PDGFRA-associated chronic eosinophilic leukemia is a form of blood cell cancer characterized by an elevated number of cells called eosinophils in the blood. These cells help fight infections by certain parasites and are involved in the inflammation associated with allergic reactions. However, these circumstances do not account for the increased number of eosinophils in PDGFRA-associated chronic eosinophilic leukemia.

Another characteristic feature of PDGFRA-associated chronic eosinophilic leukemia is organ damage caused by the excess eosinophils. Eosinophils release substances to aid in the immune response, but the release of excessive amounts of these substances causes damage to one or more organs, most commonly the heart, skin, lungs, or nervous system. Eosinophil-associated organ damage can lead to a heart condition known as eosinophilic endomyocardial disease, skin rashes, coughing, difficulty breathing, swelling (edema) in the lower limbs, confusion, changes in behavior, or impaired movement or sensations. People with PDGFRA-associated chronic eosinophilic leukemia can also have an enlarged spleen (splenomegaly) and elevated levels of certain chemicals called vitamin B12 and tryptase in the blood.

Some people with PDGFRA-associated chronic eosinophilic leukemia have an increased number of other types of white blood cells, such as neutrophils or mast cells. Occasionally, people with PDGFRA-associated chronic eosinophilic leukemia develop other blood cell cancers, such as acute myeloid leukemia or B-cell or T-cell acute lymphoblastic leukemia or lymphoblastic lymphoma.

PDGFRA-associated chronic eosinophilic leukemia is often grouped with a related condition called hypereosinophilic syndrome. These two conditions have very similar signs and symptoms; however, the cause of hypereosinophilic syndrome is unknown.

PDGFRA-associated chronic eosinophilic leukemia is caused by mutations in the PDGFRA gene. This condition usually occurs as a result of genetic rearrangements that fuse part of the PDGFRA gene with part of another gene. Rarely, changes in single DNA building blocks (point mutations) in the PDGFRA gene are found in people with this condition. Genetic rearrangements and point mutations affecting the PDGFRA gene are somatic mutations, which are mutations acquired during a person's lifetime that are present only in certain cells. The somatic mutation occurs initially in a single cell, which continues to grow and divide, producing a group of cells with the same mutation (a clonal population).

The most common genetic abnormality in PDGFRA-associated chronic eosinophilic leukemia results from a deletion of genetic material from chromosome 4, which brings together part of the PDGFRA gene and part of the FIP1L1 gene, creating the FIP1L1-PDGFRA fusion gene.

The FIP1L1 gene provides instructions for a protein that plays a role in forming the genetic blueprints for making proteins (messenger RNA or mRNA).

The PDGFRA gene provides instructions for making a receptor protein that is found in the cell membrane of certain cell types. Receptor proteins have specific sites into which certain other proteins, called ligands, fit like keys into locks. When the ligand attaches (binds), the PDGFRA receptor protein is turned on (activated), which leads to activation of a series of proteins in multiple signaling pathways. These signaling pathways control many important cellular processes, such as cell growth and division (proliferation) and cell survival.

The FIP1L1-PDGFRA fusion gene (as well as other PDGFRA fusion genes) provides instructions for making a fusion protein that has the function of the normal PDGFRA protein. However, the fusion protein does not require ligand binding to be activated. Similarly, point mutations in the PDGFRA gene can result in a PDGFRA protein that is activated without ligand binding. As a result, the signaling pathways are constantly turned on (constitutively activated), which increases the proliferation and survival of cells. When the FIP1L1-PDGFRA fusion gene mutation or point mutations in the PDGFRA gene occur in blood cell precursors, the growth of eosinophils (and occasionally other blood cells, such as neutrophils and mast cells) is poorly controlled, leading to PDGFRA-associated chronic eosinophilic leukemia. It is unclear why eosinophils are preferentially affected by this genetic change.

Normal Function

The FIP1L1 gene provides instructions for making part of a protein complex named cleavage and polyadenylation specificity factor (CPSF). This complex of proteins plays an important role in processing molecules called messenger RNAs (mRNAs), which serve as the genetic blueprints for making proteins. The CPSF protein complex helps add a string of the RNA building block adenine to the mRNA, creating a polyadenine tail or poly(A) tail. The poly(A) tail is important for stability of the mRNA and for protein production from the blueprint.

Health Conditions Related to Genetic Changes

PDGFRA-associated chronic eosinophilic leukemia

A deletion of genetic material from chromosome 4 brings together part of the FIP1L1 gene and part of another gene called PDGFRA, creating the FIP1L1-PDGFRA fusion gene. This mutation is a somatic mutation, which means it is acquired during a person's lifetime and is present only in certain cells. This fusion gene causes PDGFRA-associated chronic eosinophilic leukemia, which is a type of blood cell cancer characterized by an increased number of eosinophils, a type of white blood cell involved in allergic reactions.

The FIP1L1-PDGFRA protein produced from the fusion gene has the function of the normal PDGFRA protein, which stimulates signaling pathways inside the cell that control many important cellular processes, such as cell growth and division (proliferation) and cell survival. Unlike the normal PDGFRA protein, however, the FIP1L1-PDGFRA protein is constantly turned on (constitutively activated), which means the cells are always receiving signals to proliferate. When the FIP1L1-PDGFRA fusion gene occurs in blood cell precursors, the growth of eosinophils (and occasionally other blood cells) is poorly controlled, leading to PDGFRA-associated chronic eosinophilic leukemia. It is unclear why eosinophils are preferentially affected by this genetic change.

Other Names for This Gene

• FIP1-like 1 protein
• FIP1_HUMAN
• hFip1
• pre-mRNA 3'-end-processing factor FIP1
• Rhe

Genomic Location

Normal Function

The PDGFRA gene provides instructions for making a protein called platelet-derived growth factor receptor alpha (PDGFRA), which is part of a family of proteins called receptor tyrosine kinases (RTKs). Receptor tyrosine kinases transmit signals from the cell surface into the cell through a process called signal transduction. The PDGFRA protein is found in the cell membrane of certain cell types where a specific protein, called platelet-derived growth factor, attaches (binds) to it. This binding turns on (activates) the PDGFRA protein, which then activates other proteins inside the cell by adding a cluster of oxygen and phosphorus atoms (a phosphate group) at specific positions (a process called phosphorylation). This process leads to the activation of a series of proteins in multiple signaling pathways.

The signaling pathways stimulated by the PDGFRA protein control many important cellular processes such as cell growth and division (proliferation) and cell survival. PDGFRA protein signaling is important for the development of many types of cells throughout the body.

Health Conditions Related to Genetic Changes

PDGFRA-associated chronic eosinophilic leukemia

Genetic abnormalities that involve the PDGFRA gene cause a type of blood cell cancer called PDGFRA-associated chronic eosinophilic leukemia. This condition is characterized by an increased number of eosinophils, a type of white blood cell involved in allergic reactions. These genetic abnormalities are somatic mutations, which are mutations acquired during a person's lifetime that are present only in certain cells. The most common of these genetic abnormalities is a deletion of genetic material from chromosome 4 that brings together parts of two genes, FIP1L1 and PDGFRA, creating the FIP1L1-PDGFRA fusion gene. Occasionally, genes other than FIP1L1 are fused with the PDGFRA gene. Mutations that change single DNA building blocks in the PDGFRA gene (point mutations) can also cause this condition, although these mutations are seen very rarely.

The protein produced from the FIP1L1-PDGFRA fusion gene (as well as other PDGFRA fusion genes) has the function of the PDGFRA protein. However, unlike the normal PDGFRA protein, the fusion protein does not require binding of the platelet-derived growth factor protein to be activated. Similarly, point mutations in the PDGFRA gene can result in a PDGFRA protein that is activated without ligand binding. As a result, the signaling pathways are constantly turned on (constitutively activated), which increases the proliferation and survival of cells. When the FIP1L1-PDGFRA fusion gene mutation or point mutations in the PDGFRA gene occur in early blood cells, the growth of eosinophils (and occasionally other blood cells) is poorly controlled, leading to PDGFRA-associated chronic eosinophilic leukemia. It is unclear why eosinophils are preferentially affected by this genetic change.

Gastrointestinal stromal tumor

Mutations in the PDGFRA gene are associated with gastrointestinal stromal tumors (GISTs). GISTs are a type of tumor that occurs in the gastrointestinal tract, most commonly in the stomach or small intestine. The majority of GISTs associated with a mutation in the PDGFRA gene occur in the stomach. In most cases, the genetic changes are acquired during a person's lifetime and are called somatic mutations. Somatic mutations, which lead to sporadic GISTs, are present only in the tumor cells and are not inherited. Less commonly, PDGFRA gene mutations that increase the risk of developing GISTs are inherited from a parent, which can lead to familial GISTs.

PDGFRA gene mutations associated with GISTs create a protein that no longer requires binding of the platelet-derived growth factor protein to be activated. As a result, the PDGFRA protein and the signaling pathways are constitutively activated, which increases cell proliferation and survival, leading to tumor formation.

Other disorders

PDGFRA gene mutations that lead to a constitutively active PDGFRA protein are also associated with inflammatory fibroid polyps, which are small, noncancerous (benign) tumors that form in the gastrointestinal tract. These tumors are made up of fibrous tissue and usually contain cells known to cause inflammation (inflammatory cells). As in GISTs, the constitutively active PDGFRA protein leads to the overgrowth of cells and formation of tumors.

Other Names for This Gene

• CD140 antigen-like family member A
• CD140A
• CD140a antigen
• GAS9
• PDGFR-alpha
• PDGFR2
• PGFRA_HUMAN
• platelet-derived growth factor receptor 2
• platelet-derived growth factor receptor alpha
• platelet-derived growth factor receptor, alpha polypeptide

Genomic Location

PDGFRA-associated chronic eosinophilic leukemia is not inherited and occurs in people with no history of the condition in their families. Mutations that lead to a PDGFRA fusion gene and PDGFRA point mutations are somatic mutations, which means they occur during a person's lifetime and are found only in certain cells. Somatic mutations are not inherited. Males are more likely to develop PDGFRA-associated chronic eosinophilic leukemia than females because, for unknown reasons, PDGFRA fusion genes are found more often in males.

PDGFRA-associated chronic eosinophilic leukemia is a rare condition; however, the exact prevalence is unknown.