PEORIA, Illinois (WEEK/Gray News) – The cause of death has been determined of an 8-year-old Missouri girl who suffered a medical emergency on a flight diverted to an Illinois city.

In June, Sydney Weston was traveling with her family when she suddenly became ill and unresponsive during the flight.

The Chicago-bound flight was diverted to Peoria. When the plane landed, Sydney was not breathing and had no pulse. Authorities immediately began life-saving measures and took Sydney to a hospital, where she was pronounced dead. Peoria County Coroner Jamie Harwood said Sydney’s death was caused by complications of chronic primary adrenalitis associated with multiple infections, including streptococcus and enteroviruses.

Weston also suffered from duodenitis, an inflammation of the first part of the small intestine, and thyroiditis, a general term for inflammation of the thyroid gland.

The three diagnoses indicate an underlying autoimmune disease, Harwood said. In an autoimmune disease, the immune system attacks healthy cells of organs and tissues, disrupting their normal function.

According to her obituary, Sydney was celebrating her 9th birthday in a week and had big plans for an ice skating party.

“We will always remember her for the joy she brought to everyone she met,” the obituary said. “Our hearts are heavy. She was our little girl and we celebrate her beautiful life.”

A GoFundMe campaign has been set up to help Sydney’s family pay for funeral expenses. As of Monday, more than $22,000 of the $25,000 goal had been raised.

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