Differential Diagnosis for Exertional Fatigue and Exercise Intolerance in a 10-year-old Boy
- Single most likely diagnosis:
- Iron deficiency anemia: The patient's low hemoglobin level (9.4 g/dL), microcytic anemia (mean corpuscular volume of 74 µm3), and presence of occult blood in the stool suggest iron deficiency anemia. The lack of other symptoms such as abdominal pain or black and tarry stools, and unremarkable upper endoscopy and colonoscopy results, point towards a chronic, slow blood loss, likely due to a gastrointestinal source that is not visible or has resolved by the time of endoscopy, such as a bleeding Meckel's diverticulum or intestinal polyp, but given the age and presentation, iron deficiency anemia due to inadequate dietary intake or other non-gastrointestinal causes should also be considered.
- Other Likely diagnoses:
- Celiac disease: Although the patient does not have abdominal pain, celiac disease can present with iron deficiency anemia due to malabsorption. The lack of other gastrointestinal symptoms does not rule out this diagnosis, as it can be asymptomatic or present with non-classical symptoms.
- Inflammatory bowel disease (IBD): Despite the unremarkable endoscopy and colonoscopy, IBD (such as Crohn's disease or ulcerative colitis) can have a patchy distribution and may not always be detected on initial endoscopy. The presence of occult blood and iron deficiency anemia, along with exertional fatigue, makes this a consideration, although less likely given the normal appearance of the mucosa on endoscopy.
- Do Not Miss diagnoses:
- Bleeding disorder (e.g., von Willebrand disease): Although coagulation studies are within normal limits, some bleeding disorders may not be detected by standard coagulation tests. A bleeding disorder could explain the iron deficiency anemia and exertional fatigue due to anemia.
- Intestinal lymphoma or other malignancies: Although rare in children, these conditions can present with iron deficiency anemia and exertional fatigue. The absence of lymphadenopathy, abdominal masses, or other systemic symptoms does not rule out this possibility entirely.
- Rare diagnoses:
- Hereditary spherocytosis or other hemoglobinopathies: These conditions can cause anemia but typically have distinct features on the complete blood count (e.g., spherocytes in hereditary spherocytosis) and may not fit perfectly with the patient's presentation.
- Gastric antral vascular ectasia (GAVE) or other vascular anomalies: These are rare causes of gastrointestinal bleeding and iron deficiency anemia but are less likely given the patient's age and the unremarkable endoscopy results.