WBR0145
| Author | [[PageAuthor::Rim Halaby, M.D. [1]]] |
|---|---|
| Exam Type | ExamType::USMLE Step 1 |
| Main Category | MainCategory::Genetics |
| Sub Category | SubCategory::Renal |
| Prompt | [[Prompt::A 2-year-old girl is brought to the pediatrician by her mother for excessive drinking and urination. The patient’s mother recalls an uneventful pregnancy and delivery. The patient had a normal neonatal growth course and successfully met previous developmental milestones. The patient’s vital signs reveal a temperature of 37.2 C (99.0F), pulse of 140 bpm, and blood pressure of 70/50 mmHg. On physical examination, the patient’s skin turgor shows delayed recoil and her extremities are mottled and cyanotic. Physical examination is otherwise unremarkable. Laboratory testing is significant for metabolic alkalosis, hypokalemia, elevated plasma renin and aldosterone. Urinalysis reveals markedly elevated urinary calcium and potassium with no evidence of casts, hematuria, or leukocyturia. What is the most likely diagnosis?]] |
| Answer A | AnswerA::21 hydroxylase deficiency |
| Answer A Explanation | [[AnswerAExp::21 hydroxylase deficiency, a form of congenital adrenal hyperplasia, typically presents with hypotension, but also with hyperkalemia and signs of masculinization due to female hermaphrodism.]] |
| Answer B | AnswerB::Gitelman syndrome |
| Answer B Explanation | [[AnswerBExp::Gitelman syndrome is a differential diagnosis of Bartter syndrome. Unlike the latter, Gitelman syndrome reveals electrolyte values as as if someone is on thiazide diuretics with absence of elevated urinary calcium levels. Gitelman syndrome usually presents later than Bartter syndrome.]] |
| Answer C | AnswerC::Secreting pituitary tumor |
| Answer C Explanation | [[AnswerCExp::The patient does not have the typical presentation of any secreting pituitary tumor.]] |
| Answer D | AnswerD::Bartter syndrome |
| Answer D Explanation | [[AnswerDExp::Bartter syndrome is a rare inherited form of hypokalemic metabolic alkalosis. At least 5 mutations of ion transport across renal cells in the thick ascending loop of Henle have been implicated in Bartter syndrome, hence comprising several subtypes of the disease. Patients with Bartter syndrome typically manifest their symptoms as early as within early years of life. It is characterized by polyuria, polydypsia, and signs of dehydration on physical examination. Serum and urinary electrolytes would be similar to patients on loop diuretics, with elevated urinary calcium and potassium.]] |
| Answer E | AnswerE::Lipoid nephrosis |
| Answer E Explanation | [[AnswerEExp::Lipoid nephrosis, or minimal change disease, is a glomuerulonephritis characterized by normal appearing glomeruli under light microscopy. Electron microscopy, however, reveals foot process effacement with selective loss of albumin. Minimal change disease is a type of nephritic syndrome that would not have the presentation of the patient in the vignette.]] |
| Right Answer | RightAnswer::D |
| Explanation | [[Explanation::Bartter syndrome is a rare inherited form of hypokalemic metabolic alkalosis. It is characterized by polyuria, polydypsia, and signs of dehydration on physical examination. Serum and urinary electrolytes would be similar to patients on loop diuretics, with elevated urinary calcium and potassium.
Educational objective: Bartter syndrome causes hypokalemic metabolic alkalosis similar to patients on loop diuretics, but manifests at an early age. |
| Approved | Approved::No |
| Keyword | WBRKeyword::Renal, WBRKeyword::Bartter syndrome, WBRKeyword::Aldosterone, WBRKeyword::Renin, WBRKeyword::RAAS, WBRKeyword::Metabolic alkalosis, WBRKeyword::Electrolyte |
| Linked Question | Linked:: |
| Order in Linked Questions | LinkedOrder:: |