| Fact | Explanation |
|---|---|
| Usually occurs in males. Rarely in females. [1] | This is an X linked recessive disorder. Thus presence of abnormal X chromosome causes the disease in male. But in females either both X chromosomes have to be affected or lyonization of the normal X chromosome has to occur, where the X chromosome with abnormal gene will be active leading to manifestation of symptoms. [1][2][14] |
| Muscle cramps/ Myalgia [3][4] | Maybe induced by activity. [3] |
| Abnormal/ waddling/ Trendelenburg gait. [4] | Due to proximal muscle weakness. Abnormal gait manifest around 10-15 years of age, which is a later presentation than what is seen in Duchenne muscular dystrophy. [4] |
| Thigh muscle wasting | Generalized progressive atrophy occurs, but thigh muscle wasting could be the only sign because quadriceps myopathy can occur in isolation. [3] |
| Contractures of ankles, knees, hips and then joints of the upper body [12] | This occur due to replacement of elastin with scar tissue and results in reduced mobility of the joint. [12] |
| Bulky calf 'muscles'. | This is now believed to be due to increased number of muscle fibers and its branches which may later undergo fibrosis. [13] Seen at the age of 15-20 years. [4] |
| Difficulty in climbing stairs and standing up. [4][9] | Begins in the 3rd decade of life. [4] May even occur later in life. [9] |
| Toe walking and lumber lordosis. [10] | This is due to weak hip extensors which causes anterior pelvic tilt moving the trunk forward, patient avoids this by lumber lordosis. Weak hip extensors also cause buckling of the knee, to avoid this patient maintains a flexion at knee and planter flexion of ankle. Planter flexion during mid and late stance helps to keep the gravity anterior to knee and keeps it from buckling. [10] |
| Fatigue, dyspnoea, palpitaion, syncope, ankle oedema, cough [4] | Dilated cardiomyopathy, hypertrophic cardiomyopathy, arrhythmias, heart failure, sudden cardiac death may occur in patients with Becker muscular dystrophy. [4] [1] Symptoms usually begin at 3rd decade of life [4] and is the most common cause of death in Becker muscular dystrophy. [3] |
| Cognitive impairment. [7] | Due to reduced dystrophin in brain leading to central nervous system dysfunction. [5] May occur even in absence of muscle weakness. [6] This can range from severe mental retardation to specific deficits.[7] |
| Epilepsy.[5] | 7.54% of patients with Becker muscular dystrophy have associated epilepsy. Thought to be due to lack of dystrophin in brain leading to neurological dysfunction. [5] |
| Painless dark colour urine [11] | Due to myoglobinuria, usually occurs episodicallly. [3][4] |
| Macroglossia/ red-green color blindness [8] | These have been found in association with Becker muscular dystrophy in some patients. [8] |
| Presence of family history | This is an X linked recessive disorder, thus, a family history compatigle with X linked disorder will be present. [3] |
| Fact | Explanation |
|---|---|
| Patient maybe unable to walk and maybe wheelchair bound. [1] | This occurs usually at the age of 16 years. [1] |
| Pseudo hypertrophy of the calves. | This is now believed to be due to increased number of muscle fibers and its branches [2] rather than due to fatty infiltration of the calves' as believed earlier. This may later undergo fibrosis. [2] |
| Flexion contractures of the ankles, knees, elbows. [1] | Occurs later in the course of disease. [1] |
| Reduced muscle power in proximal than in distal group of limb muscles. [1] | Weak quadriceps femoris could be the only positive sign too. This is usually symmetric and continuous monitoring of the power will show progressively worsening weakness. [1] |
| Power of neck flexors are preserved. [1] | Unlike in Duchenne muscular dystrophy in which the neck flexors are also affected. [1] |
| Positive Gower's sign. | Due to the proximal muscle weakness when the child is asked to stand up from supine or sitting position, child first roll onto prone position, with upper and lower limbs extended. Then the trunk's weight mainly borne by upper limb, the body is pushed backwards over the extended legs. Then the hands are placed on the knees to extend the hip and the child climbs on himself till he is in erect position. [5] This sign is not specific to Becker muscular dystrophy and is seen in all diseases associated with pelvic girdle muscle weakness. [5] |
| Cardiovascular examination. [3] | It is essential to perform cardiovascular examination since Becker muscular dystrophy is associated with cardiac involvement and it is the most common cause of morbidity and mortality of these patients. [1] Look for features of heart failure- difficulty breathing, ankle edema, elevated JVP, increased pulse rate, reduced blood pressure, displaced diffuse apex, crepitations in lungs on auscultation owing to pulmonary edema. [4] |
| Fact | Explanation |
|---|---|
| Duchenne muscular dystrophy. | Age of presentation is much earlier than in Becker, and may present with motor developmental delay. [1] While onset of symptoms in Duchenne muscular dystrophy is 10.5 +/- 7.2 years, in Becker muscular dystrophy it is 2.3 +/- 13, therefore there is an overlap of 18.42% at the age of 4 years.[4] This is due to active muscle degeneration occurring much earlier (about 10 years earlier) in Duchenne than in Becker muscular dystrophy. [2] |
| Limb-Girdle muscular dystrophy | DNA analysis would help to differentiate this from Becker in which dystrophin gene deletion can be demonstrated. [3] |
| Kugelberg-Welander disease | DNA analysis would help to differentiate this from Becker in which dystrophin gene deletion can be demonstrated. [3] |
| Facioscapulohumeral dystrophy | Usually have facial and shoulder girdle weakness but also can present with upper limb or lower limb weakness. Unlike in Becker muscular dystrophy weakness is asymmetrical and cardiac involvement is usually absent. [5][6] |
| Congenital myopathies. | Symptoms start very early in life, in around few months of life, unlike in Becker and about 35% become ventilatory dependent or succumb to illness by the age of 11 years,[7] unlike in Becker muscular dystrophy in which this would be the age when initial symptoms start to manifest. |
| Fact | Explanation |
|---|---|
| Immunostaining of biopsy muscle [3] | Staining of dystrophin isoform is patchy due to reduced dystrophin. This is due to deletions/ duplications or point mutations of dystrophin gene. [1] |
| Western blot for dystrophin in biopsy of skeletal muscle [5] | Both immunofluorescence detections and western blot give compatible results and are of high value in detection of Becker muscular dystrophy. [5] |
| PCR of dystrophin | Becker muscular dystrophy occur due to deletion/ duplication of dystrophin gene which occurs in about two thirds of patients, this is via PCR. [6][7] |
| Ultrasound scan of the calves. [2] | Abnormal echo intensities of the muscle may occur due to fat infiltration of the muscle causing pseudo hypertrophy of the calf. Both absolute and pseudo hypertrophy of the calves have been observed in Becker muscular dystrophy. [2] |
| Creatinine kinase.[3] | Elevated levels are seen in affected individuals, 5 times higher than the normal value. [3] Estimation of creatine kinase is superior to estimation of pyruvate kinase in detection of Becker muscular dystrophy. [4] |
| Fact | Explanation |
|---|---|
| Elevated CK-MB [1] | Shows cardiac damage.[1] Cardiac involvement is not associated with clinical severity of illness, there for careful monitoring is necessary even if muscle weakness is only mild. [2] |
| ECG | May reveal arrythmias/ cardiac damage [1] |
| 2D echocardiogram | Anatomy of the myocardium can be viewed, hypertrophied/ dilated cardiomyopathy can be seen and ejection fraction could be calculated. [1] |
| Thallium myocardial scintigraphy | Reduced myocardial perfusion. [1] |
| Cardiac magnetic resonance imaging (cMRI), | Hypertrophied/ dilated myocardium, fibrosis can be visualised. [1] |
| Magnetic resonance spectroscopy (MRS) | Shows reduced dystrophin. |
| Endomyocardial biopsy | Fibrosis, hypertrabeculation of left ventricle, atrophic myocardiocytes can be seen. [1] |
| Fact | Explanation |
|---|---|
| Creatine kinase of patient mother and brothers. [1][2] | About 30 % of the carriers will have 2 to 10 times higher levels of creatine kinase. [1] |
| DNA analysis of the mother of the affected child. [2] | Becker muscular dystrophy is and X linked recessive disorder, thus mainly seen in males. Since all the males inherit the X chromosome from their mother, any deletion/ of the gene may also be present in mother's chromosome (as seen in two third of the cases), one third of the cases are spontaneous mutations. [3] Dystrophin specific DNA probe and creatine kinase is used to calculate the risk of being a carrier of affected gene. This is helpful to genetic council the parents regarding having another child/ deciding whether other siblings maybe affected. [2] |
| Prenatal diagnosis-Chorionic villus sampling. [4] | Can be done in carriers who want to have children of their own. [4] |
| Fact | Explanation |
|---|---|
| Multidisciplinary approach towards symptomatic treatment. | Physicians, occupational therapists, counselors, orthopedic surgeons and pediatricians together have to make patient specific decisions to manage the patients. [4] |
| Genetic counselling. | Becker muscular dystrophy is an X linked recessive disorder, thus affects males more than females and two thirds of affected males inherit the deformed gene from the mother while one third develop spontaneous mutation. [1] Deformed gene of the mother can be diagnosed by DNA analysis following screening with creatine kinase levels, together the carrier state can be detected and if mother is a carrier 50% of sons will be affected. Father do not carry the gene defect to the son, but all the daughters will be carriers.[1] [2] |
| Pharmocological therapy for cardiomyopathy. | Has been proved to improve cardiac status of the patient. Patients with cardiac abnormality usually survive up to 30 years of age at which they need cardiac transplant or may succumb to illness. [3] |
| Invasive and noninvasive mechanical ventilation/ Implanted cardiac devices.[4] | If the intercostal muscles become weak there could be a respiratory compensation which could be supported by artificial ventilation. |
| Fact | Explanation |
|---|---|
| Currently there is no specific therapy for Becker muscular dystrophy but a mode of gene therapy is being widely investigated. [1] | Eteplirsen, drisapersen- still undergoing clinical trials. They are in phase II / III of clinical trials and seen to have increased expression of dystrophin. [2] |