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{{WBRQuestion | {{WBRQuestion | ||
|QuestionAuthor={{ | |QuestionAuthor={{YD}} (Reviewed by {{YD}}) | ||
|ExamType=USMLE Step 1 | |ExamType=USMLE Step 1 | ||
|MainCategory=Biochemistry | |MainCategory=Biochemistry | ||
| Line 21: | Line 21: | ||
|MainCategory=Biochemistry | |MainCategory=Biochemistry | ||
|SubCategory=General Principles | |SubCategory=General Principles | ||
|Prompt=A 22 year old | |Prompt=A 22-year-old man is brought by his roommate to the emergency department for acute motor weakness and sensation loss in his left arm. The patient reports that he was studying with his roommate when he suddenly felt heaviness and numbness in his left arm. Brain CT scan reveals no bleeding. Brain MRI is remarkable for changes consistent with an acute ischemic stroke. Further laboratory evaluation is significant for elevated concentrations of [[homocysteine]] in the blood and urine. The patient is then diagnosed with a hereditary disease, and is transferred to ophthalmologic check-up. Which of the following is characteristic of the lens subluxation that is associated with this patient's condition? | ||
|Explanation=Homocystinuria is characterized by an accumulation of [[homocysteine]] in the serum and an increased excretion of homocysteine in the urine. It is associated with thromboembolic events at an early age, | |Explanation=Classic [[homocystinuria]] is an autosomal recessive hereditary disorder characterized by impaired [[methionine]] metabolism. The amino acid methione is normally converted to homocysteine during its degradation. In homocystinuria, this process is impaired. Homocystinuria is characterized by an accumulation of [[homocysteine]] in the serum and an increased excretion of homocysteine in the urine. It is associated with thromboembolic events at an early age, early [[myopia]], [[ectopia lentis]], and [[marfanoid feature]]s. [[Ectopia lentis]] is commonly characterized by lens subluxation that is usually downwards and inwards. | ||
|AnswerA=Downwards and outwards | |AnswerA=Downwards and outwards | ||
|AnswerAExp=Homocystinuria is associated with lens subluxation downwards and inwards. | |AnswerAExp=Homocystinuria is associated with lens subluxation that is downwards and inwards. | ||
|AnswerB=Downwards and inwards | |AnswerB=Downwards and inwards | ||
|AnswerBExp=Homocystinuria is associated with lens subluxation downwards and inwards. | |AnswerBExp=Homocystinuria is associated with lens subluxation that is downwards and inwards. | ||
|AnswerC=Upwards and outwards | |AnswerC=Upwards and outwards | ||
|AnswerCExp=Homocystinuria is associated with lens subluxation downwards and inwards. | |AnswerCExp=Homocystinuria is associated with lens subluxation that is downwards and inwards. | ||
|AnswerD=Upwards and inwards | |AnswerD=Upwards and inwards | ||
|AnswerDExp=Homocystinuria is associated with lens subluxation downwards and inwards. | |AnswerDExp=Homocystinuria is associated with lens subluxation that is downwards and inwards. | ||
|AnswerE=No specific | |AnswerE=No specific association | ||
|AnswerEExp=Homocystinuria is associated with lens subluxation downwards and inwards. | |AnswerEExp=Homocystinuria is associated with lens subluxation that is downwards and inwards. | ||
|EducationalObjectives= | |EducationalObjectives=[[Homocystinuria]] is associated with development of ophthalmic complications, such as early [[myopia]] and [[ectopia lentis]]. [[Ectopia lentis]] is commonly characterized by lens subluxation that is usually downwards and inwards. | ||
|References=Makris | |References=Makris M. Hyperhomocysteinemia and thrombosis. Clin Lab Haematol. 2000;22(3):133-143.<br> | ||
First Aid 2015 page 108 | First Aid 2015 page 108 | ||
|RightAnswer=B | |RightAnswer=B | ||
|WBRKeyword= | |WBRKeyword=Stroke, Homocystinuria, Ectopia lentis, Autosomal recessive, Lens dislocation, Opthalmic complications, Eye, Genetics, Metabolism, Thrombosis, Homocysteine | ||
|Approved= | |Approved=Yes | ||
}} | }} | ||
Revision as of 23:22, 15 August 2015
| Author | [[PageAuthor::Yazan Daaboul, M.D. (Reviewed by Yazan Daaboul, M.D.)]] |
|---|---|
| Exam Type | ExamType::USMLE Step 1 |
| Main Category | MainCategory::Biochemistry |
| Sub Category | SubCategory::General Principles |
| Prompt | [[Prompt::A 22-year-old man is brought by his roommate to the emergency department for acute motor weakness and sensation loss in his left arm. The patient reports that he was studying with his roommate when he suddenly felt heaviness and numbness in his left arm. Brain CT scan reveals no bleeding. Brain MRI is remarkable for changes consistent with an acute ischemic stroke. Further laboratory evaluation is significant for elevated concentrations of homocysteine in the blood and urine. The patient is then diagnosed with a hereditary disease, and is transferred to ophthalmologic check-up. Which of the following is characteristic of the lens subluxation that is associated with this patient's condition?]] |
| Answer A | AnswerA::Downwards and outwards |
| Answer A Explanation | AnswerAExp::Homocystinuria is associated with lens subluxation that is downwards and inwards. |
| Answer B | AnswerB::Downwards and inwards |
| Answer B Explanation | AnswerBExp::Homocystinuria is associated with lens subluxation that is downwards and inwards. |
| Answer C | AnswerC::Upwards and outwards |
| Answer C Explanation | AnswerCExp::Homocystinuria is associated with lens subluxation that is downwards and inwards. |
| Answer D | AnswerD::Upwards and inwards |
| Answer D Explanation | AnswerDExp::Homocystinuria is associated with lens subluxation that is downwards and inwards. |
| Answer E | AnswerE::No specific association |
| Answer E Explanation | AnswerEExp::Homocystinuria is associated with lens subluxation that is downwards and inwards. |
| Right Answer | RightAnswer::B |
| Explanation | [[Explanation::Classic homocystinuria is an autosomal recessive hereditary disorder characterized by impaired methionine metabolism. The amino acid methione is normally converted to homocysteine during its degradation. In homocystinuria, this process is impaired. Homocystinuria is characterized by an accumulation of homocysteine in the serum and an increased excretion of homocysteine in the urine. It is associated with thromboembolic events at an early age, early myopia, ectopia lentis, and marfanoid features. Ectopia lentis is commonly characterized by lens subluxation that is usually downwards and inwards. Educational Objective: Homocystinuria is associated with development of ophthalmic complications, such as early myopia and ectopia lentis. Ectopia lentis is commonly characterized by lens subluxation that is usually downwards and inwards. |
| Approved | Approved::Yes |
| Keyword | WBRKeyword::Stroke, WBRKeyword::Homocystinuria, WBRKeyword::Ectopia lentis, WBRKeyword::Autosomal recessive, WBRKeyword::Lens dislocation, WBRKeyword::Opthalmic complications, WBRKeyword::Eye, WBRKeyword::Genetics, WBRKeyword::Metabolism, WBRKeyword::Thrombosis, WBRKeyword::Homocysteine |
| Linked Question | Linked:: |
| Order in Linked Questions | LinkedOrder:: |