Actress Michelle Trachtenberg died of diabetes complications

Michelle Trachtenberg, the "Buffy the Vampire Slayer" and "Gossip Girl" actress who was discovered dead in a Manhattan apartment in February, died of diabetic complications, the New York City medical examiner's office announced on Wednesday.

Trachtenberg's death was first ruled unknown when the family opposed to an autopsy, but the medical examiner changed the diagnosis and manner of death based on laboratory data. The manner was found to be natural.

The New York Police Department responded to a 911 call at 8:01 a.m. local time on February 26 to an apartment in midtown Manhattan, where they discovered Trachtenberg unconscious and unresponsive. Trachtenberg was 39 years old.

Trachtenberg's unexpected demise astounded many who were unaware she had been coping with medical troubles. The actor had recently received a liver transplant.

Diabetes, commonly known as diabetes mellitus, is a chronic condition in which a person's blood sugar levels are abnormally high and the pancreas fails to generate adequate insulin. Complications of the condition, such as cardiovascular disease or renal failure, can cause mortality.

Trachtenberg began appearing in advertisements at the age of three. Before she was ten, she was a regular on Nickelodeon's sitcom "The Adventures of Pete & Pete" and ABC's daytime soap "All My Children."

Trachtenberg's breakthrough part occurred at the age of 11 in the 1996 film "Harriet the Spy." She went on to star in scores of television shows and films, including "Buffy the Vampire Slayer," as Buffy's sister, Dawn, and "Gossip Girl," as Georgina Sparks.

Many former Trachtenberg cast members paid tribute to their co-star following her passing in February, including Rosie O'Donnell, who described it as "heartbreaking."