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A 4-year-old boy has difficulty climbing stairs and uses his hands to "walk up" his legs when rising from the floor (Gowers sign). His CK is markedly elevated at 15,000 U/L.
XLR; DMD gene (dystrophin) - frameshift/nonsense variants (no functional protein)
- Onset 2-5 years
- Progressive proximal weakness (pelvic > shoulder)
- Gowers maneuver (rise from floor)
- Calf pseudohypertrophy
- Elevated CK (10,000-50,000+)
- Cardiomyopathy, respiratory failure
- Loss of ambulation by ~12 years
- Death typically by 20s-30s
- CK, DMD gene testing, muscle biopsy (absent dystrophin)
- Corticosteroids, cardiac management, exon-skipping therapies for eligible variants
"Duchenne's 4 D's": Dystrophin (absent), Dilated cardiomyopathy (a leading cause of death), Distal limb pseudohypertrophy (calf), DNA test for dystrophin gene mutation.
"CD" for diagnosis: 1st step: CK (elevated). 2nd step: DNA test for dystrophin gene mutation.