Becker’s muscular dystrophy is less severe version of the Duchenne muscular dystrophy. Duchenne muscular dystrophy is a quntitative disorder of dystrophin, which means absence of dytrophin while Becker’s muscular dsytrophy is qualitative disorder of dystrophin, which means dystrophin is present but it has abnormal structure and function.
It is an X-linked recessive genetic disorder with abnormality located at Xp21 gene locus, which is responsible for translation of production of protein dystrophin. Due to this genetic abnormality, dystrophin is present in lower than normal amounts and is mostly of an abnormal molecular weight.
Dystrophin-glycoprotein complex is a protein complex found in the sarcolemma (covering membrane of the muscle fiber) that connects the contractile apparatus of the muscle fiber with the extracellular matrix. Since Becker’s muscular dystrophy is a disorder predominantly of quality (abnormal molecular weight) and to a lesser extent of quantity (levels lower than the normal) of dystrophin hence it leads to reduced capacity of skeletal muscle to bear routine wear tear. This reduced endurance of the muscle eventually leads to disruption of its cellular structure resulting in its death and destruction.
3. Clinical Features:
I. Onset and Progression:
Its onset is late during later part of the first decade of life and its progression is also slow. Slow progression of this disease keeps the patient mobile at least till 3rd decade of life when the patient becomes wheel chair dependent.
II. Cardiac Involvement:
Cardiac abnormalities are even more severe as compared to those encountered in Duchenne muscular dystrophy. Cardiomyopathy leads to development of heart failure and can eventually become the cause of death.
III. Other Features:
Patients suffering from Becker’s muscular dystrophy also develop pseudohypertrophy of skeletal muscles, scoliosis and respiratory problems.
IV. Female Carriers:
Female carriers of abnormal genes may develop cardiomyopathy with raised CK levels.