What is the most likely diagnosis for a 25-year-old woman at 24 weeks gestation with elevated blood pressure, proteinuria, headache, and ankle swelling?

The most likely diagnosis for the 25-year-old woman at 24 weeks of gestation, presenting with elevated blood pressure, proteinuria, headache, and ankle swelling, is preeclampsia.

Preeclampsia is characterized by the new onset of hypertension and proteinuria after the 20th week of gestation. The combination of elevated blood pressure and proteinuria is a hallmark of this condition. In this scenario, the presence of symptoms such as headache and ankle swelling further supports the diagnosis. The headache may be due to increased blood pressure, and swelling can be a typical finding in pregnancy, but when associated with hypertension and proteinuria, it raises concern for preeclampsia.

A diagnosis of HELLP syndrome, while it can occur in the context of preeclampsia, typically presents with more severe symptoms, including liver enzyme elevations and hemolytic anemia, not solely with the combination of proteinuria, swelling, and headache. Gestational hypertension is characterized by elevated blood pressure without the presence of proteinuria. Refractory hypertension can occur, but it does not encompass the specific triad of hypertension, proteinuria, and additional symptoms like headache that are indicative of preeclampsia.

Thus,