Becker muscular dystrophy (BMD) was eventually diagnosed in a boy with epilepsy and dysgnosia (delayed cognitive development), but relatively age-normal running and walkingabilities, researchers report in what they called a rare case study.
Later genetic testing revealed a duplicate mutation within the dystrophin gene, responsible for making a protein important for muscle integrity and movement.
Doctors examined the boy at age 9, two years after his first epileptic seizure, which started with convulsions and caused loss of consciousness, limb rigidity, turning of eyes and left head tilt. They noted his growth and development factors were behind those of his peers, but his walking and running motor skills were normal.
Examination also revealed slurred speech, poor math skills, enlarged gastrocnemius (calf) muscles, and weakness in the extremities. Laboratory tests showed an elevated serum creatine kinase level (indicative of muscle damage), normal cranial magnetic resonance imaging (MRI) and a low intelligence quotient (IQ) of 65.
A skeletal muscle tissue biopsy, testing the skeletal sarcolemma (sheath), came back slightly positive for dystrophin-N, indicating a partial deficiency of this protein.
The researchers suggested this deficiency may impair dystrophin glycoprotein complex function, associated with the contraction and relaxation of muscles.
Genetic testing also revealed a duplication mutation in several exons (segments coding for proteins or peptides) in the dystrophin gene (exons 37-44), a mutation never previously seen, the researchers said. It was determined that the mutation was inherited from the mother. They speculated that this mutation affects the structure and function of the protein Dp140, which has been shown to induce dysgnosia and epilepsy in other studies.
All of the patient’s clinical and genetic testing results met the criteria of a BMD diagnosis. The estimated incidence of BMD is rare, between 1.5 to 6 per 100,000 male births, and only 7.54% of those present with epilepsy. Concomitant dysgnosia is even more rare.
Because clinical manifestations of epilepsy, dysgnosia, and muscular dystrophy can be similar, the researchers suggested that a differential diagnoses should also include Fukuyama congenital muscular dystrophy (FCMD), a rare inherited dystrophy that is most common in Japan and marked by slow mental development, and limb-girdle muscular dystrophy.
The authors concluded that “definitive diagnosis depends on muscle biopsy and genetic analysis.”