Iron Deficiency Anemia: Elevated RDW (Red Cell Distribution Width) indicates a variation in red blood cell size, which is common in iron deficiency anemia. Low ferritin levels confirm depleted iron stores, and low iron levels further support this diagnosis. Iron deficiency anemia is the most common cause of anemia and can result from inadequate iron intake, increased iron requirement, or chronic blood loss.

Chronic Disease Anemia: Conditions like chronic kidney disease, rheumatoid arthritis, or chronic infections can lead to anemia of chronic disease, which may present with low iron and ferritin levels due to inflammation-induced hepcidin elevation, leading to sequestration of iron.
Anemia of Chronic Kidney Disease: This condition can lead to a decrease in erythropoietin production, affecting red blood cell production. Although ferritin might be low, indicating iron deficiency, it's also possible for ferritin to be elevated as an acute-phase reactant in chronic diseases.
Thalassemia Trait: While not directly related to iron and ferritin levels, thalassemia trait can cause microcytic anemia with an elevated RDW due to the variability in red blood cell size. However, iron and ferritin levels might be normal or slightly elevated due to increased iron absorption.

Celiac Disease: This autoimmune disorder can lead to malabsorption of iron and other nutrients, resulting in iron deficiency anemia. It's crucial to consider celiac disease, especially if there are gastrointestinal symptoms or a family history.
Gastrointestinal Bleeding: Chronic, occult gastrointestinal bleeding can lead to iron deficiency anemia. Identifying and treating the source of bleeding is critical to prevent serious complications.
Malignancy: Certain cancers, particularly gastrointestinal cancers, can cause iron deficiency anemia due to chronic blood loss or malabsorption. Although less common, malignancy is a critical diagnosis not to miss.

Pregnancy-Related Anemia: During pregnancy, the demand for iron increases significantly. If this demand is not met, it can lead to iron deficiency anemia. Although not rare in the context of pregnancy, it's less likely in the general population.
Hemoglobinopathies: Other than thalassemia, other hemoglobinopathies can affect red blood cell production and size, potentially leading to an elevated RDW. However, these conditions are less common and often have distinct clinical and laboratory features.
Sideroblastic Anemia: A group of disorders characterized by the presence of ringed sideroblasts in the bone marrow, which can be congenital or acquired. This condition can lead to microcytic anemia but is relatively rare.