Differential Diagnosis
- Single most likely diagnosis
- D Surreptitious vomiting: The patient's presentation of significant weight loss, muscle weakness, and muscle cramps, along with laboratory findings of hypokalemia (low potassium), metabolic alkalosis (elevated bicarbonate and pH), and low urine chloride, is highly suggestive of surreptitious vomiting. Vomiting leads to the loss of hydrogen ions and chloride, resulting in metabolic alkalosis and hypochloremia. The body compensates by increasing bicarbonate reabsorption in the kidneys, which also leads to potassium loss, causing hypokalemia.
- Other Likely diagnoses
- C Primary hyperaldosteronism: This condition involves excessive production of aldosterone, leading to sodium retention, water retention, and potassium excretion. While it can cause hypokalemia and metabolic alkalosis, the presence of significant weight loss and the specific pattern of electrolyte imbalance (notably the very low urine chloride) makes it less likely than surreptitious vomiting.
- Do Not Miss (ddxs that may not be likely, but would be deadly if missed.)
- B Cushing syndrome: Although less likely given the patient's presentation, Cushing syndrome can cause weight gain rather than loss, hypertension, and hypokalemia due to the mineralocorticoid effects of excess cortisol. It's crucial to consider this diagnosis due to its potential severity and the need for specific treatment.
- Rare diagnoses
- A Bartter syndrome: This is a rare genetic disorder affecting the kidneys' ability to reabsorb sodium and chloride, leading to hypokalemia, metabolic alkalosis, and usually presents in childhood. The patient's age and the acute presentation of significant weight loss make this diagnosis less likely.