children born with NM often gain strength as they grow, though the effect of muscle weakness on body features may become more evident with time. Adults with NM typically have a very slender physique.
Mobility and orthopedics
Most children with mild NM eventually walk independently, although often at a later age than their peers. Some use wheelchairs or other devices to enhance their mobility. Individuals with severe NM generally have limited limb movement and use wheelchairs fulltime.
Because of weakness in the trunk muscles, people with NM are prone to scoliosis, which usually develops in childhood and worsens during puberty. Many individuals with NM undergo spinal fusion surgery to straighten and stabilize their backs. Osteoporosis is also common in NM.
Respiratory involvement
Attention to respiratory issues is critical to the health of all people with NM. Infants with severe NM frequently experience respiratory distress at or soon after birth. Most are ventilated via tracheostomy, and with proper breathing assistance they may attain good health. Though respiratory compromise may not be immediately apparent in people with intermediate or mild NM, it nearly always exists to some extent. As in many neuromuscular disorders, hypoventilation can begin insidiously, and it may cause serious health problems if not remedied by the use of noninvasive mechanical devices to assist breathing, particularly at night. [3]
Communication and eating
Bulbar (throat) muscle weakness is a main feature of nemaline myopathy. Most individuals with severe NM are unable to swallow and receive their nutrition through feeding tubes. Most people with intermediate and mild NM take some or all of their nutrition orally. Bulbar muscle impairment may also lead to difficulty with communication. People with NM often have hypernasal speech as a result of poor closure of the velopharyngeal port (between the soft palate and the back of the throat). Communicative skills may be enhanced through speech therapy, oral prosthetic devices, surgery, and augmentative communication devices. Individuals with NM are usually highly sociable and intelligent, with a great desire to communicate.
Nemaline community
In 1999, the first non-medical webpage on nemaline myopathy was launched, and in October 2004, the first Nemaline Myopathy Convention was held in Toronto, Canada. A second convention is planned for the summer of 2007 in Edinburgh, Scotland. In March 2006, Niki Shisler released a book, Fragile, in which she recounted her experiences surrounding the birth of twin sons with severe NM.
External links
- Official Nemaline Myopathy website
- Nemaline Myopathy Foundation
- Muscular Dystrophy Association's (MDA) Information Page on Nemaline Myopathy
- A Washington University site delineating the various forms of NM
Template:Muscular Dystrophy Template:PNS diseases of the nervous system