The calreticulin gene, called CALR for short, is responsible for making a protein called calreticulin. The exact function of calreticulin protein remains largely unknown, but it is likely involved in ensuring the correct folding of new proteins, maintaining correct calcium levels in cells, and a number of other cell functions. Mutations of the CALR gene are associated with bone marrow neoplasms that cause the production of too…The calreticulin gene, called CALR for short, is responsible for making a protein called calreticulin. The exact function of calreticulin protein remains largely unknown, but it is likely involved in ensuring the correct folding of new proteins, maintaining correct calcium levels in cells, and a number of other cell functions. Mutations of the CALR gene are associated with bone marrow neoplasms that cause the production of too many blood cells. These blood disorders are collectively known as myeloproliferative neoplasms (MPNs). The CALR mutation test looks for abnormalities in the CALR gene to help diagnose and classify MPNs. The MPNs most commonly associated with CALR mutations are:Essential thrombocythaemia (ET)—there are too many platelet-producing cells (megakaryocytes) in the bone marrow Primary myelofibrosis (PMF), also known as chronic idiopathic myelofibrosis—there are too many platelet-producing cells and cells that produce scar tissue in the bone marrow CALR mutations are the second most common genetic abnormality (after JAK2 mutations) associated with essential thrombocythaemia or primary myelofibrosis. They are present in about 20-25% of adults with ET and 25-30% of adults with PMF. Although rare and not well understood in children, 50% of paediatric PMF patients had CALR mutations. The CALR mutation is acquired after birth as opposed to inherited. It is caused by the addition or removal of small amounts of genetic material to a region of the gene called exon 9. This leads to an abnormal calreticulin protein. It is not yet understood how the mutant protein leads to signs and symptoms of MPN. While more than 50 types of CALR mutation have been found, only the two most common variants associated with MPNs are included in conventional PCR testing. Next generation sequencing (NGS)-based analysis should detect all mutation variants but is not widely available. In addition to helping diagnose MPNs, CALR mutation testing can provide information about a person’s prognosis. Studies have shown that compared to individuals with the JAK2 mutation, those with the CALR mutation had a milder disease course, fewer signs and symptoms of blood clotting (thrombotic episodes), and better survival. How is the sample collected for testing?A blood sample is obtained by inserting a needle into a vein in the arm. Sometimes a bone marrow aspiration and biopsy may be done to collect a sample for testing. Is any test preparation needed to ensure the quality of the sample?No test preparation is needed. See MoreSee Less
