Differential Diagnosis for a 30-year-old Woman with Diarrhea and Abdominal Pain

The patient's presentation of diarrhea, abdominal pain, fatigue, weight loss, and a history of arthritis and erythema nodosum suggests an inflammatory bowel disease. Here is the differential diagnosis, categorized for clarity:

• Single most likely diagnosis

  • B. Crohn’s disease: This is the most likely diagnosis given the patient's symptoms of chronic diarrhea, abdominal pain, fatigue, weight loss, and a history of arthritis and erythema nodosum, which are extraintestinal manifestations commonly associated with Crohn's disease.

• Other Likely diagnoses

  • C. Irritable bowel syndrome (IBS): Although IBS could explain the change in bowel movements and abdominal pain, the presence of weight loss, fatigue, and extraintestinal manifestations makes it less likely than Crohn's disease.
  • D. Diverticulitis: This condition could cause abdominal pain and tenderness, especially in the lower left quadrant, but it typically presents with more acute symptoms and fever, which are not prominent in this case.

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

  • A. Bowel obstruction: Although the patient's symptoms do not strongly suggest a bowel obstruction (e.g., no mention of obstipation, severe abdominal distension, or high-pitched bowel sounds), this condition is a medical emergency that requires prompt diagnosis and treatment. The presence of abdominal pain and tenderness warrants consideration of this diagnosis.
  • Infectious colitis: This could present with similar symptoms, including diarrhea and abdominal pain, and is important to rule out due to the potential for severe complications if not treated appropriately.

• Rare diagnoses

  • Microscopic colitis: This condition can cause chronic diarrhea but typically does not cause abdominal pain or weight loss to the extent described in this patient.
  • Celiac disease: Although celiac disease can cause diarrhea, abdominal pain, and weight loss, the presence of extraintestinal manifestations like arthritis and erythema nodosum, along with the specific gastrointestinal symptoms, makes Crohn's disease more likely in this case.
  • Other inflammatory or infectious causes: There are numerous other rare conditions that could potentially explain this patient's symptoms, including other types of inflammatory bowel disease, eosinophilic gastroenteritis, or parasitic infections, among others. A thorough diagnostic workup would be necessary to consider these possibilities.