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Becker Muscular Dystrophy

BMD

Becker muscular dystrophy (BMD) is an X-linked recessive inherited disorder characterized by progressive muscle wasting and weakness.


Presentation

The symptoms usually occur in childhood by 11 years of age. These children at first may appear clumsy and later may be diagnosed as suffering from Becker muscular dystrophy.

The symptoms of Becker muscular dystrophy include delayed gross motor milestones for example late walking, running, jumping and difficulty in climbing stairs. The gait can be affected leading to toe-walking gait. The weakness leads to increased number of falls and difficulty in rising from the floor. The lower limbs are more severely affected than the upper limbs with symmetrical, proximal weakness.

Gower’s sign is seen in muscular dystrophies. It manifests such the patient has to use his hands and arms to walk up his own body from a squatting position due to lack of hip and thigh muscle strength. Subclinical Becker muscular dystrophy might occur with atypical presentations like focal myopathy, cramping during exercise and isolated cardiomyopathy.

There may be joint contractures; for example of the Achilles tendon or at the elbow. Also, pseudohypertrophy of the calves is observed. There are cases of patients presenting without weakness but with symptoms of dilated cardiomyopathy. The disease eventually causes the patient to become dependent on the wheelchair.

The complications of Becker muscular dystrophy include progressive weakness which can cause joint deformities and medical emergencies for cardiac and respiratory symptoms.

Progressive disability, dialted cardiomyopathy, scoliosis, dysphagia, joint contractures, functional constipation and a need for ventilator support even may occur in the long run. The complications due to being wheelchair bound include restricted respiratory activity due to inter-coastal and diaphragm weakness.

Difficulty Walking
  • walking with wheelchair needed at approximately 12 years and breathing difficulties and heart disease by age 20 years.[ltd.aruplab.com]
  • Muscle weakness of the lower body, including the legs and pelvis area, slowly gets worse, causing: Difficulty walking that gets worse over time; by age 25 to 30, the person is usually unable to walk Frequent falls Difficulty getting up from the floor[nlm.nih.gov]
  • It primarily affects males. 0012086 Difficulty climbing stairs Difficulty walking up stairs 0003551 Difficulty walking Difficulty in walking 0002355 Elevated serum creatine kinase Elevated blood creatine phosphokinase Elevated circulating creatine phosphokinase[rarediseases.info.nih.gov]
  • Becker's muscular dystrophy Neurology An X-linked condition characterized by slowly progressive muscle weakness of the legs and pelvis, difficulty walking, mental retardation, fatigue and pseudohypertrophy of calf muscles[medical-dictionary.thefreedictionary.com]
  • In some, they may appear later than this By the age of around 25-30 years, a majority of individuals have difficulty walking and ultimately lose their ability to walk.[dovemed.com]
Difficulty Climbing Stairs
  • As the condition progresses, muscle weakness leads to functional difficulties (difficulty climbing stairs or rising from a chair).[orpha.net]
  • Abstract: Case report regarding a 23 year old gentleman, presented with difficulty climbing stairs, changes in posture and toe walking. Significant calf hypertrophy was seen on examination.[um.edu.mt]
  • Complaints might include difficulties using the arms above shoulder height, or difficulty climbing stairs, running, or getting out of low chairs. Such weakness can come on at any age. If it does develop it will slowly worsen with time.[dfsg.org.uk]
Wheelchair Bound
  • Two patients became wheelchair bound in their 40s or beyond, while the other 2 (aged 73 and 69, respectively) were still able to walk at the time of examination.[ncbi.nlm.nih.gov]
  • The complications due to being wheelchair bound include restricted respiratory activity due to inter-coastal and diaphragm weakness.[symptoma.com]
  • The early clinical course in BMD is milder than that in DMD, and patients become wheelchair-bound at age sixteen or older.[clinicaladvisor.com]
  • Patients are often wheelchair-bound by age 12 Becker is characterized by later-onset skeletal muscle weakness Patients remain ambulatory into their 20s Despite milder skeletal muscle involvement, heart failure from dilated cardiomyopathy is a common cause[en.wikibooks.org]
Pediatric Disorder
  • Little is known about parental motivations and expectations for clinical trials for rare pediatric disorders.[ncbi.nlm.nih.gov]
  • Unfortunately, one challenge will be for adult care providers to take on patients with Duchenne or Becker muscular dystrophy as this is historically considered a pediatric disorder and few patients with Duchenne muscular dystrophy survive into adulthood[emedicine.medscape.com]
Vietnamese
  • The largest deletion database of the dystrophin gene, established in Vietnamese DMD/BMD patients, disclosed a strong indication for exon-skipping therapy.[ncbi.nlm.nih.gov]
  • In a 22-year-old Vietnamese male with BMD, cardiac involvement became apparent at age 19 years with reduced systolic function, which was treated with ramipril.[ncbi.nlm.nih.gov]
Pulmonary Disorder
  • The pulmonologist will deal with pulmonary disorders arising due to the muscle weakness and breathing restriction. Orthopedicians will be able to provide relief in the scoliosis that might occur at later age.[symptoma.com]
Severe Clinical Course
  • Although they have a severe clinical course, a positive dystrophin immunofluorescence pattern was seen using C-terminal antibody, and a dystrophin band of reduced molecular weight (corresponding to their DNA deletions), but which maintained the C-terminus[ncbi.nlm.nih.gov]
Myopathy
  • A modern diagnostic approach to myopathies should, therefore, not only include morphological and biochemical investigations, but also be extended to the analysis of the dystrophin gene.[ncbi.nlm.nih.gov]
  • From Wikidata Jump to navigation Jump to search X-linked recessive inherited disorder characterized by slowly progressive muscle weakness of the legs and pelvis Benign pseudohypertrophic muscular dystrophy benign congenital myopathy Becker's muscular[wikidata.org]
  • INTRODUCTION: Quantitative MRI techniques detect disease progression in myopathies more sensitively than muscle function measures or conventional MRI.[ncbi.nlm.nih.gov]
  • Recognizing these features is important for differentiating it from other myopathies that may have similar features and avoids unnecessary invasive procedures such as muscle biopsy. 2015 Wiley Periodicals, Inc.[ncbi.nlm.nih.gov]
  • His mother experienced walking difficulties from 35 years of age and has a myopathy with marked calf hypertrophy, a raised CK, and a myopathic muscle biopsy. Dystrophin analysis was undertaken on both the proband and his mother.[ncbi.nlm.nih.gov]
Muscular Atrophy
  • BACKGROUND/PURPOSE: The purpose of this study was to explore the prevalence, nature and scope of pain in adolescents with spinal muscular atrophy and Duchenne and Becker muscular dystrophy and whether the pain differs between diagnostic groups or between[ncbi.nlm.nih.gov]
  • Two other patients with a deletion of exon 47 showed progressive muscular atrophy and weakness; they were considered to be typical BMD in both clinical features and the type of gene deletion.[ncbi.nlm.nih.gov]
  • We assessed the level and factors that affect parent attitudes regarding NBS panel inclusion of Duchenne muscular dystrophy (DMD), Becker muscular dystrophy (BMD), and spinal muscular atrophy (SMA).[ncbi.nlm.nih.gov]
  • ., Duchenne/Becker muscular dystrophy (DMD/BMD), myotonic dystrophy type 1 (DM1), spinal muscular atrophy (SMA).[ncbi.nlm.nih.gov]
  • Duchenne's muscular dystrophy ( Duchenne type muscular dystrophy ) The childhood type of muscular dystrophy. myotonic dystrophy a rare, slowly progressive, hereditary disease, marked by myotonia followed by muscular atrophy (especially of the face and[medical-dictionary.thefreedictionary.com]
Pseudohypertrophy of Calf Muscles
  • Becker's muscular dystrophy Neurology An X-linked condition characterized by slowly progressive muscle weakness of the legs and pelvis, difficulty walking, mental retardation, fatigue and pseudohypertrophy of calf muscles[medical-dictionary.thefreedictionary.com]
  • ) in calf muscles Muscle wasting that begins in the legs and pelvis, then progresses to the muscles of the shoulders, neck, arms, and respiratory system Laboratory tests that help confirm the diagnosis include: [3] CPK Electromyography ( EMG ) Muscle[rarediseases.info.nih.gov]
  • ” of calf muscles.[clinicaladvisor.com]
Gowers Sign
  • From age 27 years, he developed proximal muscle weakness predominantly of the lower limbs, a positive Gower sign, and a waddling gait.[ncbi.nlm.nih.gov]
  • The doctor will check for the Gower sign.[aapmr.org]
  • Affected individuals typically have pseudohypertrophy of the calf muscles and exhibit toe-walking, waddling gait, and the Gower sign (climbing up the legs when rising from a seated position on the floor).[mayomedicallaboratories.com]
  • Gower’s sign is seen in muscular dystrophies. It manifests such the patient has to use his hands and arms to walk up his own body from a squatting position due to lack of hip and thigh muscle strength.[symptoma.com]
  • Physical See the list below: The Gower sign is not a specific finding for muscular dystrophy, but it does point to proximal weakness in the hip extensors, leading to the pattern of movement seen when patients rise from the floor.[emedicine.medscape.com]
Neglect
  • Parents of patients with DMD reported higher burden than those of patients with BMD, especially concerning feeling of loss (84.3% DMD vs. 57.4% BMD), stigma (44.2% DMD vs. 5.5% BMD) and neglect of hobbies (69.0% DMD vs. 32.5% BMD).[ncbi.nlm.nih.gov]
Dystonia
  • He had comorbidity with dystonia, slight mental retardation, low stature and neuropathy. The brother of the proband's mother came to medical attention when he was 43 years old. He complained about muscle pain.[ncbi.nlm.nih.gov]

Workup

After a thorough history has been taken and a physical examination has been performed, a diagnosis of Becker muscular dystrophy may be confirmed with the following-

Laboratory Studies

Raised serum creatine kinase up to 10-100 times the normal level. Deletion analysis of the dystrophin gene shows specific deletions in majority of the cases. Muscle biopsy confirms the diagnosis of Becker muscular dystrophy. The biopsy shows dystrophic features and reduced dystrophin staining. Liver function tests might show elevated levels if aspartate transaminase and alanine transaminase.

Muscle histological studies will demonstrate the degeneration of muscle fibres and focal necrosis coupled with regeneration and fat replacement of the degenerated muscles. Laboratory studies are confirmatory if there is a family history of Becker muscular dystrophy and the typical symptoms. Genetic testing of carriers helps in diagnosing the disease in the prenatal antenatal period [5] [6]. An affected male will pass the defective genes to all his daughters which are carriers of the disease. The male children of these carriers have a 50% risk of being affected.

Imaging Studies

The development of scoliosis can be checked by spinal radiographs.

Other tests

An electromyography will guide in identifying the muscle groups to be checked by biopsy and it will aid in distinguishing a muscular and a primarily nerve process. An electromyogram might show normal nerve conduction with borderline/low evoked muscle potentials [7]. An electrocardiogram may show cardiomyopathy while an echocardiogram will show arrhythmias. Progressive respiratory weakness will be detected on pulmonary testing.

Atelectasis
  • Complications include upper airway obstruction, hypoventilation, atelectasis, congestive heart failure, cardiac dysrhythmias, respiratory failure, and difficulty weaning from mechanical ventilation.[clinicaladvisor.com]
  • […] surgical procedures are frequently recommended. 33 , 34 The patient with DMD or BMD faces unique risks not only in the operating room but also in the postoperative period. 35 , 36 Potential complications include respiratory failure, pulmonary aspiration, atelectasis[pediatrics.aappublications.org]
  • Daily use of incentive spirometer reduces atelectasis and pneumonia. X-rays are used to monitor spinal curvature because scoliosis adversely affects respiratory capacity.[emedicine.medscape.com]
Creatine Phosphokinase Increased
  • phosphokinase Increased serum CK Increased serum creatine kinase Increased serum creatine phosphokinase Last updated: 9/3/2016 Becker muscular dystrophy is inherited in an X-linked recessive manner.[rarediseases.info.nih.gov]
Abnormal ECG
  • One of them has an abnormal ECG that showed right ventricular hypertrophy and sinus tachycardia and the others have abnormal echocardiograms (ejection fraction ranging from 25-48% of normal levels) [ 31 ].[doi.org]
  • Decreased myocardial nNOS, increased iNOS and abnormal ECGs in mouse models of Duchenne muscular dystrophy. J Mol Cell Cardiol. 1999 ; 31 :1857–1862. Crossref Medline Google Scholar 23.[doi.org]

Treatment

Since it’s a genetic disorder, treatment is aimed only at giving symptomatic relief, preventing and treating complications. Close involvement of a pulmonologist, cardiologist and orthopaedist are important in case management. The pulmonologist will deal with pulmonary disorders arising due to the muscle weakness and breathing restriction [8].

Orthopedicians will be able to provide relief in the scoliosis that might occur at later age [9]. Surgical intervention might help correct scoliosis, contractures or muscle transfers to preserve mobility.

The discovery of various assistive devices helps them gain confidence and lead an independent life. Active lifestyle, own work, driving, enjoyment etc. can be experienced by people affected with Becker muscular dystrophy. They can even participate in various sports activities, theme parks, marathons under special categories.

Physiotherapy, recreational therapy, speech therapy, occupational therapy etc. aid in managing the symptoms of the disease. Regular cardiac and pulmonary monitoring is necessary.

Stretching of tight muscles and education regarding energy conservation techniques, joint protection techniques and preventing overuse fatigue are essential and can be achieved via physical therapy. Occupational therapy will assist in specific adaptations like zipper clothes, grab bars, elevated toilet seats in bathroom to make everyday chores simpler.

Dysphagia may improve with the help of a speech therapist. Avoiding specific solid foods and feeding positions can also help. The risk of aspiration might be evaluated with the use of high-end videofluoroscopy.

There is a promising future for some upcoming therapies that might help in treating patients with Becker muscular dystrophy. Gene therapy has been showing some promising results in the past decade and might evolve into an accurate therapy to correct targeted genetic defects [10] [11].

Prognosis

The progression of Becker muscular dystrophy is highly variable. Severity of the disease will depend on the onset of the disease and the age of the patient.

Becker muscular dystrophy results in slow but escalating disability and in due course of time the patients need a cane or a wheelchair. The degree of the symptoms and the complications will impact the quality of life of the patient.

Death can occur anytime after the age of 40 depending on the severity of the disease though some patients do have a nearly normal lifespan.

Etiology

Muscle cells remain intact due to dystrophin. Lack of dystrophin causes cells to be breakable and get easily damaged. The dystrophin gene is located on the X-chromosome.

Due to mutation of this dystrophin gene, there is insufficient dystrophin production in the muscles. This causes weakness of the muscles.

In case of Becker muscular dystrophy, there is presence of partially functioning dystrophin which prevents complete and rapid degeneration of the muscles.

Epidemiology

Becker muscular dystrophy is an X linked disorder hence it mainly affects males with an estimated incidence of one per 30,000 males [2]. There can be incidence of female carriers though most affected females are asymptomatic.

The age range for the onset of Becker muscular dystrophy is 2 to 21 years while the mean age for its onset is around 11 years [3]. The mean age at which the patient suffering from Becker muscular dystrophy becomes immobile is from about 12 to 30 years.

Death may be caused due to respiratory or cardiac failure at a mean age of 25 to 60 years.

Sex distribution
Age distribution

Pathophysiology

Becker muscular dystrophy is a neuromuscular disease characterized by gradually increasing muscle wasting and weakness due to degeneration of skeletal, smooth and cardiac muscle. The dystrophin gene is located on the X chromosome.

Since females have two X-chromosomes they remain only carriers and may not manifest any symptoms. Males have one X and one Y chromosome. Hence, if they inherit the defective gene they develop symptoms of muscle weakness and fatigue.

Dystrophin levels in Becker muscular dystrophy are generally 30-80% of normal [4]. Becker muscular dystrophy is less severe as it involves production of functional dystrophin which is absent in Duchenne muscular dystrophy.

Prevention

There are no guidelines for prevention of Becker muscular dystrophy.

Summary

Becker muscular dystrophy is an X-linked recessive inherited disorder. Becker muscular dystrophy was initially described by Becker and Kiener [1].

It is one of the many muscle diseases in which there is inadequate dystrophin production in the muscle cells causing the muscle cell membrane structure to be instable. Becker muscular dystrophy is related to Duchenne muscular dystrophy (DMD) as both are caused due to a mutated dystrophin gene. Becker muscular dystrophy is less severe than DMD.

Patient Information

Becker muscular dystrophy is an X-linked recessive inherited disorder. It is a disease affecting the muscles characterized by gradually increasing muscle wasting and weakness due to degeneration of skeletal, smooth and cardiac muscles. Becker muscular dystrophy and Duchenne muscular dystrophy are both caused due to a mutated dystrophin gene.

Becker muscular dystrophy is less severe than Duchenne as the gene is partially functioning. The dystrophin gene of X-chromosome undergoes mutation causing reduction in production of dystrophin in the muscles leading to weakness of the muscles.

This disorder manifests symptoms only in the males while females can be carriers of the disorder. Patients suffering from Becker muscular dystrophy experience delayed walking, running and jumping. They have great difficulty in climbing stairs due to weakness of the muscles. The gait is often affected leading to toe-walking gait. Due to this, they have a tendency to fall often. After falling they find it difficult to raise themselves without assistance.

Serum creatinin kinase levels may be elevated. An electromyography shows that weakness is caused by destruction of muscle tissue and not by nerve damage. A muscle biopsy or genetic testing confirms the diagnosis of Becker muscular dystrophy.

As age progresses Becker muscular dystrophy leads to severe muscular degeneration and hence, the patients need a cane or a wheelchair. The severity of the disorder and its complications will affect the quality of life of the patient. Activity is encouraged. Inactivity or sitting down for too long can worsen the muscle disease. Assistive devices can improve the mobility of the patient.

Physiotherapy, recreational therapy, speech therapy, occupational therapy etc. aid in managing the symptoms of the disease. Life-expectancy can be normal or shortened due to complications like dilated cardiomyopathy or respiratory failure.

References

Article

  1. Becker PE, Kiener F. A new x-chromosomal muscular dystrophy. Arch Psychiatr Nervenkr Z Gesamte Neurol Psychiatr. 1955;193(4):427-48.
  2. Cardiovascular health supervision for individuals affected by Duchenne or Becker muscular dystrophy. Pediatrics. Dec 2005;116(6):1569-73.
  3. Emery AE, Skinner R. Clinical studies in benign (Becker type) X-linked muscular dystrophy. Clin Genet. Oct 1976;10(4):189-201.
  4. Angelini C, Fanin M, Pegoraro E, et al. Clinical-molecular correlation in 104 mild X-linked muscular dystrophy patients: characterization of sub-clinical phenotypes. Neuromuscul Disord. Jul 1994;4(4):349-58.
  5. Menezes MP, North KN. Inherited neuromuscular disorders: Pathway to diagnosis. J Paediatr Child Health. Nov 3 2011
  6. Lim BC, Lee S, Shin JY, Kim JI, Hwang H, Kim KJ, et al. Genetic diagnosis of Duchenne and Becker muscular dystrophy using next-generation sequencing technology: comprehensive mutational search in a single platform. J Med Genet. Nov 2011;48(11):731-6.
  7. Rutkove SB, Darras BT. Electrical impedance myography for the assessment of children with muscular dystrophy: a preliminary study. J Phys Conf Ser. 2013;434(1)
  8. Jenkins HM, Stocki A, Kriellaars D, Pasterkamp H. Breath stacking in children with neuromuscular disorders. Pediatr Pulmonol. Aug 16 2013
  9. Pouwels S, de Boer A, Leufkens HG, Weber WE, Cooper C, van Onzenoort HA, et al. Risk of fracture in patients with muscular dystrophies. Osteoporos Int. Aug 15 2013
  10. Duan D. Myodys, a full-length dystrophin plasmid vector for Duchenne and Becker muscular dystrophy gene therapy. Curr Opin Mol Ther. Feb 2008;10(1):86-94.
  11. Bowles DE, McPhee SW, Li C, Gray SJ, Samulski JJ, Camp AS, et al. Phase 1 Gene Therapy for Duchenne Muscular Dystrophy Using a Translational Optimized AAV Vector. Mol Ther. Nov 8 2011

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Last updated: 2019-07-11 20:34