This case report describes a 14-year-old boy who presented to the emergency department with symptoms of severe anemia. He was diagnosed with autoimmune hemolytic anemia, and on further investigation, it was noted that he had no functioning T cells. Despite no antecedent history of severe infection, he was worked up for a severe combined immunodeficiency, and was found to have a compound hypomorphic mutation in an enzyme responsible for recombination of the B- and T-cell receptors. He was subsequently diagnosed with severe combined immunodeficiency, presenting with autoimmunity, and received a bone marrow transplant. As our knowledge of the immune system continues to expand, we are learning that dysregulation can occur in any one of the complex immune pathways, and may have a variety of clinical presentations. A high index of suspicion for immune defects should be maintained in cases of atypical or severe infections, autoimmunity or malignancy, particularly by the general practitioner, who is often the first to encounter these challenging patients.