Contributed by Natashia Seemann1, Robert Hammond1,2,3, Dr. Chitra Prasad4, Craig Campbell1,2,5
1Schulich School of Medicine & Dentistry, University of Western Ontario, Canada, 2Department(s) of Clinical Neurological Sciences,
3 Pathology, 4Genetics and Metabolics and 5 Pediatrics, London Health Sciences Centre, Ontario, Canada
A 9-year old girl presented with a 6 month history of progressive shoulder and back discomfort associated with generalized weakness and exercise intolerance.
Her past medical history was complicated by spina bifida in association with a Chiari type II malformation and hydrocephalus. She had undergone a myelomeningocele repair, tethered cord release and placement of a VP shunt. Developmental motor milestones were delayed (walking began at age 2) but she eventually walked unassisted. She had mild bowel and bladder dysfunction.
On physical exam, muscle bulk and tone were normal in the upper limbs but shoulder adduction was weak, graded 4/5. Shoulder abduction and elbow flexion were graded 4+/5. Muscle bulk in the lower limbs was decreased. Tone was normal. Hip flexion and knee flexion were graded as 4+/5. When asked to lie supine then rise to a standing position she demonstrated a partial Gower's maneuver.
Nerve conduction studies were normal, but electromyography demonstrated myopathic units in the shoulder girdle muscles and quadriceps. A muscle biopsy was performed.
Perimysial and endomysial connective tissues were found to be generous and fibre size variation was markedly increased on the basis of scattered hypertrophic and atrophic fibres. Individual and small clusters of degenerating and regenerating fibres were present and associated with light adjacent mononuclear infiltrates. Internal nuclei were increased and scattered rounded, hypereosinophilic (hypercontracted) fibres were present.
Dystrophin immunohistochemistry (N-terminus, rod domain and C-terminus) identified a highly variable expression pattern from fibre to fibre with approximately half of the fibres showing normal expression and the remainder having markedly reduced, patchy or no expression. Dystrophin expression levels were highly variable from fascicle to fascicle. Figure 1 shows the skeletal muscle biopsy reveals endomysial and perimysial fibrosis and increased fiber size variation. Internal nuclei are increased in frequency and there centrally in the field of view are degenerating and regenerating fibers, while Figure 2 shows scattered hyperstaining, rounded (hypercontracted) fibers. Figure 3 shows spectrin immunostains and in figure 4 immunostains for dystrophin were used.