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Metabolic reasoning
Whole-map thinking. Each case is a chain of cause → effect that ends in the labs: why DKA has ketones and hyperglycemia, why a drinker goes hypoglycemic, why an infant with MCAD deficiency spills no ketones. Walk through the chain on the map, then order it yourself, answer the why questions, or diagnose from the labs.
A teenager breathing fast and deep
Maya, 14, is brought in by her mother with 2 days of nausea, vomiting and diffuse abdominal pain, and 1 week of thirst, urination and weight loss. She is confused, breathing fast and deep (RR 32), HR 118, BP 98/60, afebrile. Her breath smells sweet and fruity.
| Glucose | 489 mg/dL | ↑ |
| HCO₃⁻ | 12 mEq/L | ↓ |
| Anion gap | 24 | ↑ |
| pH | 7.22 | ↓ |
| pCO₂ | 20 mmHg | ↓ |
| β-Hydroxybutyrate | 8.3 mmol/L | ↑↑ |
| Urine ketones | 4+ | ↑ |
| K⁺ | 5.8 mEq/L | ↑ |
| Na⁺ | 128 mEq/L | ↓ |
| Triglycerides | 519 mg/dL | ↑ |
Diabetic ketoacidosis (new type 1 diabetes)
One hormonal derangement — absolute insulin deficiency with unopposed glucagon — explains every value.
Condition card: Diabetic ketoacidosis (DKA) →Pathway map →
- Autoimmune destruction of β-cells → absolute insulin deficiency; glucagon is unopposed.
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Pathways involved: Lipolysis, carnitine shuttle & β-oxidation, Ketogenesis & ketone body use, Gluconeogenesis, Glycolysis. Drill them one at a time in Metabolic pathways.