Snapshot A 10-year-old boy is brought to the pediatric endocrinologist due to short stature. The mother reports that her son is not as tall as his classmates, and this is causing him stress. On physical exam, there is macrocephaly with frontal bossing, shortening of the arms and legs, and lumbar lordosis. Arrangements are made for genetic molecular testing. Introduction Clinical definition a congenital skeletal dysplasia that results in shortened extremities and macrocephaly also known as dwarfism Etiology autosomal dominant gain-of-function mutation in fibroblast growth factor receptor (FGFR3) Pathogenesis constitutively active FGFR3 activity impairs chondrocyte proliferation and differentiation this in turn leads to impaired long bone formation (via endochondrial ossification) enlarged head relative to limbs (via membranous ossification) Associated findings most common cause of dwarfism normal life span, intelligence, and reproduction Presentation Symptoms asymptomatic Physical exam macrocephaly frontal bossing shortening of arms and legs proximal/rhizomelic segments are more notable lumbar lordosis kyphoscholiosis Treatment Conservative monitoring, preventing, and addressing complications e.g., leg bowing is managed with physical therapy Differential Diagnosis Cleidocranial dysplasia key distinguishing factors due to mutation in RUNX2 (autosomal dominant or de novo) cranial abnormalities (delayed suture or fontanelle closure, brachycephaly, mandibular prognathism, and hypertelorism) dental anomalies (supernumerary teeth, malocclusion, delayed loss of primary teeth, and delayed eruption of permanent teeth) missing or underdeveloped clavicles
QUESTIONS 1 of 6 1 2 3 4 5 6 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 (M1.MK.17.4722) A 3-year-old male is brought in to his pediatrician by his mother because she is concerned that he is not growing appropriately. Physical examination is notable for frontal bossing and shortened upper and lower extremities. His axial skeleton appears normal. He is at the 7th percentile for height and 95th percentile for head circumference. He demonstrates normal intelligence and is able to speak in three-word sentences. He first sat up without support at twelve months and started walking at 24 months. Genetic analysis reveals an activating mutation in a growth factor receptor. Which of the following physiologic processes is most likely disrupted in this patient’s condition? QID: 108535 Type & Select Correct Answer 1 Intramembranous ossification 11% (38/351) 2 Osteoblast maturation 9% (32/351) 3 Endochondral ossification 64% (223/351) 4 Production of type I collagen 10% (35/351) 5 Bone resorption 3% (12/351) M 1 Question Complexity C Question Importance Select Answer to see Preferred Response SUBMIT RESPONSE 3 Review Tested Concept Review Full Topic (M1.MK.15.72) A young boy presents to your office for evaluation. He is not growing as quickly as his twin brother (Figure A). Genetic testing reveals a mutation in the fibroblast growth factor receptor gene.What is the most likely mode of inheritance? QID: 106538 FIGURES: A Type & Select Correct Answer 1 Autosomal dominant 77% (165/214) 2 Autosomal recessive 13% (28/214) 3 X-linked recessive 4% (9/214) 4 X-linked dominant 2% (4/214) 5 Mitochondrial 2% (5/214) M 1 Question Complexity E Question Importance Select Answer to see Preferred Response SUBMIT RESPONSE 1 Review Tested Concept Review Full Topic (M1.MK.15.27) A 9-month-old female infant is brought in by her mother to the pediatrician because she is concerned that her daughter is not growing normally. On physical exam, the head circumference is 95th percentile and the height is 5th percentile. The child has disproportionate growth such that both the upper and lower extremities show a rhizomelic pattern of shortening, but the axial skeleton appears to be normal. The child appears to have normal intelligence, but has delayed motor milestones; specifically, she is not able to roll or sit up by herself. Which of the following best describes the mode of inheritance for this disorder? QID: 107010 Type & Select Correct Answer 1 Autosomal recessive 16% (34/211) 2 Autosomal dominant 64% (135/211) 3 X-linked recessive 6% (13/211) 4 X-linked dominant 4% (8/211) 5 Mitochondrial pattern of inheritance 7% (14/211) M 1 Question Complexity E 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
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