Idelalisib is an oral, phosphatidylinositol 3-kinase delta (PI3Kδ) inhibitor, approved by FDA since July 2014 for the treatment of relapsed follicular B-cell non-Hodgkin lymphoma. Data from three phases of the study involving idelalisib demonstrate diarrhea (47%) to be the common adverse effect. The other side effects are pyrexia (28%), fatigue (30%), nausea (29%), cough (29%), pneumonia (25%), abdominal pain (26%) and rash (21%). The characteristic histological findings of idelalisib colitis include intraepithelial lymphocytosis, neutrophilic cryptitis and epithelial cell apoptosis within the crypts. Histological findings help differentiate among other causes of diarrhea and entero-colitis. We present a female patient with recurrent follicular lymphoma treated with idelalisib and presented with diarrhea. She was found to have entero-colitis and was treated successfully with drug discontinuation and prednisone.

Phosphatidylinositol 3-kinase δ (PIK3δ) is a tyrosine kinase essential for B cell survival, making it an important target in the treatment of chronic lymphocytic leukemia. Idelalisib is an inhibitor of PIK3δ demonstrating initial success in disease response, but is now shown to have a decreased overall survival and life-threatening serious adverse events. The following is an unfortunate case of a grade III adverse skin reaction secondary to idelalisib with the likely complication of methicillin-resistant Staphylococcus aureus bacteremia.

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