summary Duchenne Muscular Dystrophy is a common congenital condition caused by an X-linked recessive mutation leading to the absence of dystrophin protein that affects young males who present with progressive muscle weakness, scoliosis, and cardiomyopathy. Diagnosis is made with DNA testing showing an absence of the dystrophin protein. Treatment involves a multidisciplinary approach to address cardiomyopathy, pulmonary dysfunction, scoliosis, and foot deformities. Epidemiology Prevalence 2-3/10,000 Demographics affects young males only age of onset is between 2-6 years of age Etiology Pathophysiology dystrophin absence leads to poor muscle fiber regeneration progressive replacement of muscle tissue with fibrous and fatty tissue skeletal and cardiac muscle lose elasticity and strength Genetics X-linked recessive Xp21.2 dystrophin gene defect due to point deletion and nonsense mutation one third of cases result from spontaneous mutations Associated conditions orthopaedic manifestations calf pseudohypertrophy scoliosis equinovarus foot deformity joint contractures nonorthopaedic conditions cardiomyopathy static encephalopathy Becker's Muscular Dystrophy similar to Duchenne's in that it is sex-linked recessive calf pseudohypertrophy is present CPK is elevated differs from Duchenne's in that dystrophin protein is decreased instead of absent later onset with slower progression and longer life expectancy (average diagnosis occurs at age 8 compared to 2 years of age with Duchenne's) more prone to cardiomyopathy Physical Exam Symptoms progressive weakness affecting proximal muscles first (begins with gluteal muscle weakness) gait abnormalities delayed walking toe walking clumsy, waddling gait difficulty climbing stairs, hopping, or jumping decreased motor skills Physical exam calf pseudohypertrophy (infiltration of normal muscle with connective tissue) deep tendon reflexes present (unlike spinal muscular atrophy) lumbar lordosis compensates for gluteal weakness Gower's sign rises by walking hands up legs to compensate for gluteus maximus and quadriceps weakness Trendelenburg sign Evaluation Labs markedly elevated CPK levels (10-200x normal) CPK leaks across defective cell membrane Muscle biopsy will show connective tissue infiltration and foci of necrosis will show absent dystrophin with staining DNA testing shows absent dystrophin protein EMG myopathic decreased amplitude, short duration, polyphasic motor Differential Similarity and Distinguishing features of differential diagnosis Similar traits to Duchenne's Distinguishing traits from Duchenne's Becker's • Calf pseudohypertrophy• Markedly elevated CPK• X-linked transmission • Becker's has slower progression of weakness with diagnosis made later (~8 yrs)• Prone to cardiomyopathy Spinal muscular atrophy • Proximal weakness • Onset of weakness is earlier in childhood• Absent deep tendon reflexes and fasciculations• CPK levels are normal• Pseudohypertrophy is absent Emery-Dreifuss dystrophy • Similar clinical picture • No calf pseudohypertrophy• CPK levels near normal• Elbow and ankle contractures develop early Limb girdle dystrophy • Progressive motor weakness • No calf pseudohypertrophy• CPK levels are only mildly elevated Guillain-Barre syndrome • Acute onset of weakness • Absent deep tendon reflexes• CPK levels are normal Treatment Nonoperative corticosteroid therapy (prednisone 0.75 mg/kg/day) indications 5 to 7-year-old child with progressive disease goals to maintain ambulatory capacity as long as possible outcomes significant positive effect on disease progression acutely improves strength, slows progressive weakening, prevents scoliosis formation, and prolongs ambulation delays deterioration of pulmonary function side effects osteonecrosis weight gain cushingoid appearance GI symptoms mood lability headaches short stature cataracts pulmonary care with nightly ventilation rehabilitation techniques physical therapy for range of motion exercises adaptive equipment power wheelchairs KAFO bracing (controversial) Operative soft tissue releases to prolong ambulation indications ambulatory child with Duchenne's techniques hip abduction contractures treated by release of iliotibial band Hip flexion contractures treated by release of sartorius, rectus femoris, and tensor fascia lata hamstring releases Achilles tendon and posterior tibialis lengthenings postoperative care early mobilization and ambulation to prevent deconditioning scoliosis surgery (see below) Scoliosis Introduction considered a neurogenic curve occurs in 95% of patients after becoming wheelchair dependent curve progresses rapidly from age 13 to 14 years begins with mild hyperlordosis progresses with general kyphosis and scoliosis with varying degrees of pelvic obliquity progresses 1° to 2° per month starting at age 8 to 10 years patients may become bedridden by age 16 treatment is complicated by restrictive pulmonary disease (significant decrease in forced vital capacity) cardiac and pulmonary function studies should be obtained pre-operatively as significant declines in function of both organ systems may make spinal fusion too high-risk Treatment nonoperative bracing is contraindicated may interfere with respiration operative early PSF with instrumentation indications curve 20-30° in nonambulatory patient treat early before pulmonary function declines can wait longer ~ 40° if responding well to corticosteroids FVC drops ≤ 35% rapidly progressive curve PSF with instrumentation to pelvis indications curves ≥ 40° pelvic obliquity ≥ 10° lumbar curve where apex is lower than L1 complications malignant hyperthermia is common intraoperatively pretreat with dantrolene intraoperative cardiac events anterior and posterior spinal fusion indications rarely for stiff curves Equinovarus Foot Introduction common foot deformity seen with Duchenne muscular dystrophy Pathoanatomy muscle imbalance secondary to muscle replacement with fibrofatty tissue Diagnosis made upon clinical exam Treatment nonoperative stretching, physical therapy, and night time AFO use operative Tendinoachilles lengthening with posterior tibialis tendon transfer, toe flexor tenotomies Prognosis Most are unable to ambulate independently by age 10 Most are wheelchair dependent by age 15 Most die of cardiorespiratory problems by age 20
QUESTIONS 1 of 20 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 Previous Next Sorry, this question is for PEAK Premium Subscribers only Upgrade to PEAK Sorry, this question is for PEAK Premium Subscribers only Upgrade to PEAK Sorry, this question is for PEAK Premium Subscribers only Upgrade to PEAK (SBQ13PE.21) A 16-year-old male presents to your clinic complaining of imbalance while sitting in his wheelchair. On exam, he has has a right thoracic and left lumbar parapinal prominence, pelvic obliquity, and equinovarus foot deformities. He has been wheelchair bound since age 12, and used ambulatory assistive devices from ages 5-11. His maternal uncle had the same progressive condition. The patient and family desire an improved sitting posture. An AP scoliosis x-ray is shown in Figure A. You recommend a T2-Pelvis posterior spinal fusion. Which of the following medical workups is appropriate for this patient prior to surgery? QID: 4991 FIGURES: A Type & Select Correct Answer 1 Rheumatology panel and a muscle biopsy 5% (183/3589) 2 MRI to rule out dural ectasia or syrinx 27% (953/3589) 3 Echocardiogram and pulmonary function studies 65% (2335/3589) 4 Genetic screening of all siblings and first cousins 2% (70/3589) 5 Trial of Baclofen pump and physical therapy prior to fusion 1% (29/3589) L 3 Question Complexity C Question Importance Select Answer to see Preferred Response SUBMIT RESPONSE 3 Review Tested Concept Review Full Topic (SBQ13PE.67) A 4-year-old boy presents to your clinic for evaluation of 'clumsiness.' His parents state that he began walking at 30 months of age. They note that he is not able to keep up with his peers in athletic activities. He is unable to climb steps without the aid of a handrail. On exam, he stands with increased lumbar lordosis and a wide based stance. When asked to rise from a seated position on the floor, the child first rolls into a crawling position on all four limbs, stands up by extending his knees and uses his upper extremities bracing against his thighs to help elevate his trunk. You confirm the diagnosis with serum enzyme assay followed by DNA analysis. The parents ask you what the chances are of their child passing on this genetic disease to his male offspring. QID: 5175 Type & Select Correct Answer 1 0% 62% (1246/2014) 2 25% 7% (150/2014) 3 50% 20% (410/2014) 4 75% 1% (15/2014) 5 100% 9% (181/2014) L 4 Question Complexity B Question Importance Select Answer to see Preferred Response SUBMIT RESPONSE 1 Review Tested Concept Review Full Topic (SBQ13PE.36) Which of the following is true regarding scoliosis in patients with untreated Duchenne muscular dystrophy (DMD)? QID: 5051 Type & Select Correct Answer 1 Small curves are likely to remain stable over time 2% (52/2571) 2 50% of all patients with DMD will develop scoliosis 18% (461/2571) 3 Spinal fusion should be offered when the Cobb angle reaches 20 to 30 degrees 69% (1769/2571) 4 Scoliosis in DMD is responsive to bracing 3% (70/2571) 5 Scoliosis surgery is ideally performed at skeletal maturity patients with DMD 8% (208/2571) L 3 Question Complexity B Question Importance Select Answer to see Preferred Response SUBMIT RESPONSE 3 Review Tested Concept Review Full Topic This is an AAOS Self Assessment Exam (SAE) question. Orthobullets was not involved in the editorial process and does not have the ability to alter the question. If you prefer to hide SAE questions, simply turn them off in your Learning Goals. (SAE13BS.10) A 5-year-old boy has a history of delayed walking and difficulty climbing stairs. Physical examination shows a positive Gower sign and scoliosis. Laboratory tests show elevated serum creatine phosphokinase. A mutation of what protein results in this disorder? QID: 8242 Type & Select Correct Answer 1 Dystrophin 96% (415/432) 2 Collagen type I 1% (4/432) 3 Neurofibromin 1% (6/432) 4 Runt-related transcription factor 2 (Runx2) 1% (4/432) L 1 Question Complexity D Question Importance Select Answer to see Preferred Response SUBMIT RESPONSE 1 Review Tested Concept Review Full Topic (OBQ13.199) Which of the following is most commonly inherited as a X-linked recessive disorder? QID: 4834 Type & Select Correct Answer 1 Charcot-Marie-Tooth disease 6% (216/3848) 2 Marfan's syndrome 2% (82/3848) 3 Larsen's syndrome 2% (88/3848) 4 Duchenne's muscular dystrophy 83% (3209/3848) 5 Turner's syndrome 6% (233/3848) L 2 Question Complexity B Question Importance Select Answer to see Preferred Response SUBMIT RESPONSE 4 Review Tested Concept Review Full Topic Sorry, this question is for PEAK Premium Subscribers only Upgrade to PEAK Sorry, this question is for PEAK Premium Subscribers only Upgrade to PEAK Sorry, this question is for PEAK Premium Subscribers only Upgrade to PEAK Sorry, this question is for PEAK Premium Subscribers only Upgrade to PEAK Sorry, this question is for PEAK Premium Subscribers only Upgrade to PEAK (OBQ10.49) A 9-year-old boy with Duchenne muscular dystrophy has increasing difficulty with ambulation. He denies back pain, difficulty sitting in a chair, or shortness of breath. Annual screening spine radiographs demonstrate a 20 degree thoracolumbar curve. Which of the following statements best describes the appropriate treatment plan for his scoliosis? QID: 3137 Type & Select Correct Answer 1 Given the poor prognosis, surgical treatment is not appropriate 2% (70/3099) 2 Posterior spinal fusion should be performed before curve progresses beyond 30 degrees 68% (2121/3099) 3 Posterior spinal fusion should be performed if the curve progresses to greater than 55 degrees 12% (380/3099) 4 Posterior spinal fusion should be performed if FVC drops below 60% 9% (294/3099) 5 With appropriate bracing, curve progression and surgical treatment will most likely be unnecessary 7% (217/3099) L 2 Question Complexity C Question Importance Select Answer to see Preferred Response SUBMIT RESPONSE 2 Review Tested Concept Review Full Topic (OBQ09.131) What is the inheritance pattern for Duchenne's muscular dystrophy? QID: 2944 Type & Select Correct Answer 1 autosomal recessive 4% (57/1486) 2 autosomal dominant 6% (88/1486) 3 X-linked recessive 78% (1162/1486) 4 X-linked dominant 12% (172/1486) 5 random 0% (5/1486) L 2 Question Complexity B Question Importance Select Answer to see Preferred Response SUBMIT RESPONSE 3 Review Tested Concept Review Full Topic Sorry, this question is for PEAK Premium Subscribers only Upgrade to PEAK This is an AAOS Self Assessment Exam (SAE) question. Orthobullets was not involved in the editorial process and does not have the ability to alter the question. If you prefer to hide SAE questions, simply turn them off in your Learning Goals. (SAE07PE.43) Duchenne’s muscular dystrophy is a genetic disorder that is transmitted by which of the following modes of inheritance? QID: 6103 Type & Select Correct Answer 1 X-linked 92% (274/298) 2 Autosomal-dominant 4% (11/298) 3 Autosomal-recessive 2% (7/298) 4 Chromosomal duplication 0% (1/298) 5 Chromosomal deletion 1% (4/298) L 1 Question Complexity E Question Importance Select Answer to see Preferred Response SUBMIT RESPONSE 1 Review Tested Concept Review Full Topic Sorry, this question is for PEAK Premium Subscribers only Upgrade to PEAK Sorry, this question is for PEAK Premium Subscribers only Upgrade to PEAK (SBQ04PE.47) An 11-year-old boy is evaluated after reporting progressive difficulty walking. After extensive workup, he is diagnosed with Becker muscular dystrophy. Which of the following best describes the characteristic findings associated with this diagnosis? QID: 2232 Type & Select Correct Answer 1 Pseudohypertrophy of the calves, markedly increased creatine kinase levels, and abnormal dystrophin 77% (1886/2458) 2 Proximal muscle weakness occuring early in childhood, absent deep tendon reflexes and fasciculations 8% (192/2458) 3 Mildly elevated creatine kinase levels, severe limb contractures present at an early age 3% (85/2458) 4 Acute onset of weakness, hypotonia, and arefelxia resulting from postinfectious demyelination of the peripheral nerves 2% (41/2458) 5 X-linked transmission, absence of dystrophin, and significantly increased creatine kinase levels 10% (234/2458) L 2 Question Complexity D Question Importance Select Answer to see Preferred Response SUBMIT RESPONSE 1 Review Tested Concept Review Full Topic
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Pediatric Gait Abnormality - Unknown Diagnosis (C1523) Pediatrics - Duchenne Muscular Dystrophy E 6/4/2013 273 1 21