Clostridioides difficile (C. difficile) infection: This is the most common cause of pseudomembranous colitis, especially in patients who have recently used antibiotics, have been hospitalized, or have a compromised immune system. C. difficile infection is known for producing toxins that cause the characteristic pseudomembranes and colitis.

Staphylococcal enterocolitis: Caused by Staphylococcus aureus, this condition can also lead to pseudomembranous colitis, though it is less common than C. difficile. It often occurs in the setting of antibiotic use.
Ischemic colitis: While not typically pseudomembranous, ischemic colitis can present with similar symptoms such as abdominal pain and diarrhea. It is caused by reduced blood flow to the colon.
Inflammatory bowel disease (IBD): Conditions like Crohn's disease and ulcerative colitis can cause colitis and sometimes may be confused with pseudomembranous colitis, especially if there is a significant inflammatory component.

Neutropenic colitis (typhlitis): This condition occurs in neutropenic patients and can rapidly progress to perforation and sepsis if not promptly treated. It's crucial to consider in immunocompromised patients.
CMV colitis: Cytomegalovirus (CMV) can cause colitis in immunocompromised individuals, including those with HIV/AIDS or transplant recipients. It can present similarly to pseudomembranous colitis and requires specific antiviral treatment.

Pseudomembranous colitis due to other bacterial infections: Rarely, other bacteria such as Klebsiella oxytoca can cause pseudomembranous colitis.
Fungal infections: Certain fungal infections, though exceedingly rare, can mimic pseudomembranous colitis in severely immunocompromised patients.
Chemical colitis: Caused by the ingestion of caustic substances, this can lead to colonic inflammation and potentially mimic pseudomembranous colitis in its presentation.