Leukemia
Synonyms and keywords: Leukaemia

# Overview
Leukemia (Greek leukos, white; haima, blood) can be defined as a group of hematopoietic stem cell malignancies due to genetic abnormalities that may lead to clonal proliferation of these cells. These group of diseases are classified based on the type of hematopoietic stem cell involved and the duration of the disease. The leukemias are the most common malignancies among children younger than 15 years. Among them, Acute Lymphoblastic Leukemia (ALL) is the most common leukemia and accounts for 77% of childhood leukemia. However, Chronic Lymphocytic Leukemia (CLL) is the most common form of leukemia in adults, and it accounts for 30% of all leukemias in the United States. The increased rate of proliferation and decreased rate of apoptosis in this progeny of cells may compromise normal bone marrow function and ultimately result in marrow failure. Clinical manifestations, diagnosis, laboratory findings, and therapy are different according to the type of malignancy.

# Classification
Leukemia may be classified as follows:

# Differentiating Leukemia from other Diseases
Leukemia must be differentiated from various diseases that cause weight loss,  night sweats, hepatosplenomegaly, and palpable lymph nodes, such as hairy cell leukemia, prolymphocytic leukemia, follicular lymphoma, and mantle cell lymphoma. Based on the expression of cell surface markers, the table below differentiates different types of leukemia from other diseases that cause similar clinical presentations:

# Epidemiology and Demographics

## Prevalence
- In the United States, the age-adjusted prevalence of leukemia is 75.3 per 100,000 in 2011.

## Incidence
- The delay-adjusted incidence of leukemia in 2011 was estimated as 15.48 per 100,000 individuals in the United States.
- In 2011, the age-adjusted incidence of leukemia was 13.66 per 100,000 individuals in the United States.

## Age
- The overall age-adjusted incidence of leukemia in the United States between 2007 and 2011 was 13 per 100,000 occurrences. The age-adjusted incidence of leukemia by age category is:
Under 65 years: 6.5 per 100,000
65 and over: 57.9 per 100,000
- Under 65 years: 6.5 per 100,000
- 65 and over: 57.9 per 100,000
- Shown below is a table depicting the overall age-adjusted incidence of leukemia per 100,000 individuals by age in the United States between 2007 and 2011 for the different types of leukemia.

## Gender
- In the United States, the age-adjusted prevalence of leukemia by gender in 2011 was:
In males: 92.7 per 100,000
In females: 60.7 per 100,000
- In males: 92.7 per 100,000
- In females: 60.7 per 100,000
- In the United States, the delay-adjusted incidence of leukemia by gender in 2011 was:
In males: 19.93 per 100,000 persons
In females: 11.89 per 100,000 persons
- In males: 19.93 per 100,000 persons
- In females: 11.89 per 100,000 persons
- In the United States, the age-adjusted incidence of leukemia by gender on 2011 was:
In males: 17.58 per 100,000 persons
In females: 10.49 per 100,000 persons
- In males: 17.58 per 100,000 persons
- In females: 10.49 per 100,000 persons
- Shown below is an image depicting the delay-adjusted incidence and observed incidence of leukemia by gender and race in the United States between 1975 and 2011. These graphs were gathered from SEER: The Surveillance, Epidemiology, and End Results Program of the National Cancer Institute.

## Race
- Shown below is a table depicting the age-adjusted prevalence of leukemia by race in 2011 in the United States.
- Shown below is an image depicting the incidence of leukemia by race in the United States between 1975 and 2011.
API: Asian/Pacific Islander; AI/AN: American Indian/ Alaska Native

# Prognosis

## 5-Year Survival
- Between 2004 and 2010, the 5-year relative survival of patients with leukemia was 60.3%.
- When stratified by age, the 5-year relative survival of patients with leukemia was 68.5% (44.1% for patients <65 and  65 years of age respectively).
- Shown below is a table depicting the 5-year relative survival of patients by the type of leukemia in the United States between 2004 and 2010.