What is becker muscular dystrophy (BMD)?
Becker muscular dystrophy (BMD) is a hereditary muscle disorder in males, also called Becker muscular dystrophy or Becker dystrophy. Roughly speaking, it is a muscle disease resembling a Duchenne dystrophy (Duchenne muscular dystrophy), but usually is milder. Becker muscular dystrophy usually occurs later (on average around the 12th year of life, ranging between 5 and 30 years) and the muscle decline is slower than in Duchenne muscular dystrophy. However, there are also forms of BMD who have a severe course. The namesake, Dr. Peter Emil Becker, this syndrome in 1955, described for the first time.
Names
Apart from Becker's muscular dystrophy or Becker Dystrophy (muscle) are also other names used. Is wrongly used the name Becker disease, but this is another disease. The English name of the Becker's muscular dystrophy is BMD (Becker Muscular Dystrophy). In this review is further used the term BMD.
General
BMD is a hereditary neuromuscular disease transmitted belonging to the group of muscle diseases disorder. There is a sex-linked inheritance (boys get the disease, girls are bearer). The protein required for the structure and muscle dystrophin called defect resulting in an abnormal muscle: this gives muscular dystrophy. In Duchenne muscular dystrophy lack the dystrophin protein (practically) completely. Becker's muscular dystrophy affects 1 / 20,000 (figures from the Netherlands) for boys and Duchenne muscular dystrophy affects 1 / 4,000 boys
Becker muscular dystrophy symptoms
The first symptoms usually occur between the 10th and 20th year of life. These are for example muscle pain after minor exertion and recurrent. Sometimes a muscle decay arise some red urine (Myoglobinuria) can give. Furthermore, muscle cramps and muscle weakness (later symptom). Often these children are clumsy (especially waddling gait) and fall regularly. In the beginning it is very difficult to differentiate normal muscle pain, cramps or clumsiness. Especially the proximal muscles (near the trunk) are affected: thighs and upper arms. In addition to the ordinary muscles may also be affected the heart. For this, regular monitoring by a cardiologist is necessary. Becker muscular dystrophy gives very often in the long term degradation of the heart (cardiomyopathy: the dilated form). This indicates risk of heart failure and arrhythmias. Female carriers of the gene may also have symptoms such as muscle cramps and weakness (at about 20% of the carriers). Additionally occurs in about 15% degradation of the heart, carriers should therefore be regular monitoring of the heart. BMD can indicate malignant hyperthermia in general anesthesia, a life threatening condition. Patients with BMD should mention this at all operations to the doctor.
Backer muscular dystrophy diagnosis
The first indication is often obtained from the blood: the creatine kinase (CK) is extremely increased. The value amounts to several thousand (2000 to 12,000) instead of a maximum of 200. The main contribution to the diagnosis is the DNA research focused on muscular dystrophy. This research often takes several months and is carried in the LUMC (Leiden University Medical Center). Also, a muscle biopsy may be required (with a special staining for the dystrophin protein). Also is sometimes made an electromyogram (EMG). In female carriers is in about 30% of the cases an elevated creatine kinase present. There is also a standard cardiac ECHO and made an electrocardiogram (ECG).
Classification of muscular diseases
Becker muscular dystrophy is a muscle disease. BMD belongs to the group of muscle diseases in the narrower sense, as a subgroup of the muscular dystrophies (dystrophinopathies). The other muscle diseases peculiar to this subset of muscular dystrophies are Duchenne dystrophy (Duchenne muscular dystrophy); the oculopharyngeal dystrophy, limb-girdle muscular dystrophy and Facio-scapulo-humeral dystrophy (FSHD, disease Landouzy-Dejerine). The group of muscle diseases include in addition to the narrow sense dystrophies also myotonieën (eg Steinert's disease), and myopathies (such as Pompe disease).
Heredity
The disease is inherited through the sex or X-chromosome, which means that especially boys and girls get the disease its wearer. See also the section on genetics in Duchenne muscular dystrophy. In a third of the cases there is question of a new mutation (spontaneous mutation), wherein the disease is thus not previously occurred in the family. A boy with BMD can also pass on the disease: daughters are carriers, sons are healthy (for getting the father's Y). The abnormal gene (piece of genetic material, which takes care of the making of the dystrophin protein) sits on chromosome Xp2i. It is called the dystrophin gene. In Duchenne muscular dystrophy lacking the protein (almost) completely because the gene product delivers no. BMD at the protein is abnormal, but present. Sometimes the abnormal gene is not to prove with DNA testing, while it may have a BMD. A pregnancy of a mother who is a carrier prenatal diagnosis can be performed. It is possible with a flake test after about 11 weeks of gestation to demonstrate the defective gene with the aid of DNA analysis.
Becker muscular dystrophy treatment (Therapy)
There is no treatment to restore the cause (the defective dystrophin protein). In Duchenne muscular dystrophy is currently in patients (selected cases) to examine whether a protein absent a slightly defective protein can be made. A Duchenne may be a Becker. This technique is called exon skipping. So the treatment is symptomatic and aimed at complaints: tools like wheelchairs, rehabilitation, physiotherapy and the like. Furthermore, a cardiologist can possibly prescribe medication as directed the heart is affected. The effect of corticosteroids such as Prednisone is examined. There are many side effects that limit the use, benefit there has not been proven conclusively.
Course and prognosis
The disease becker muscular dystrophy is detected between 5 and 30 years (average age 12). Life expectancy is mainly determined by the severity of the affected his heart. The weakness sometimes gives respiratory problems in the very long term. In Duchenne play a much more prominent role breathing problems. There is a very varied course where they average around the age of 25 is in a wheelchair, but there are also cases of patients never become wheelchair dependent.