Low TIBC is seen in:
**Core Concept**
TIBC (Total Iron Binding Capacity) is a measure of all proteins available for binding mobile iron, including transferrin. Low TIBC indicates a reduced capacity for iron binding, which can be caused by various factors.
**Why the Correct Answer is Right**
A low TIBC is typically seen in conditions where there is an increased level of transferrin saturation, such as hemochromatosis or iron overload. In these cases, the body has enough iron-bound transferrin and doesn't require more transferrin to bind additional iron. This leads to a decrease in TIBC. Additionally, a low TIBC can also be seen in conditions where there is an increased level of ferritin, such as in cases of iron overload or hemochromatosis.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is often a distractor, as it might seem plausible due to the association between anemia and iron deficiency. However, a low TIBC is not typically seen in anemia of chronic disease, where iron is often already bound to transferrin, making it unavailable for erythropoiesis.
**Option B:** This option is incorrect because anemia due to iron deficiency typically presents with a high TIBC, as the body tries to capture more iron from the diet.
**Option C:** This option is incorrect because thalassemia major is a genetic disorder affecting hemoglobin production, and its diagnosis is not typically associated with changes in TIBC.
**Option D:** This option is incorrect because anemia of chronic disease often presents with a normal or high ferritin level, as the body tries to conserve iron.
**Clinical Pearl / High-Yield Fact**
A low TIBC can be seen in conditions where there is an increased level of transferrin saturation, such as hemochromatosis or iron overload. This is a key point to remember when interpreting laboratory results.
**Correct Answer: D. Anemia of chronic disease.**