Background Fever of unknown (FUO) origin often presents a unique diagnostic challenge to the paediatrician. We present a unique case of a 4 month old boy with fever for 1 month, who after extensive work up was diagnosed with pulmonary tuberculosis and Severe Combined Immunodeficiency (SCID).

Case Report Our case is a 4 month old, Sudanese boy, residing in Qatar, who presented to our hospital with fever for two weeks. He remained febrile in the hospital for two weeks, despite receiving Intravenous antibiotics for presumed partially treated meningitis. He also received IVIG for the suspicion of atypical Kawasaki. Computerised tomography of the head and abdomen and bone marrow studies were also inconclusive. The mother subsequently revealed that a previous child had died during infancy with prolonged fever and no specific diagnosis. This alerted the treating physicians to the possibility of immunodeficiency. Our patient had received BCG vaccine at birth without any complications, and three gastric aspirate samples were negative for tuberculosis. A broncho-alveolar lavage was performed, despite the absence of any respiratory symptoms, to exclude any unusual organisms causing prolonged fever. The broncho-alveolar lavage revealed mycobacterium tuberculosis which was resistant to Isoniazid and the patient was started on appropriate anti-Tuberculous medications. The total immunoglobulin counts and Flow cytometry were suggestive of SCID.

Conclusion Pulmonary Tuberculosis should be considered as a differential diagnosis of FUO, especially in infants with suspected or proven SCID. Attaining a good family history is crucial in early diagnosis of SCID and hence possibly in saving lives.