A family of disorders, some of which are
fatal, some
not. All involve the
progressive weakening and
wasting of muscle tissue; this process is not painful by itself, but can have side-effects which are painful. There's
no cure, and patients don't recover muscle they've lost. The disorder is due to irregular or absent production of the
protein dystrophin, which is required for healthy
muscles. Depending on the form of
MD one has, the
symptoms can appear early or late in life, and can cause anything from mild
inconvenience to
severe disability and death.
The poster children for the Muscular Dystrophy Association (MDA) often have the more severe forms of MD. Since most people's image of the diseases comes from "Jerry's kids", most people think of MD as a death sentence or a ticket to a life that's unimaginably impaired; this picture is not entirely accurate. Some forms of MD do cause very severe disability and early death; death usually happens because the heart or lung muscles are affected. But many people with MD are quite mobile and lead pretty normal lives, with some degree of increase in daily engineering challenges. Most forms of MD don't affect mental function at all, although they may cause slurring of speech which is sometimes incorrectly interpreted as a sign of diminished mental capacity.
Muscular dystrophies are genetic; they are not contagious or a result of bad parenting. There may be environmental triggers for some forms of MD; in rare cases, a random genetic mutation can cause a child to develop MD even if its parents don't have the gene for MD. Scientists have identified the inheritance characteristics of most forms of MD, and in some cases, have identified a gene or genes which are thought to be responsible.
Muscular Dystrophies-- I've tried to include information on age of onset, primary effects, severity, incidence, and genetic profile. If the info isn't here, I couldn't find it. If there's no number given for the incidence, assume that the disorder is rare. These are in alphabetical order, except that Duchenne's is first.
Duchenne Muscular Dystrophy
(Also known as Pseudohypertrophic) --- Onset in early childhood, progresses slowly but affects all voluntary muscles including the lungs, generally fatal by 20s. It is inheritable, an x-linked recessive trait so it nearly always affects males. The involved gene has been identified, and in utero genetic tests for Duchenne's are very accurate. This is the most severe, and also one of the two most common forms of MD, striking about 1 in 4000 boys in the US.
Becker Muscular Dystrophy
Similar to Duchenne's but less severe. Onset in teens or 20s, progresses slowly but affects all voluntary muscles including the lungs, survival into 40s. It is an x-linked recessive trait so it nearly always affects males; the involved gene has been identified and there is an in utero test for it. It strikes about 1 in 25,000 in the US.
Congenital Muscular Dystrophy
Onset at birth. Weakens all muscles, may cause joint deformities. Fukuyama form is more severe and involves mental functions. Different forms have different inheritance characteristics; the involved gene has been identified for one form.
Distal Muscular Dystrophy
(Also Miyoshi) -- Onset in middle age. Affects muscles of hands, forearms, and lower legs. Slow progression, not life-threatening. It is autosomal dominant, so affects males and females equally.
Emery-Dreifuss Muscular Dystrophy
Onset in childhood or early teens, affects shoulder, upper arm, shin and heart muscles, may cause joint deformities. It is an x-linked recessive trait; the involved gene has been identified.
Facioscapulohumeral Muscular Dystrophy
(Also known as Landouzy-Dejerine) -- Onset from childhood to early adulthood. Affects facial muscles, upper arms and shoulders. Progresses slowly with periods of rapid deterioration; although much less severe than most forms of MD, it is tremendously variable in its degree of severity. Not life-threatening. It is autosomal dominant, so affects males and females equally. 1 out of 20,000 people have it.
Limb-Girdle Muscular Dystrophy
Onset anywhere from late childhood to middle age, affects the shoulder and pelvic girdles. There are at least 12 different forms, which differ in their genetic characteristics; involved genes have been identified for only some of these.
Myotonic Dystrophy
(Also known as Steinert's Disease) -- Onset anywhere from birth to middle age. Affects face, feet, hands and neck first, causing delayed relaxation of muscles after contraction (eg, inability to release grip on an object). Slow progression can span 60 years. It is autosomal dominant so affects males and females equally; the involved gene has been identified. Affecting 1 in 8000 people, it is the one of the two most common MDs.
Oculopharyngeal Muscular Dystrophy
Onset in early 20s to middle age. Affects muscles of eyelids and throat, swallowing problems commonplace as disease progresses. It is autosomal dominant, so affects males and females equally.
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Other disorders that aren't muscular dystrophies, but are commonly confused with MD. All affect motor control, but they do so by affecting the nervous system's ability to control muscles; they don't attack the muscles themselves:
ALS -- Lou Gehrig's disease -- This is what Stephen Hawking has.
MS -- Multiple Sclerosis
Myasthenia Gravis
Parkinson's Disease
Cerebral Palsy
Primary source of profiles of the different MDs: www.mdausa.org; some material in the profiles is quoted directly. The web sites of the Muscular Dystrophy Association (MDA) are the best starting place for more information; they have different sites in different countries.