Arnaz was just 22 and getting a picture of his future when he received jarring news

Desi Arnaz was terrified when a misdiagnosis led him to believe he was dying.

In the re-release of his memoir, A Book: The Outspoken Memoirs of the Man Who “Loved Lucy”—and Revolutionized Television, Arnaz discusses his single life before falling for Lucille Ball.

It wasn’t his love life that led to his medical mishap, however. Arnaz sought medical attention after noticing pain in his foot and a blue appearance. He was treated, all the while performing shows in between. As he recovered, his doctor shared another bit of news with the entertainer, diagnosing him with syphilis.

He recalled the doctor explaining, “I had to test your blood because of the poison in your foot, and the test showed that you have syphilis.”

The moment was jarring for Arnaz, who was just 22 and seeing his first signs of success in his career.

“I was twenty-two years old. The show was a big hit, but it hadn’t even gotten to Broadway yet. And this doctor was sitting there in front of me, telling me I had syphilis,” he wrote, noting, “In those days, that was worse than death. There was no penicillin cure yet—nothing.”

At this point, Arnaz was already rehearsing on Richard Rodgers and Lorenz Hart’s Too Many Girls and was determined not to lose the gig. Still, he struggled with feeling like his time was limited just as he was getting his big break.

“Strange how many things go through your mind at a time like that: You are 22, you’ve gone through 5 years of cleaning birdcages, gone hungry, worked at ratholes, the terrible things my father and mother had to go through in Cuba, and now I’m in a successful show, about to open on Broadway, a show which the newspapers say will be a big fat hit and it looks as if I’ll be a hit too. A big fat hit on Broadway! And this man tells me I’ve got syphilis!” he continued.

Arnaz knew of just one person with syphilis — Al Capone, father of his high school friend Al Capone Jr. Knowing his fate, he begged for another test. Ultimately, those results were negative.

“If I have ever thanked God in my life, I thanked Him then. What had happened (I found out later) was this: When they took a blood test in a hospital, if you were a bed patient, they brought a tray with a lot of little glass tubes on it, and the boys from the lab took the blood and put it in one of those tubes. Then they put the name of the patient on the tube. I was not in a private room. So they had also taken blood from the patient next to me, confused the tubes and put my name on his blood test,” he explained.

The mix-up instilled a fear in him, however. He admitted, “For the next year and a half, I had a blood test taken every six months. I wouldn’t trust any hospital. I would go right to the doctor and say, ‘You take the blood in front of me, you put it in that little glass tube in front of me, and I’m going to take it to the lab myself, or if someone else has to take it, I’ll go with him.’ “