Ullrich CMD
Clinical characteristics of Ullrich CMD (or Ullrich’s disease) include hypotonia (loss of muscle tone), hyperlaxity (loose joints) in the hands and feet, and multiple joint contractures at birth, with rigidity of the spine. The course is slowly progressive, causing muscle weakness and wasting. Intelligence is normal. Children with Ullrich’s disease may develop respiratory failure during sleep in the first decade of life.
Research
http://www.mda.org/research/070417cmd_cyclosporine-like_compound.html
Bethlem myopathy
This rare form of CMD is, like Ullrich’s, caused by a lack of collagen, but it has a less severe course. It can first appear at any age, and features restricted joint mobility, including finger contractures. (It’s called a myopathy, which means “muscle disease,” a broader term than dystrophy, which implies progressive degeneration.)
Emery-Dreifuss muscular dystrophy
Emery-Dreifuss muscular dystrophy is characterized by wasting and weakness of the muscles that make up the shoulders and upper arms and those of the calf muscles of the legs. Another prominent aspect of this disease is the appearance of contractures (stiff joints) in the elbows, neck and heels very early in the course of the disease. Finally, and very importantly, a type of heart problem called a conduction block is a common feature of EDMD and requires monitoring.
Researchers recently have identified the genes that, when defective, lead to the forms of EDMD. We now know that the gene that’s defective in X-linked EDMD makes a small protein called emerin, which normally is located in the membrane that surrounds each cell’s nucleus (the compartment in a cell’s center that contains the chromosomes).
It isn’t yet understood how the loss of emerin from the nuclear membrane in X-linked EDMD leads to the symptoms of muscular dystrophy. Some researchers think this lack of emerin interferes with the reorganization of the nuclear membrane after a cell has divided, leading to weak or dying cells. Along these same lines, the gene that’s been found defective in both the autosomal and recessive forms of EDMD contains the instructions for two closely related proteins called lamin A and lamin C that also are associated with the nuclear membrane of cells.
Again, it isn’t yet known how changes
in lamins A and C lead to the symptoms of muscular dystrophy, but
some research suggests that the nuclear membrane may become
destabilized when the lamin proteins are abnormal. This could lead
to muscle breakdown.
The symptoms of EDMD usually become apparent by 10 years of age, but the disorder tends to progress slowly. Early signs include “toe-walking” because of stiff Achilles’ tendons in the heels, and difficulty bending the elbows. Later the signs of muscle weakness become more prominent but are still generally considered mild. Usually cardiac problems are detectable by age 20, but they can occur at earlier stages in the disease as well. Intellect isn’t affected.
The contractures that occur early in EDMD may make arm, neck, heel and spine movements difficult; however, the progression of muscle weakness seems to occur very slowly in EDMD and may not become a source of difficulty until later in life. Cardiac problems can be life-threatening and may require the insertion of a pacemaker or treatment with medications.
Research - http://www.mdaquest-digital.com/mdaquest/20070102/?pg=24
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