WBR0320: Difference between revisions

Jump to navigation Jump to search
← Older editNewer edit →
VisualWikitext
Rim Halaby (talk | contribs)
CMEUser, Bureaucrats, nocaptcha, Administrators
27,346 edits
No edit summary
No edit summary
Line 1: Line 1:
{{WBRQuestion
{{WBRQuestion
|QuestionAuthor={{Rim}}
|QuestionAuthor={{Rim}}, {{AJL}} {{Alison}}
|ExamType=USMLE Step 1
|ExamType=USMLE Step 1
|MainCategory=Biochemistry
|MainCategory=Biochemistry
Line 20: Line 20:
|MainCategory=Biochemistry
|MainCategory=Biochemistry
|SubCategory=Neurology
|SubCategory=Neurology
|Prompt=A one year old boy is brought by his parents to the physician's office for failure to thrive. Upon further questioning, the mother explains that the child is aggressive, has abnormal movements, and is always chewing off his fingertips and lips. Physical examination is remarkable for swelling of the joints, spasticity, and hyperreflexia. Based on the illustration below, which enzyme is most likely deficient in this patient?
|Prompt= Brought by his parents, a 1-year-old male presents to the physician's office for failure to thrive. Upon further questioning, the mother explains that the child is aggressive, moves abnormally, and frequently chews his fingertips and lips. Upon physical examination, you observe a swelling of the first metatarsophalangeal joint, spasticity, and hyperreflexia. Which of the following enzymes in the diagram is most likely deficient in this patient?


[[Image:WBR0320.png|500px]]
[[Image:WBR0320.png|500px]]
|Explanation=The patient has symptoms and signs consistent with Lesch-Nyhan syndrome, an X-linked disorder characterized by the absence of hypoxanthine-ribosyl-phosphoribosyltransferase (HGPRT), which normally converts hypoxanthine to inosinic acid (IMP) and guanine to guanylic acid (GMP). As a result, the purine salve pathway is lost and the patient has to undergo de novo purine synthesis. Excessive uric acid production in urea and increase in purine synthesis enzymes, along with the absence of any HGPRT activity and hyperuricemia, are present. Patients typically present with mental retardation, failure to thrive, choreoathetosis, and self-aggressive behavior with self-mutilation. Joint swelling is due to gout due to hyperuricemia.


Educational Objective: Absence of HGPRT causes Lesch-Nyhan syndrome, characterized by mental retardation, self-mutilation, hyperuricemia, and choreoathetosis.
|Explanation=The patient demonstrates symptoms and signs indicative of [[Lesch-Nyhan syndrome]], an X-linked disorder characterized by the absence of [[HGPRT|hypoxanthine-ribosyl-phosphoribosyltransferase (HGPRT)]], which converts hypoxanthine to inosine monophosphate (IMP), guanine to guanosine monophasphate (GMP), and xanthine to xanthosine monophosphate. As a result, the purine salvage pathway is hindered and the patient has to undergo de novo purine synthesis. [[Lesch-Nyhan syndrome]] manifests with excessive uric acid production in urea and an increase in purine synthesis, leading to to hyperuricemia. Patients typically present with mental retardation, failure to thrive, choreoathetosis, and self-mutilation. Joint swelling results from gout, due to hyperuricemia.
 
|EducationalObjectives= Absence of HGPRT leads to [[Lesch-Nyhan syndrome]], characterized by mental retardation, self-mutilation, hyperuricemia, and choreoathetosis.
|AnswerA=A
|AnswerA=A
|AnswerAExp="A" does not correspond to hypoxanthine-guanosine-phosphoribosyltransferase (HGPRT).
|AnswerAExp="A" does not correspond to HGPRT.
|AnswerB=B
|AnswerB=B
|AnswerBExp="B" corresponds to HGPRT.
|AnswerBExp="B" corresponds to HGPRT.
Line 38: Line 39:
|RightAnswer=B
|RightAnswer=B
|WBRKeyword=HGPRT, lesch, nyhan, syndrome, self-mutilation, self, mutilation, aggressive, behavior,aggression, hyperuricemia, gout, hypoxanthine, guanine, phosphoribosyltransferase, purine, salvage, de, novo, X-linked, congenital, disorder
|WBRKeyword=HGPRT, lesch, nyhan, syndrome, self-mutilation, self, mutilation, aggressive, behavior,aggression, hyperuricemia, gout, hypoxanthine, guanine, phosphoribosyltransferase, purine, salvage, de, novo, X-linked, congenital, disorder
|Approved=No
|Approved=Yes
}}
}}

Revision as of 18:16, 11 July 2014
Author [[PageAuthor::Rim Halaby, M.D. [1], Alison Leibowitz [2] (Reviewed by Alison Leibowitz)]]
Exam Type ExamType::USMLE Step 1
Main Category MainCategory::Biochemistry
Sub Category SubCategory::Neurology
Prompt [[Prompt::Brought by his parents, a 1-year-old male presents to the physician's office for failure to thrive. Upon further questioning, the mother explains that the child is aggressive, moves abnormally, and frequently chews his fingertips and lips. Upon physical examination, you observe a swelling of the first metatarsophalangeal joint, spasticity, and hyperreflexia. Which of the following enzymes in the diagram is most likely deficient in this patient?

]]

Answer A AnswerA::A
Answer A Explanation AnswerAExp::"A" does not correspond to HGPRT.
Answer B AnswerB::B
Answer B Explanation AnswerBExp::"B" corresponds to HGPRT.
Answer C AnswerC::C
Answer C Explanation AnswerCExp::"C" does not correspond to HGPRT.
Answer D AnswerD::D
Answer D Explanation AnswerDExp::"D" does not correspond to HGPRT. It corresponds to adenosine deaminase (ADA). Its absence causes severe combined immunodeficiency (SCID).
Answer E AnswerE::E
Answer E Explanation AnswerEExp::"E" does not correspond to HGPRT.
Right Answer RightAnswer::B
Explanation [[Explanation::The patient demonstrates symptoms and signs indicative of Lesch-Nyhan syndrome, an X-linked disorder characterized by the absence of hypoxanthine-ribosyl-phosphoribosyltransferase (HGPRT), which converts hypoxanthine to inosine monophosphate (IMP), guanine to guanosine monophasphate (GMP), and xanthine to xanthosine monophosphate. As a result, the purine salvage pathway is hindered and the patient has to undergo de novo purine synthesis. Lesch-Nyhan syndrome manifests with excessive uric acid production in urea and an increase in purine synthesis, leading to to hyperuricemia. Patients typically present with mental retardation, failure to thrive, choreoathetosis, and self-mutilation. Joint swelling results from gout, due to hyperuricemia.

Educational Objective: Absence of HGPRT leads to Lesch-Nyhan syndrome, characterized by mental retardation, self-mutilation, hyperuricemia, and choreoathetosis.
References: ]]

Approved Approved::Yes
Keyword WBRKeyword::HGPRT, WBRKeyword::lesch, WBRKeyword::nyhan, WBRKeyword::syndrome, WBRKeyword::self-mutilation, WBRKeyword::self, WBRKeyword::mutilation, WBRKeyword::aggressive, WBRKeyword::behavior, WBRKeyword::aggression, WBRKeyword::hyperuricemia, WBRKeyword::gout, WBRKeyword::hypoxanthine, WBRKeyword::guanine, WBRKeyword::phosphoribosyltransferase, WBRKeyword::purine, WBRKeyword::salvage, WBRKeyword::de, WBRKeyword::novo, WBRKeyword::X-linked, WBRKeyword::congenital, WBRKeyword::disorder
Linked Question Linked::
Order in Linked Questions LinkedOrder::
Retrieved from "https://www.wikidoc.org/index.php?title=WBR0320&oldid=991994"