Causes
Typical causes of microcytic anemia include:

Childhood
Iron deficiency anemia by far the most common cause of anemia in general and of microcytic anemia in particular
Thalassemia
Adulthood
Iron deficiency anemia
Thalassemia
Anemia of chronic diseaseRare hereditary causes of microcytic anemia include sideroblastic anemia and other X-linked anemias, hereditary hypotransferrinemia, hereditary aceruloplasminemia, erythropoietic protoporphyria, iron-refractory iron deficiency anemia, and other thalassemic mutations (such as hemoglobin E and hemoglobin Lepore syndrome).Rare acquired causes of microcytic anemia include lead poisoning, zinc deficiency, copper deficiency, alcohol, and certain medications.Other causes that are typically thought of as causing normocytic anemia or macrocytic anemia must also be considered, as the presence of two or more causes of anemia can distort the typical picture. Iron Deficiency Anemia
Nearly half of all anemia cases are due to iron deficiency as it is the most common nutritional disorder. Although it is a common nutritional disorder, most causes of iron deficiency anemia (IDA) are due to blood loss. It is also more common to occur among children and females who are menstruating but can occur to any individual of any age. As well as a low MCV, diagnostic criteria includes low serum ferritin levels and transferrin saturation may also be used. Non-pharmacological measures to treat IDA include increasing sources of dietary iron, especially from heme sources such are liver, seafood, and red meats. However, these measures often take a great deal of time longer to replete iron stores compared to pharmacological agents such as iron supplements which are the mainstay of treatment.
In some cases there may be a rudimentary rib or a cervical rib that can be causing the compression, which can be removed using the same technique.Physical therapy is often used before and after the operation to improve recovery time and outcomes. Potential complications include pneumothorax, infection, loss of sensation, motor problems, subclavian vessel damage, and, as in all surgeries, a very small risk of permanent serious injury or death. Notable cases
SportsSeveral Major League Baseball players, especially pitchers, have been diagnosed with thoracic outlet syndrome, including Stephen Strasburg, Chris Archer, Matt Harvey, Chris Carpenter, Jaime Garcia, Shaun Marcum, Matt Harrison, Clayton Richard, Nate Karns, and Noah Lowry. Starting pitcher Chris Young, who previously struggled with shoulder problems, underwent surgery for TOS in 2013 and felt "completely different" post-recovery. Young exceeded expectations on his return to the major leagues at age 35, becoming a valuable member of the 2014 Seattle Mariners starting rotation. In July 1980, Houston Astros starting pitcher J.R. Richard collapsed while playing a game of catch, and was found to have experienced a stroke due to severe blockage of his right carotid artery. Given the fact that shortly beforehand, he had been found to have near-total obstruction of the arteries supplying his right arm, he was eventually diagnosed with extensive arterial thoracic outlet syndrome. Although he attempted a comeback, his professional baseball career was effectively ended.NHL defenseman Adam McQuaid was diagnosed with TOS in September 2012, and as a result was nominated for the Bill Masterton Memorial Trophy.