A 20-year-old woman presents with fatigue and pale skin. What condition is she most likely suffering from?

The presentation of fatigue and pale skin in the 20-year-old woman is strongly suggestive of iron-deficiency anemia. This condition is marked by insufficient iron levels in the body, leading to a decreased production of hemoglobin, which is crucial for transporting oxygen in the blood. Symptoms such as fatigue result from reduced oxygen delivery to tissues, while pale skin is a common external sign due to lower levels of red blood cells.

Iron-deficiency anemia is particularly prevalent among young women, often due to factors such as menstrual blood loss and dietary insufficiencies. The iron requirements increase during menstruation, and if dietary intake does not meet the increased needs, it may lead to a deficiency.

In contrast, other options present different underlying mechanisms. Pernicious anemia involves a deficiency in vitamin B12 due to intrinsic factor deficiency, while megaloblastic anemia is also related to issues with B12 or folate but presents specific macrocytic cells on a blood smear. Iron overload signifies an excess of iron in the body, which does not align with the symptoms described. Therefore, the combination of fatigue and pale skin in this scenario aligns most closely with iron-deficiency anemia as the underlying condition.