After struggling for years with the infection, MacDonald said it eventually turned to sepsis, causing his fingers, toes, and eventually his penis to turn black.
"It was like a horror film. I was in a complete panic. I knew deep down it was gone and I was going to lose it," he said. "Then one day it just dropped off on to the floor."
"Because I had been through the devastation of knowing I was going to lose it, I just picked it up and put it in the bin," he explained.
He said his life fell apart as he slipped into a depression, and started drinking heavily — until his doctor told him about Professor David Ralph, an expert in penis construction.
After consulting with him, MacDonald loved everything he heard, with one small added request: an extra two inches in length. "They were happy to listen to what I wanted it to be like, which was amazing," he said, "Not many can say they have a designer penis."
Surgeons took a flap of skin from his left arm and rolled it into a "penis", complete with its own blood vessels and nerves. They installed a urethra, as well as two special tubes that could be inflated via hand pump, to allow him on-demand erections.
They then detached most of the shaft from the arm, leaving it dangling from its base, to allow it form naturally.
"When I saw it on my arm for the first time I was so, so proud," he told the publication. "After everything I had been through it didn't feel weird at all - it was just a part of me. I was like any other man, I just couldn't leave it alone to begin with. I thought it was the best thing ever."
MacDonald was told it would have to stay on his arm for two years, a sacrifice he was more than willing to make. He said people would ask to see it and sometimes make fun — and he saw the funny side too.
"But I get it. It's not every day you see a man with a penis on his arm. Of course I see the funny side - I have to. I don't have any other option," he said. "If I couldn't laugh at the willy on my arm I'd be finished."
But when the time came for it to finally take its rightful place in 2018, he fell ill and had to miss the surgery; a subsequent string of scheduling mix-ups and transport issues nixed more dates, while a hospital staff shortage last December postponed the surgery at the 11th hour once again.
Then, COVID-19 arrived.
"The delays have been hard to deal with. For one reason and another the final operation has never happened," he said. "It feels like I'm cursed sometimes."
He hopes to finally put Jimmy in his place by the end of the year.
"It really feels like it is time to get it off," he said. "I can't run because it waggles about. I can't go swimming or wear a short-sleeve shirt.
"I can't lie, having a penis on your arm for four years is a really strange thing to live with," he added. "But I am determined this penis will be ultimately used for what it was built for."
A spokesperson for University College Hospital London told The Sun it is working on a new surgery date as soon as possible: "We understand this is a distressing situation for Mr. MacDonald."