Differential Diagnosis for Diarrhea and Scleritis

The patient presents with a combination of watery stools and scleritis, which is inflammation of the sclera, the white part of the eye. This combination of symptoms can be associated with various conditions, ranging from infectious to autoimmune diseases. Here's a categorized differential diagnosis:

• Single Most Likely Diagnosis

  • Inflammatory Bowel Disease (IBD): Conditions like Crohn's disease and ulcerative colitis can cause chronic diarrhea and are associated with extraintestinal manifestations, including eye inflammation like scleritis. The absence of abdominal pain does not rule out IBD, as some patients may present with minimal gastrointestinal symptoms.

• Other Likely Diagnoses

  • Infectious Gastroenteritis: Certain infections can cause prolonged diarrhea and, in rare cases, may be associated with systemic symptoms including eye inflammation.
  • IgA Nephropathy (Berger's disease): This condition can present with gastrointestinal symptoms and eye involvement, including scleritis, though it's more commonly associated with nephritic syndrome.
  • Reactive Arthritis: Previously known as Reiter's syndrome, this form of arthritis can occur after certain bacterial infections and is characterized by the triad of arthritis, urethritis, and conjunctivitis, but can also include diarrhea and scleritis in some cases.

• Do Not Miss Diagnoses

  • Wegener's Granulomatosis (Granulomatosis with Polyangiitis): A systemic vasculitis that can affect multiple organs, including the eyes (causing scleritis) and gastrointestinal tract (causing diarrhea), and is potentially life-threatening if not treated promptly.
  • Systemic Lupus Erythematosus (SLE): An autoimmune disease that can affect virtually any organ system, including causing gastrointestinal symptoms and eye inflammation like scleritis. Missing this diagnosis could lead to significant morbidity.

• Rare Diagnoses

  • Whipple's Disease: A rare, systemic bacterial infection that can cause diarrhea, weight loss, and arthralgias, and in some cases, eye inflammation.
  • Sarcoidosis: An autoimmune disease that can affect multiple organs, including the lungs, skin, and eyes. Gastrointestinal symptoms are less common but can occur, and eye involvement, including scleritis, is a known manifestation.
  • Behçet's Disease: A form of vasculitis that can cause a wide range of symptoms, including oral and genital ulcers, skin lesions, and eye inflammation. Gastrointestinal involvement, including diarrhea, can occur but is less common.

Each of these diagnoses has a different level of likelihood based on the patient's presentation, but considering the combination of diarrhea and scleritis, it's crucial to evaluate for both common and rare conditions to ensure proper diagnosis and treatment.