Differential Diagnosis

The patient's laboratory findings show a low hemoglobin level, decreased hematocrit, and microcytic anemia (indicated by a mean corpuscular volume of 75 μm3). The serum iron level is low, while the total iron-binding capacity (TIBC) is elevated, and ferritin is low. These findings suggest iron deficiency anemia. Considering the patient's symptoms and laboratory results, the differential diagnosis can be categorized as follows:

• Single most likely diagnosis

  • A) Chronic inflammation secondary to rheumatoid arthritis: This is the most likely cause of the patient's laboratory findings. Chronic inflammation can lead to anemia of chronic disease, which is characterized by low serum iron, elevated ferritin, and a normocytic or microcytic anemia. However, in this case, the low ferritin level suggests iron deficiency anemia, which can also occur in the context of chronic inflammation due to rheumatoid arthritis, where the body's iron is not utilized effectively due to the inflammation.

• Other Likely diagnoses

  • C) Gastrointestinal bleeding secondary to ibuprofen: Long-term use of nonsteroidal anti-inflammatory drugs (NSAIDs) like ibuprofen can cause gastrointestinal bleeding, leading to iron deficiency anemia. The patient's use of ibuprofen makes this a plausible cause.
  • B) Folic acid deficiency: Although less likely given the microcytic anemia (folic acid deficiency typically causes macrocytic anemia), it's still a consideration, especially if the patient has a poor diet or malabsorption issues.

• Do Not Miss (ddxs that may not be likely, but would be deadly if missed.)

  • Gastrointestinal malignancy: Although not directly suggested by the information provided, any cause of iron deficiency anemia, especially in an elderly patient, warrants consideration of a gastrointestinal malignancy as a potential source of chronic blood loss.
  • Other chronic blood loss sources: These could include menstrual bleeding in premenopausal women, though this patient is 70, or other less common sources of chronic blood loss.

• Rare diagnoses

  • D) Methotrexate toxicity: Methotrexate can cause bone marrow suppression, leading to anemia, but this would typically be associated with other cytopenias (low white blood cell and platelet counts) and is less likely given the specific laboratory findings of iron deficiency anemia.
  • E) Normal aging: Anemia is not a normal part of aging, so while age can affect the prevalence and presentation of certain diseases, it is not a diagnosis for the patient's anemia.
  • Genetic disorders affecting iron metabolism: These are rare and would be considered if other causes are ruled out and there's a family history or other suggestive findings.