PSEUDOHYPERTROPHIC muscular dystrophy of Duchenne is the most common form of muscular dystrophy seen in children. It is transmitted as a sex-linked recessive gene, occurs primarily in males, is generally manifest by the 3rd year of life, and results in death, usually before the 25th year. There is a characteristic progression of muscular weakness starting in the pelvic girdle and trunk, and eventually involving virtually all the striated musculature, including the tongue, facial, masticatory, and respiratory muscles.1,2 The visceral musculature is spared. Enlargement of the calf muscles and occasionally of other muscle groups accounts for the name pseudohypertrophic muscular dystrophy. The diagnosis in the advanced stages is not difficult. However, in the early stages it may have to depend on laboratory studies, such as serum enzymology, electromyography, and muscle biopsy, because clinical signs of weakness may not appear until approximately 50% of the maximum muscle strength is lost.
SANDERS LJ, PERLSTEIN MA. Speech Mechanism in Pseudohypertrophic Muscular Dystrophy. Am J Dis Child. 1965;109(6):538-543. doi:10.1001/archpedi.1965.02090020540008