An open letter from Charlie Sheen:

Roughly four years ago, I suddenly found myself in the throws of a seismic and debilitating three-day cluster-migraine-like headache. I was emergently hospitalized with what I believed to be a brain tumor or perhaps some unknown pathology. I was partially correct. Following a battery of endless tests, that included a hideous spinal tap, it was sadly and shockingly revealed to me that I was, in fact, positive for HIV.

The news was a "mule kick" to my soul. Those impossible words I absorbed and then tried to convince myself, that I was stuck, suspended, or even stranded inside some kind of alternate reality or nightmare, were to the absolute contrary. I was awake. It was true… reality.

Under the brilliant and perfect care of Dr. Robert Huizenga as well as “the” leading infectious disease expert in the known universe, I began a rigorous and intensive treatment program. Not missing a beat, a med dose, or one shred of guidance, quickly my viral loads became undetectable. Like every other challenge in my life, again, I was victorious and kicking this disease’s ass. I wish my story had ended there. Unfortunately, for my family and myself, it had only just begun.

The personal disbelief, karmic confusion, shame and anger lead to a temporary yet abysmal descent into profound substance abuse and fathomless drinking. It was a suicide run. Problem was, I’d forgotten that I’m too tough for such a cowardly departure. Yet, despite this loathsome and horrific odyssey, I was vigilant with my anti-viral program.

WATCH: Charlie Sheen reveals he's HIV positive in TODAY exclusive

My medical team could only shake their heads as each and every blood test returned levels revealing a state of remission. Even though I might have been trying to kill myself, one thing was radically evident; the disease was not.

In and around this perplexing and difficult time, I dazedly chose (or hired) the companionship of unsavory and insipid types. Regardless of their salt-less reputations, I always lead with condoms and honesty when it came to my condition. Sadly, my truth soon became their treason, as a deluge of blackmail and extortion took center stage in this circus of deceit.

To date, I have paid out countless millions to these desperate charlatans.

Locked in a vacuum of fear, I chose to allow their threats and skulduggery to vastly deplete future assets from my children, while my “secret” sat entombed in their hives of folly (or so I thought).

News Flash: This ends today. I’m claiming back my freedom. The scales of justice will swiftly and righteously re-balance themselves.

In conclusion, I accept this condition not as a curse or scourge, but rather as an opportunity and a challenge. An opportunity to help others. A challenge to better myself.

Every day, of every month, of every year, countless individuals go to work, man their stations, fulfill their professional obligations with a host of disabilities. Diseases, imperfections, hurdles, detours. These maladies range from lupus to cancer, from paralysis to blindness, from diabetes to obesity. “Treated,” HIV is no different.

My partying days are behind me. My philanthropic days are ahead of me.

Ernest Hemingway once wrote, “Courage is grace under pressure.”

I’ve served my time under pressure; I now embrace the courage, and the grace.

Love and peace,Charlie Sheen

-----------------------------------------

Statement from Dr. Robert Huizenga, Associate Clinical Professor of Medicine, UCLA

Four years ago, Charlie Sheen came to see me with an upper viral infection followed by joint aches, swallowing complaints and then progressive severe headaches. During this infection, his HIV tests "seroconverted" (acutely changed) from negative to positive. He was immediately placed on four antiretroviral drugs and his HIV viral blood levels thankfully dropped to undetectable. He has tolerated his antiretroviral cocktail and by faithfully complying with the daily pills, his viral HIV load has remained consistently undetectable.

Charlie Sheen discusses his HIV-positive diagnosis Tuesday on TODAY. Samantha Okazaki / Samantha Okazaki / TODAY

The urgent dilemma that both Charlie and I recognize is that there are 1.2 million other Americans currently living with this diagnosis. Shockingly, up to 20 percent of these individuals are unaware of their HIV status and sadly 60 percent are not adequately being treated. This leads to 50,000 new diagnoses and 18,000 HIV deaths yearly in this country.

I anticipate Charlie can save many more lives coming forward with his revelation than I could ever have aspired to as a doctor. With Charlie remaining dedicated to his treatment regimen, I expect the HIV will only minimally — if at all — affect his predicted life expectancy.