Which condition is characterized by proteinuria greater than 300 mg in a 24-hour urine sample?

Preeclampsia is characterized by new-onset hypertension and proteinuria after 20 weeks of gestation. Specifically, the diagnosis of preeclampsia is made when there is proteinuria of greater than 300 mg in a 24-hour urine collection, along with elevated blood pressure. This condition typically arises during pregnancy and can lead to serious complications if not managed properly.

While mild and severe preeclampsia are related terms, the specific threshold of 300 mg in proteinuria aligns directly with the general diagnosis of preeclampsia, rather than distinguishing between mild and severe forms. Severe preeclampsia is often defined by higher blood pressure readings and additional symptoms such as multi-organ dysfunction, but the fundamental requirement for proteinuria exceeds 300 mg is first established with the diagnosis of preeclampsia itself. Eclampsia, on the other hand, refers to the occurrence of seizures in a patient with preeclampsia and does not focus solely on the proteinuria measurement.

Therefore, the correct answer, indicating the condition predominantly characterized by proteinuria greater than 300 mg in a 24-hour urine sample, is preeclampsia.