Taylor Momsen is hospitalized with a “severe, potentially life-threatening throat infection,” her doctor tells Usmagazine.com. “I have been treating Miss Taylor Momsen for the last few days,” Dr. Shawn Nasseri tells Us. “She has been hospitalized for a severe, potentially life-threatening throat infection since Sunday. “She has been an excellent patient, and after aggressive antibiotics and medications, she is expected to make a full recovery in the next three to five days,” the doctor adds.

Momsen, 15, was in L.A. to take a school exam when she “woke up with a sore throat,” a source close to the actress tells Us. “She thought it was just a common cold, but was advised to see an ear, nose & throat specialist before getting on a plane back to New York,” the source adds. After discovering how serious the situation was, “her mom flew out to get her, and is flying back [to NYC] with Taylor this week. “She’s in unbelievable spirits” despite the diagnosis, the source says.