Acquired Immunodeficiency in Newborn Following Intrauterine Exposure to Thiopurines for Treatment of Inflammatory Bowel Disease

Thiopurine-based therapy is a common immunosuppressive treatment of inflammatory bowel diseases. It inhibits purine synthesis, and its metabolism is influenced by genetic variation. Thiopurines, azathioprine and 6-mercaptopurine (6-MP), have not been identified as teratogenic in humans and are considered safe to use during pregnancy. Here, we present 3 infants who developed severe lymphopenia secondary to prenatal exposure. Clinicians should be aware of this uncommon but potentially severe side effects.