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Thalassemia Thalassemias are inherited disorders caused by mutations in globin genes that decrease the synthesis of α- or β-globin. Decreased synthesis of one globin results not only in a deficiency of Hb but also in red cell damage that is caused by precipitates formed from excess unpaired "normal" globin chains. The mutations that cause thalassemia are particularly common in Mediterranean, African, and Asian regions in which malaria is endemic. As with HbS, it is hypothesized that globin mutations associated with thalassemia protect against falciparum malaria. Pathogenesis A diverse collection of α-globin and β-globin mutations underlies the thalassemias, which are autosomal codominant conditions. Adult hemoglobin (HbA) is composed of two α chains and two β chains. α chains are encoded by two α-globin genes on chromosome 16. β chains are encoded by a single β-globin gene on chromosome 11. Clinical features vary widely depending on the combination of mutated alleles inherite...

What is Polymyositis? Polymyositis is a rare, chronic inflammatory muscle disease that causes muscle weakness , particularly in the muscles closest to the trunk of the body , such as the shoulders, hips, and thighs. It is classified as an idiopathic inflammatory myopathy (IIM) , meaning its exact cause is unknown and it involves immune system-related muscle inflammation. Key Features of Polymyositis Symmetrical muscle weakness : Both sides of the body are affected equally. Progressive condition : Symptoms develop slowly over time. Primarily affects adults : Most common between ages 30 and 60. More common in women than in men. Causes and Risk Factors The exact cause of polymyositis is unknown, but it is considered an autoimmune disorder , where the body's immune system mistakenly attacks healthy muscle tissue. Possible triggers include: Viral infections Genetic predisposition Autoimmune reactions Other connective tissue diseases (e.g., lupus, rheuma...