Methemoglobinemia beta-globin (methemoglobinemia, beta-globin type) type - HBB gene.
Methemoglobinemia type beta-globin, is an inherited blood disorder in which the function of hemoglobin is interrupted. This alteration is characterized by increased concentrations of an abnormal form of hemoglobin that is unable to carry oxygen effectively. In most individuals with methemoglobinemia, beta-globin type, the only symptom is cyanosis, which gives a bluish appearance of the skin of the mucous membranes or the area under the nails due to lack of oxygen in the blood . In rare cases, methemoglobinemia beta-globin type can cause headaches, weakness and fatigue. Symptoms may appear at the age of 6 months. These symptoms do not improve when they are given additional oxygen to the individuals affected, because oxygen can not effectively bind to the abnormal hemoglobin.
This process is due to mutations in the gene HBB (hemoglobin subunit beta), located on the short arm of chromosome 11 (11p15.5), encoding the protein beta-globin. This protein is a subunit of hemoglobin, which is found inside the erythrocytes. Hemoglobin usually consists of four protein subunits, both subunits of beta-globin and two alpha globin subunits. Each of the four subunits of the hemoglobin molecule contains a called heme iron. Heme molecules are necessary for blood erythrocytes collect oxygen in the lungs and release the body 's cells. A complete protein hemoglobin is capable of carrying four oxygen molecules at a time, one with each heme. Oxygen bound to hemoglobin gives blood its bright red.
They have identified more than 10 mutations in the gene responsible for methemoglobinemia HBB type beta-globin. Often these mutations affect the region of the protein that binds to the heme. For hemoglobin binds oxygen, the iron within the heme molecule needs to be in a form called ferrous iron (Fe 2+). Iron within the heme can switch to another form of iron called ferric iron (Fe 3+), which can not bind oxygen. Hemoglobin containing ferric iron is known as methemoglobin and is unable to efficiently deliver oxygen to the body tissues. In methemoglobinemia type beta-globin, mutations in the gene HBB alter the protein beta-globin and cause the iron to ferric ferrous change. This alteration of hemoglobin in the blood gives a brown color and causes cyanosis. Signs and symptoms of methemoglobinemia beta-globin type are generally limited to cyanosis, which does not cause any health problems. However, in rare cases, it can cause headaches, weakness and fatigue.
Methemoglobinemia beta-globin type is inherited as an autosomal dominant, which means that a copy of the altered gene in each cell is sufficient to express the disease.
Tests in IVAMI: in IVAMI perform detection of mutations associated with methemoglobinemia beta-globin, type complete by PCR amplification of exons HBB gene, and subsequent sequencing.
Samples recommended: EDTA blood collected for separation of blood leukocytes, or impregnated sample card with dried blood (IVAMI may mail the card to deposit the blood sample).