|
MD subtype
|
Abbreviation
|
Affected protein(s)
|
Prevalence per 100,000
|
|
Becker Muscular Dystrophy
|
BMD
|
Dystrophin
|
1.6
|
|
Congenital Muscular Dystrophy
|
CMD
|
Collagen VI
Fukutin
Integrin-alpha7
Laminin
Selenoprotein
|
2.5
|
|
Distal Muscular Dystrophy
|
Distal MD
|
Dysferlin
Titin
|
10
|
|
Duchenne Muscular Dystrophy
|
DMD
|
Dystrophin
|
30
|
|
Emery-Dreifuss Muscular Dystrophy
|
EDMD
|
Emerin
Lamin
|
|
|
Facioscapulohumeral Muscular Dystrophy
|
FSHMD
|
Not known
|
0.8
|
|
Limb-Girdle Muscular Dystrophy
|
LGMD
|
Calpain3
Caveolin3
Dysferlin
Lamin
Myotilin
Sarcoglycan
Telethonin
Titin
|
0.8
|
|
Myotonic Muscular Dystrophy
|
MMD
|
Myotonin
|
12
|
|
Oculopharyngeal Muscular Dystrophy
|
OPMD
|
PABP2
|
?
|
DMD occurs due to the mutation in a gene
named Dystrophin (the largest gene identified in human)
resulting in deficiency of the muscle protein called dystrophin. A complex of
proteins, of which dystrophin is part, work together as an anchor and connects
muscle cell's cytoskeleton (structural framework) with the extracellular matrix
(lattice of protein molecules outside the cell). Any defect in dystrophin
protein compromises the complex from maintaining the structure of skeletal,
cardiac and other muscles. Therefore DMD and BMD patients display symptoms distinct for this deficiency. Similarly, defects
in proteins listed as 'affected proteins' in the table manifest in various
symptoms enabling categorization of subtypes in MD. In a scale of MD severity
due to dystrophin protein, DMD occupies the severe end of the MD spectrum while
the BMD occupies the other end.
MD is a multi-system disorder showing
manifestations in organ systems including heart, nervous systems, endocrine
glands (ductless glands), digestive system, eyes, skin and other organs.
Weakness and wasting (atrophy) of various voluntary
muscles of the body are clinical hallmarks of MD. Depending on MD subtype the disorders affect
different sets of muscles and have different
disease onset ages, severity and patterns of inheritance. MD is a progressive
disorder and most affected individuals require a wheelchair by mid teenage
years.
Elevated levels of serum enzyme creatine kinase (CK; also
called creatine phosphokinase) is an indication of MD. In
conditions such as MD where cellular membrane integrity is compromised, this
intracellular enzyme leaks from muscle fibers into blood circulation. In BMD and
DMD, CK levels are extremely high compared to normal subjects. Electromyography (EMG;
measures muscle electrical potential) using needle electrode is an invasive
method (a needle is inserted into the muscle) employed in suspected MD cases,
usually when CK level is not significantly elevated. EMG results on MD patients
display reduction in amplitude and duration of motor unit potential. EMG also
helps to rule out nervous system cause of the muscle weakness. Muscle histology
and immunocytochemistry (certain tissue staining tests done under
microscope) methods are also used in diagnosis. In cases where these diagnostic
methods are not definitive molecular genetic analysis might
help in diagnosis.
Prolonged immobilization in MD patients hasten
deterioration of muscles. Physiotherapy, physical exercise and being ambulatory
help ameliorate MD. Glucocorticoids, a kind of steroid, is used in certain type
of MD which prolongs the mobility of MD subjects for about two years. However
prolonged steroid administration has several severe side effects. Gene therapy
or stem-cell therapy are still in experimental stage and might help in MD
subjects in future. Presently no cure for MD is available.
Certain MD subtypes have localized geographic
distribution: Fukuyama-type CMD in Japan, Distal MD
is most common in Scandinavia, particularly Finland, OPMD in French regions of
Canada.
MD in the context of
India.
DMD/BMD and LGMD
are frequently reported MD cases compared to other subtypes in India.
Interestingly, in Britain, people of Indian ethnic background has been identified to have a
disproportionately high incidence of DMD compared to Pakistani or other ethnic
groups. In contrast, an observation in eastern India (Bihar, West Bengal and
Bangladesh) reports a higher incidence
of the DMD cases in Muslims compared to Hindu
population in that region. However, both these studies recognize paucity in
their patient sample size and resulting inability to arrive at a sensible statistical conclusion. A
separate report in 1997 'estimated' that there were about 22,000 DMD cases
present in India, and more than 2500 cases added every year. There are several
published reports on MD subtypes in recent years in India. A comprehensive
analysis of these reports, if initiated, might shed some light on true
prevalence of MD or MD subtypes in India and the subcontinent as well.
Contributor:
Duraiswamy Navaneetham PhD.
Temple University School of Medicine
Philadelphia, PA, USA
Reviewer: Ahmad Syed
MD, PhD.
Temple University School of Medicine,
Philadelphia, USA.
Oct. 2009.
1
Commonly cited by most MD
researchers, this estimate is from an exhaustive survey on the basis of
published MD reports from countries essentially in Europe and North America. Outside this core domain, Israel, Japan and Libya are the only countries
represented in this study. Interested readers may refer to:
Emery AEH,
Population frequencies of inherited neuromuscular diseases - A world survey.
Neuromuscular Disorders, 1991;
1:19.
2
Data collected
from various published reports on MD are shown. Numbers for MD subtypes other than DMD are
based on limited studies and may not be conclusive.
Related organizations in India
Muscular Dystrophy Association India
C/O V.J.Clinic,
New no: 6, (Old 21), Fourth Cross Street,
Sastri Nagar, Adyar
Chennai 600 020, Tamilnadu
Phone: 91-90032 95482
Email: mdaindia.org@gmail.com
http://www.mdaindia.org
Sundaram Medical Foundation
A Network Center of the Cooperative International
Neuromuscular Research Group
Shanthi Colony, 4th Ave.
Anna Nagar, Chennai 600 040,
Tamilnadu
Phone: 91-44-26268844
Muscular Dystrophy Foundation India
C/o.
People's Watch,
No.6,
Vallabhai Road,
Chokkikulam, Madurai-625 002, Tamilnadu
Phone:
91-9994368550
Indian Association of Muscular Dystrophy (IAMD)
President IAMD
C/O M/s Stich-n-Style
Hospital Road, Solan 173 212,
Himachal Pradesh
Phone: 91-1792-223183 / 220212
Email: info@iamd.org
http://www.iamd.org/
All India Muscular Dystrophy Association
Anaj Mandi, Nabha Gate
Patiala 147 001, Punjab
Phone: 91-175-2215786
Email: contact@mdaindia.com
http://www.mdaindia.com/
Indian Muscular Dystrophy Society
16, Tolaknagar
Paldi, Ahmedabad 380007, Gujarat
http://imdsindia.org/
Indian Muscular Dystrophy Association
M.I.G.72, APHB Colony,
Machilipatnam 521 001, Andhra Pradesh
Phone: 91-086-722817
