Actor Eric Dane was misdiagnosed with a treatable illness months before receiving his amyotrophic lateral sclerosis (ALS) diagnosis, according to details from his upcoming memoir, "My Book Of Days: A Memoir of Moments." The book, released Tuesday, recounts Dane's health struggles, addiction, and his relationship with ex-wife Rebecca Gayheart.

Dane first sought medical attention for a gradual loss of function in his right hand. He was initially evaluated by hand specialists who referred him to a neurologist. This neurologist suspected neuropathy but felt the condition was beyond his expertise and referred Dane to another doctor. Dane described a lengthy process of seeing multiple doctors and undergoing various tests, including an EMG, which eventually led to a consensus diagnosis of multifocal motor neuropathy. He was told this condition had a treatment that was 90 percent effective.

However, the prescribed treatment, an injection of immunoglobulin, did not work, leaving Dane unable to move his right hand. His physicians became concerned, and Dane himself grew worried. He returned to his primary care physician, who informed him that doctors had been discussing ALS but needed to wait for further developments. This led to several months of additional testing, including a lumbar puncture, spinal fluid extraction, and brain scans, none of which provided a diagnosis.

Frustrated, Dane sought a second opinion from Dr. Terrelonge, the head of neurology at the University of California, San Francisco. Dr. Terrelonge confirmed Dane's fear: the diagnosis was ALS. Dane described the moment as hearing a "death sentence," understanding it meant a progressive, degenerative disease that would impair his ability to walk, use his hands, speak, and breathe.

Dane, known for his role as Dr. Mark Sloan on "Grey's Anatomy," died on February 19 at age 53, approximately a year after announcing his ALS diagnosis. He and actress Rebecca Gayheart, with whom he shares daughters Billie and Georgia, had divorced in 2017 but later called off their divorce proceedings before Dane revealed his illness. Gayheart remained a supportive figure throughout his final year.

The memoir "My Book Of Days: A Memoir of Moments" is now available.