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Ancestor membership does not transfer phenotype values between groups.","importantHtml":""},"sections":[{"bodyHtml":"<p>Variants (also called mutations) in the ALAS2 gene cause X-linked sideroblastic anemia. The ALAS2 gene provides instructions for making an enzyme called 5-aminolevulinate synthase. This enzyme is active in the bone marrow, where it plays a critical role in the production of heme (a component of hemoglobin).</p><p>ALAS2 gene variants lead to the production of a 5-aminolevulinate synthase enzyme that does not function properly. As a result, normal heme production is disrupted and red blood cells cannot make enough hemoglobin. Because most of the iron in red blood cells is normally used for heme, reduced heme production causes a buildup of iron in these cells. The body compensates by absorbing more iron from the diet, which leads to an accumulation of iron in the body&#x27;s organs. Low hemoglobin levels and iron accumulation lead to the characteristic features of X-linked sideroblastic anemia.</p><p class=\"section-source\"><a href=\"https://medlineplus.gov/genetics/condition/x-linked-sideroblastic-anemia/#causes\">MedlinePlus Genetics: Causes</a></p>","key":"forms","title":"What causes X-linked sideroblastic anemia?"},{"bodyHtml":"<p>The signs and symptoms of X-linked sideroblastic anemia are caused by a combination of too little hemoglobin and too much iron. Common signs and symptoms include extreme tiredness (fatigue), dizziness, a rapid heartbeat, pale skin, and an enlarged liver and spleen (hepatosplenomegaly). Over time, severe health problems such as heart disease and liver damage (cirrhosis), can result from the buildup of iron in these organs.</p><p>Males with X-linked sideroblastic anemia typically have the classic signs and symptoms of the condition, while females tend to be less severely affected. Females with X-linked sideroblastic anemia usually develop features of the condition in mid to late adulthood, while affected males often first experience symptoms in adolescence to early adulthood.</p><p class=\"section-source\">Source: <a href=\"https://medlineplus.gov/genetics/condition/x-linked-sideroblastic-anemia\">MedlinePlus Genetics</a></p>","key":"overview","title":"Condition overview"}],"sharedSources":[],"slug":"x-linked-sideroblastic-anemia","sourceDocuments":[{"name":"X-linked sideroblastic anemia","reviewed":"2025-09","sections":{"causes":{"fetchedAt":"2026-10-20T20:26:00.315716+00:00","label":"Causes","pageSha256":"d0449fd1a6dc93a0cc72c7ffbaa35584904cb778b6d85171738e483168dcc6fa","sourceUrl":"https://medlineplus.gov/genetics/condition/x-linked-sideroblastic-anemia/#causes","status":"available"}},"source_release":"2026-10-01","url":"https://medlineplus.gov/genetics/condition/x-linked-sideroblastic-anemia"}],"sourceNote":"MedlinePlus descriptions and Causes; original HPO annotations.","takeawayHtml":"Cause explanations are from MedlinePlus Genetics. Feature values below retain their original sources and patient groups.","title":"X-linked sideroblastic anemia"},"schemaVersion":1}