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{{WBRQuestion
{{WBRQuestion
|QuestionAuthor={{Rim}}
|QuestionAuthor= {{YD}} (Reviewed by  {{YD}})
|ExamType=USMLE Step 1
|ExamType=USMLE Step 1
|Prompt=A 17 year old male achondroplastic dwarf is brought by his mother to the physician's office to inquire about his condition. The physician informs the patient that his condition is caused by an abnormal functioning of a growth factor receptor that affects his bone development. Which of the following abnormalities of osteogenesis most likely have occurred in this patient?
|MainCategory=Pathophysiology
|Explanation=Achondroplasia is a form of chondrodysplasia and is the most common cause of dwarfism. It is an autosomal dominant disorder that causesfailure of endochondral ossification with normal intramembranous ossification due to constitutive activation of fibroblast growth factor (FGF3) receptor. As such, patients tend to have normal heads (intramembranous ossification of the skull) with short limbs (failure of endochondral ossification of long bones of the extremities). I
|SubCategory=Musculoskeletal/Rheumatology
 
|MainCategory=Pathophysiology
FGF3 receptor is activated by intrinsic tyrosine kinase activity, similar to all other growth factor receptors and insulin receptors.
|SubCategory=Musculoskeletal/Rheumatology
 
|MainCategory=Pathophysiology
Educational Objective:
|SubCategory=Musculoskeletal/Rheumatology
FGF3 receptor has an intrinsic tyrosine kinase signaling pathway. Constitutive activation of FGF3 receptor causes achondroplasia, an autosomal dominant disorder.
|MainCategory=Pathophysiology
 
|MainCategory=Pathophysiology
Reference:
|MainCategory=Pathophysiology
Laederich MB, Horton WA. Achondroplasia: pathogenesis and implications for future treatment. Curr Opin in Pediatr. 2010;22(4):516-523.
|SubCategory=Musculoskeletal/Rheumatology
|MainCategory=Pathophysiology
|SubCategory=Musculoskeletal/Rheumatology
|MainCategory=Pathophysiology
|SubCategory=Musculoskeletal/Rheumatology
|MainCategory=Pathophysiology
|SubCategory=Musculoskeletal/Rheumatology
|MainCategory=Pathophysiology
|MainCategory=Pathophysiology
|SubCategory=Musculoskeletal/Rheumatology
|Prompt=A 17-year-old male achondroplastic dwarf is brought by his mother to the physician's office to inquire about his condition. The physician informs the patient that his condition is caused by an abnormal functioning of a growth factor receptor that affects his bone development. Which of the following abnormalities of osteogenesis have most likely occurred in this patient?
|Explanation=[[Achondroplasia]] is a form of [[chondrodysplasia]] and is the most common cause of [[dwarfism]]. It is an autosomal dominant disorder characterized by constitutive activation of fibroblast growth factor (FGF3) receptor, which is a receptor tyrosine kinase (RTK) that employs the intrinsic tyrosine kinase pathway. Achondroplasia manifests with failure of endochondral ossification and normal intramembranous ossification. Patients typically have normal heads (normal intramembranous ossification of the skull) with short limbs (failure of endochondral ossification of long bones of the extremities).


|AnswerA=Failure of intramembranous ossification with normal endochondral ossification
|AnswerA=Failure of intramembranous ossification with normal endochondral ossification
|AnswerAExp=Achondroplasia is characterized by failure of endochondral ossification with normal intramembranous ossification.
|AnswerAExp=[[Achondroplasia]] is characterized by failure of [[endochondral ossification]] with normal [[intramembranous ossification]].
|AnswerB=Continuous activation of chondrocytes
|AnswerB=Continuous activation of chondrocytes
|AnswerBExp=FGF3 activation leads to inhibition of chondrocyte activation
|AnswerBExp=FGF3 activation results in inhibition of [[chondrocyte]] activation.
|AnswerC=Failure of both endochondral and intramembranous ossifications.
|AnswerC=Failure of both endochondral and intramembranous ossification processes
|AnswerCExp=Achondroplasia is characterized by failure of endochondral ossification with normal intramembranous ossification.
|AnswerCExp=[[Achondroplasia]] manifests with failure of [[endochondral ossification]] and normal [[intramembranous ossification]].
|AnswerD=Constitutive inhibition of FGF3 receptors
|AnswerD=Constitutive inhibition of FGF3 receptors
|AnswerDExp=FGF3 receptors are constitutively activated in achondroplasia
|AnswerDExp=[[FGF3 receptor]]s are constitutively activated in achondroplasia.
|AnswerE=Tyrosine kinase overactivity negatively influences proliferation of chondrocytes
|AnswerE=Tyrosine kinase overactivity
|AnswerEExp=FGF3 is a growth factor that has an intrinsic tyrosine kinase signaling pathway. Constitutive activation of the pathway inhibits the proliferation of chondrocytes and leads to failure of endochondral ossification in achondroplasia.
|AnswerEExp=Similar to other [[growth factor]]s and [[insulin]], FGF3 is a growth factor that employs the intrinsic [[tyrosine kinase]] signaling pathway. Constitutive activation of the pathway inhibits the proliferation of [[chondrocyte]]s and leads to failure of [[endochondral ossification]] among patients with [[achondroplasia]].
|EducationalObjectives=FGF3 receptor is a receptor tyrosine kinase (RTK) that employs the intrinsic tyrosine kinase signaling pathway. Constitutive activation of FGF3 receptor causes achondroplasia.
|References=Laederich MB, Horton WA. Achondroplasia: pathogenesis and implications for future treatment. Curr Opin in Pediatr. 2010;22(4):516-523.<br>
First Aid 2014 page 419
|RightAnswer=E
|RightAnswer=E
|WBRKeyword=tyrosine, kinase, signaling, pathway, achondroplasia, failure, longitudinal, bone, growth, ossification, osteogenesis, limb, skull, limbs, FGF3, fibroblast, growth, factor, dwarf, dwarfism, endochondral, intramembranous, membranous, chondrocyte, inhibition, constitutive, acitvation, receptor, receptors, autosomal, dominant
|WBRKeyword=Tyrosin kinase signaling pathway, Receptor tyrosine kinase, RTK, Growth factors, FGF3 receptor, Achondroplasia, Autosomal dominant disorder, Dwarfism, Endochondral ossification, Intramembranous ossification
|Approved=No
|Approved=Yes
}}
}}

Latest revision as of 01:37, 28 October 2020
Author [[PageAuthor::Yazan Daaboul, M.D. (Reviewed by Yazan Daaboul, M.D.)]]
Exam Type ExamType::USMLE Step 1
Main Category MainCategory::Pathophysiology
Sub Category SubCategory::Musculoskeletal/Rheumatology
Prompt [[Prompt::A 17-year-old male achondroplastic dwarf is brought by his mother to the physician's office to inquire about his condition. The physician informs the patient that his condition is caused by an abnormal functioning of a growth factor receptor that affects his bone development. Which of the following abnormalities of osteogenesis have most likely occurred in this patient?]]
Answer A AnswerA::Failure of intramembranous ossification with normal endochondral ossification
Answer A Explanation [[AnswerAExp::Achondroplasia is characterized by failure of endochondral ossification with normal intramembranous ossification.]]
Answer B AnswerB::Continuous activation of chondrocytes
Answer B Explanation [[AnswerBExp::FGF3 activation results in inhibition of chondrocyte activation.]]
Answer C AnswerC::Failure of both endochondral and intramembranous ossification processes
Answer C Explanation [[AnswerCExp::Achondroplasia manifests with failure of endochondral ossification and normal intramembranous ossification.]]
Answer D AnswerD::Constitutive inhibition of FGF3 receptors
Answer D Explanation [[AnswerDExp::FGF3 receptors are constitutively activated in achondroplasia.]]
Answer E AnswerE::Tyrosine kinase overactivity
Answer E Explanation [[AnswerEExp::Similar to other growth factors and insulin, FGF3 is a growth factor that employs the intrinsic tyrosine kinase signaling pathway. Constitutive activation of the pathway inhibits the proliferation of chondrocytes and leads to failure of endochondral ossification among patients with achondroplasia.]]
Right Answer RightAnswer::E
Explanation [[Explanation::Achondroplasia is a form of chondrodysplasia and is the most common cause of dwarfism. It is an autosomal dominant disorder characterized by constitutive activation of fibroblast growth factor (FGF3) receptor, which is a receptor tyrosine kinase (RTK) that employs the intrinsic tyrosine kinase pathway. Achondroplasia manifests with failure of endochondral ossification and normal intramembranous ossification. Patients typically have normal heads (normal intramembranous ossification of the skull) with short limbs (failure of endochondral ossification of long bones of the extremities).

Educational Objective: FGF3 receptor is a receptor tyrosine kinase (RTK) that employs the intrinsic tyrosine kinase signaling pathway. Constitutive activation of FGF3 receptor causes achondroplasia.
References: Laederich MB, Horton WA. Achondroplasia: pathogenesis and implications for future treatment. Curr Opin in Pediatr. 2010;22(4):516-523.
First Aid 2014 page 419]]

Approved Approved::Yes
Keyword WBRKeyword::Tyrosin kinase signaling pathway, WBRKeyword::Receptor tyrosine kinase, WBRKeyword::RTK, WBRKeyword::Growth factors, WBRKeyword::FGF3 receptor, WBRKeyword::Achondroplasia, WBRKeyword::Autosomal dominant disorder, WBRKeyword::Dwarfism, WBRKeyword::Endochondral ossification, WBRKeyword::Intramembranous ossification
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