Differential Diagnosis

The patient's presentation of constipation, occasional abdominal pain, and falling hemoglobin after starting dexamethasone can be approached by considering the following categories:

• Single Most Likely Diagnosis

  • Steroid-induced peptic ulcer disease: The initiation of dexamethasone, a corticosteroid, can lead to an increased risk of peptic ulcer disease, which may cause abdominal pain and gastrointestinal bleeding, resulting in a falling hemoglobin level. Constipation could be a side effect of the medication or unrelated.

• Other Likely Diagnoses

  • Inflammatory bowel disease (IBD) flare: Although dexamethasone is used to treat IBD, the patient's symptoms could indicate a flare of the disease, especially if the dose is not sufficient or if there's a complication like a stricture causing constipation.
  • Gastrointestinal malignancy: Abdominal pain, constipation (if due to obstruction), and anemia could be symptoms of a gastrointestinal cancer, though this would be less directly related to the initiation of dexamethasone.

• Do Not Miss Diagnoses

  • Gastrointestinal perforation: A serious and potentially life-threatening condition that could be caused by steroid-induced peptic ulcer disease or another process. Symptoms might include severe abdominal pain.
  • Bleeding disorder or thrombocytopenia: Though less common, these conditions could lead to bleeding and a drop in hemoglobin. The use of steroids might mask some symptoms or affect platelet count.
  • Diverticulitis or diverticular bleeding: Especially in older adults, diverticular disease could cause abdominal pain and bleeding, leading to anemia.

• Rare Diagnoses

  • Amyloidosis: A condition where abnormal proteins (amyloid) accumulate in organs, potentially causing constipation, abdominal pain, and anemia, though this would be an uncommon presentation.
  • Systemic mastocytosis: A rare condition where mast cells accumulate in various tissues, potentially causing gastrointestinal symptoms, including abdominal pain and changes in bowel habits, though anemia would be less directly related to dexamethasone use in this context.