WBR0279
| Author | [[PageAuthor::Ogheneochuko Ajari, MB.BS, MS [1]]] |
|---|---|
| Exam Type | ExamType::USMLE Step 1 |
| Main Category | MainCategory::Biochemistry |
| Sub Category | SubCategory::General Principles |
| Prompt | [[Prompt::A 55-year old known diabetic and hypertensive patient presents to the physician’s office with a history of progressive loss of vision. Physical examination shows a blood pressure of 160/90mmHg, pulse of 90/minute with peripheral neuropathy. Laboratory findings include a blood glucose level of 160g/dl. An eye examination confirms the presence of bilateral cataracts. Which of the following intracellular accumulations is a likely cause of the patient’s symptoms?]] |
| Answer A | AnswerA::Fructose |
| Answer A Explanation | AnswerAExp::Incorrect. Fructose accumulation causes essential fructosuria which would result due to the deficiency of fructokinase. It is a benign condition that is most often asymptomatic |
| Answer B | AnswerB::Sorbitol |
| Answer B Explanation | AnswerBExp::Correct- See explanation |
| Answer C | AnswerC::Galactose |
| Answer C Explanation | AnswerCExp::Incorrect. Galactose accumulation would result as a result of galactokinase deficiency and galactose appears in blood and urine and may cause infantile cataracts. It is a relatively mild condition |
| Answer D | AnswerD::Galactitol |
| Answer D Explanation | [[AnswerDExp::Incorrect. Galactitol accumulation is due to the deficiency or the absence of the enzyme galactose-1-phosphate uridyltransferase, which causes galactosemia, an autosomal recessive disorder with symptoms such as failure to thrive, jaundice, hepatomegaly, infantile cataracts and mental retardation.]] |
| Answer E | AnswerE::Glycogen |
| Answer E Explanation | AnswerEExp::Incorrect. Intracellular accumulations of glycogen would lead to abnormal glycogen metabolism and could lead to a group of disorders called glycogen storage diseases |
| Right Answer | RightAnswer::B |
| Explanation | [[Explanation::In glucose metabolism, an alternative method of trapping glucose in the cell is its conversion to sorbitol by the enzyme aldose reductase. Some tissues then convert sorbitol to fructose using the enzyme sorbitol dehydrogenase. In diabetics with chronic hyperglycemia, their tissues lack this enzyme and therefore, they are at risk for intracellular sorbitol accumulation, which results in osmotic damage causing cataracts, retinopathy and peripheral neuropathy.
Educational Objective Tissues lacking sorbitol dehydrogenase are at risk for intracellular sorbitol accumulation seen in diabetics with chronic hyperglycemia. Reference: First AID for the USMLE Step 1 2011 Pgs 104, 110 |
| Approved | Approved::Yes |
| Keyword | |
| Linked Question | Linked:: |
| Order in Linked Questions | LinkedOrder:: |