summary Achondroplasia is a common congenital skeletal dysplasia caused by an autosomal dominant mutation in the fibroblast growth factor receptor 3 gene. Patients present with rhizomelic dwarfism with characteristic features such as lumbar and foramen magnum stenosis, frontal bossing and normal intelligence. Diagnosis is made based on family history associated with typical clinical and radiographic features. Treatment involves observation and physical therapy for majority of spinal anomalies. Surgical spinal instrumentation and fusion are indicated in patients with progressive spinal stenosis associated with neurological deficits. Epidemiology Incidence most common skeletal dysplasia Etiology Genetics autosomal dominant (AD) a sporadic mutation initially in >80%, then AD risk increases with advanced paternal age caused by G380 mutation of FGFR3 (fibroblast growth factor receptor 3, on chromosome 4P) gain of function mutation that increases inhibition of chondrocyte proliferation in the proliferative zone of the physis results in defect in endochondral bone formation a quantitative cartilage defect Associated conditions medical conditions weight control problems hearing loss tonsillar hypertrophy frequent otitis media spinal manifestations lumbar stenosis patients at risk due to short pedicles, thick facets and ligamentum flavum most likely to cause disability thoracolumbar kyphosis foramen magnum stenosis may cause periods of apnea or suddent death in infants Presentation Symptoms history normal intelligence delayed motor milestones symptoms of spinal stenosis pseudoclaudication and standing discomfort numbness and paresthesias subjective weakness Physical exam rhizomelic dwarfism humerus shorter than forearm and femur shorter than tibia normal trunk adult height ~ 50 inches facial features frontal bossing extremities trident hands (fingers same length with divergent ring and middle fingers) genu varum radial head subluxation muscular hypotonia in infancy spine thoracolumbar kyphosis excessive lordosis Imaging Radiographs lumbar spine findings shortened pedicles decreased interpedicular distance from L1-S1 (pathognomonic) vertebral wedging in thoracolumbar kyphosis posterior vertebral scalloping pelvis and extremities recommended views AP pelvis and weight-bearing hip-to-ankle AP findings champagne glass pelvis (pelvis is wider than deep) Squared iliac wings Inverted V in distal femur physis MRI indications to evaluate spinal stenosis adjunct to sleep study for screening foramen magnum stenosis in infants Treatment - Spine Conditions Thoracolumbar kyphosis nonoperative observation 90% improve bracing if persitent vertebral wedging after age 3 years may be poorly tolerated operative anterior strut corpectomy with posterior fusion or isolated posterior fusion indications bracing has failed kyphosis of > 45-60° Lumbar stenosis nonoperative weight loss, physical therapy, corticosteroid injections indications first line of treatment and frequently effective operative multilevel laminectomy and fusion indications spinal stenosis with severe symptoms nonoperative management has failed Lumbar hyperlordosis nonoperative observation treatment typically not required Foramen magnum stenosis operative surgical decompression of foramen magnum indications sleep apnea or cord compression Treatment - Extremity Conditions Genu varum operative tibial +/- femur osteotomies (based on CORA) indications pain or fibular thrust progressive deformity Short stature operative lower limb lengthening indications (very controversial) feasible due to soft tissue redundancy upper extremity lengthening indications upper extremity lengthening required to maintain ADL's Complications
QUESTIONS 1 of 18 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 Previous Next (OBQ18.249) A 3-year-old girl with short stature and rhizomelic shortening of the limbs presents to your office for follow-up of thoracolumbar kyphosis and trident hands. Her mother reports that her younger sister has a similar stature. Which of the following genetic pedigrees would be most consistent with this patient's condition? QID: 213145 FIGURES: A B C D E Type & Select Correct Answer 1 Figure A 5% (76/1382) 2 Figure B 46% (632/1382) 3 Figure C 9% (122/1382) 4 Figure D 13% (175/1382) 5 Figure E 26% (360/1382) L 4 Question Complexity A Question Importance Select Answer to see Preferred Response SUBMIT RESPONSE 2 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 (OBQ14.21) A 13-month-old child is found to have the abnormal spine imaging shown in Figure A. The deformity resolves spontaneously when he begins to walk. What is the most common form of inheritance for the gene defect associated with his underlying condition? QID: 5431 FIGURES: A Type & Select Correct Answer 1 Autosomal dominant 55% (1383/2494) 2 Autosomal recessive 25% (632/2494) 3 X-linked dominant 5% (135/2494) 4 X-linked recessive 10% (258/2494) 5 Mitochondrial 2% (60/2494) L 4 Question Complexity B 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 (SBQ13PE.99.1) Which of the following is associated with achondroplasia? QID: 214243 Type & Select Correct Answer 1 Atlanto-axial instability 35% (527/1524) 2 Central sleep apnea 36% (554/1524) 3 Dural ectasia 13% (201/1524) 4 Genu valgum 12% (177/1524) 5 Cauliflower ear 4% (60/1524) L 4 Question Complexity C Question Importance Select Answer to see Preferred Response SUBMIT RESPONSE 2 Review Tested Concept Review Full Topic (SBQ13PE.62) A 13-year-old girl presents with her mother for evaluation of left knee pain. Her mother also has short stature and is followed in the orthopaedic spine clinic. Both patients have frontal bossing. What is the genetic defect responsible for this condition? QID: 5155 FIGURES: A B Type & Select Correct Answer 1 Cartilage oligomeric matrix protein (COMP) on chromosome 17 6% (154/2484) 2 Cartilage oligomeric matrix protein (COMP) on chromosome 19 6% (151/2484) 3 Fibroblast growth factor receptor 3 (FGFR-3) 85% (2102/2484) 4 Runt-related transcription factor 2 (RUNX2) 2% (39/2484) 5 Core-binding factor subunit alpha-1 (CBF-alpha-1) 1% (14/2484) L 2 Question Complexity A 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 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 (OBQ12.82) Which of the following radiographs represents the condition associated with the genetic mutation G380R in the transmembrane domain of fibroblast growth factor receptor 3 (FGFR3)? QID: 4442 FIGURES: A B C D E Type & Select Correct Answer 1 Figure A 5% (254/5347) 2 Figure B 7% (349/5347) 3 Figure C 76% (4051/5347) 4 Figure D 9% (495/5347) 5 Figure E 2% (133/5347) L 2 Question Complexity A 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 (OBQ10.161) Dwarfism caused by a defect of fibroblast growth factor receptor-3 (FGFR3) is associated with all of the following traits EXCEPT: QID: 3254 Type & Select Correct Answer 1 Rhizomelic limb shortening 7% (253/3441) 2 Normal intelligence 4% (123/3441) 3 Frontal bossing 4% (127/3441) 4 Cervical spine instability 75% (2581/3441) 5 Spinal stenosis 10% (353/3441) L 2 Question Complexity C Question Importance Select Answer to see Preferred Response SUBMIT RESPONSE 4 Review Tested Concept Review Full Topic (OBQ09.10) Which of the following conditions is associated with a mutation in fibroblast growth factor receptor-3 (FGFR3)? QID: 2823 Type & Select Correct Answer 1 Marfan syndrome 3% (43/1602) 2 Gaucher's disease 0% (5/1602) 3 Fibrous dysplasia 4% (71/1602) 4 Achondroplasia 91% (1458/1602) 5 Diastrophic dysplasia 1% (23/1602) L 1 Question Complexity A Question Importance Select Answer to see Preferred Response SUBMIT RESPONSE 4 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. (SAE07PE.11) Where is the underlying defect in a rhizomelic dwarf with the findings shown in Figure 5? QID: 6071 FIGURES: A Type & Select Correct Answer 1 Type I collagen 4% (16/405) 2 Type II collagen 3% (14/405) 3 Collagen oligomeric protein (COMP) 9% (38/405) 4 Sulfate transport 7% (30/405) 5 Fibroblast growth factor receptor 3 75% (304/405) L 3 Question Complexity E Question Importance Select Answer to see Preferred Response SUBMIT RESPONSE 5 Review Tested Concept Review Full Topic (OBQ06.139) A 7-year-old presents to your office for general orthopedic evaluation at the request of his primary care physician. A clinical picture of the patient with his taller sibling is shown in Figure A. What physeal zone is affected by the mutation leading to this patient's condition? QID: 325 FIGURES: A Type & Select Correct Answer 1 Zone of hypertrophy 24% (801/3365) 2 Reserve zone 2% (57/3365) 3 Zone of proliferation 73% (2440/3365) 4 Primary spongiosa 1% (37/3365) 5 Secondary spongiosa 0% (10/3365) L 2 Question Complexity A Question Importance Select Answer to see Preferred Response SUBMIT RESPONSE 3 Review Tested Concept Review Full Topic (OBQ06.226) Achondroplasia results from abnormal chondrocyte function in the physis. What receptor is defective and what region of the physis is affected? QID: 237 Type & Select Correct Answer 1 FGFR-3, zone of proliferation 76% (1102/1443) 2 FGFR-2, zone of proliferation 5% (76/1443) 3 FGFR-3, zone of hypertrophy 15% (223/1443) 4 FGFR-2, zone of hypertrophy 2% (36/1443) 5 COMP, zone of hypertrophy 0% (2/1443) L 2 Question Complexity B Question Importance Select Answer to see Preferred Response SUBMIT RESPONSE 1 Review Tested Concept Review Full Topic
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