LOS ANGELES, CALIFORNIA: Acute myelogenous leukemia (AML), a cancer of the bone marrow, has been confirmed as Paul Reubens’ cause of death. The news comes a month after the ‘Pee-wee Herman Show’ star's demise.

AML, is also referred to as acute granulocytic leukemia, acute nonlymphocytic leukemia, acute myeloid leukemia, and acute myeloblastic leukemia, affects the spongy tissue found inside bones, where blood cells are created.

The primary cause of Paul Reubens' death was revealed to be AML only after the actor's death certificate was made public, as reported by the Blast.

Reubens was reportedly also facing metastatic lung cancer, which spread to the other lung or other body organs.

Paul Reubens kept his cancer diagnosis a secret for many years before passing away on July 30 at the age of 70.

Acute myelogenous leukemia affects a group of white blood cells

AML is referred to as myelogenous leukemia because it affects a fraction of white blood cells known as myeloid cells. These typically mature into other types of mature blood cells such as red blood cells, white blood cells, and platelets.

In acute myelogenous leukemia, the word "acute" refers to the disease's rapid growth, as per Mayo Clinic.

It is an aggressive malignancy that, if left untreated, can prove fatal. AML primarily affects persons over the age of 60, while it can also affect children and younger adults. People with AML are now living longer due to new medicines.

Paul Reuben left posthumous apology to his fans

Reubens had issued a posthumous apology at the time of his death for keeping his cancer fight a secret from the public.

Reubens wrote before his death: "Please accept my apology for not going public with what I’ve been facing the last six years. I have always felt a huge amount of love and respect from my friends, fans and supporters. I have loved you all so much and enjoyed making art for you."

What are the symptoms that Paul Reuben experienced?

Reuben's in the early-stages of the disease would have experienced AML's general signs and symptoms that can resemble those of the flu or other common illnesses.

Acute myelogenous leukemia symptoms include fever, breathing difficulty, bone ache, fatigue and lethargy, pale skin, frequent infections, mild bruising, and abnormal bleeding, such as frequent nosebleeds and gum bleeding.

The exact cause of acute myeloid leukemia is unknown. Experts are, however, aware that the disease is caused by specific genes or chromosomes that mutate (alter), leading to abnormal blood cells.

AML develops when a bone marrow cell experiences alterations (mutations) in its DNA or genetic makeup. The signals that inform a cell what to do are encoded in its DNA.

Myeloblasts, leukemic white blood cells, are formed from immature cells that are produced in the bone marrow. These aberrant cells can accumulate and suffocate healthy cells since they cannot function normally.

Paul Reubens' metastatic lung cancer worsened his condition

While the primary cause of death listed on actor Reubens' death certificate was "acute myelogenous leukemia," the actor unfortunately also battled metastatic lung cancer in the months before his death.

The death certificate for the 'Pee-wee's Playhouse' alumnus further stated that he died from "acute hypoxic respiratory failure," which was most likely brought on by the lung cancer.

According to reports, Reubens was cremated and will be buried in the Hollywood Forever Cemetery.