Genetic, clinical, and pathologic features of Duchenne and Becker muscular dystrophies

Type	Gene location	Protein	Inheritance	Clinical features	Pathology/ CPK
Dystrophinopathies
Duchenne	Xp21	Dystrophin	XR	Onset: 2-5 years Pseudohypertrophy Diminished IQ Cardiac involvement Rapid decline Death by age 20-30 years	Severe dystrophic changes Absent dystrophin by immunohistochemistry Dystrophin <5 percent of normal amount by Western blot Striking CK elevation early on
Intermediate "outliers"	Xp21	Dystrophin	XR	Intermediate	Dystrophin 5-20 percent normal amount by Western blot of muscle protein
Becker	Xp21	Dystrophin	XR	Onset: variable More benign course	Less marked changes Reduced dystrophin by immunohistochemistry Normal or abnormal size dystrophin, amount >20 percent by Western blot

CK, creatine kinase; XR, X-linked recessive.

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