The ATP‐dependent DNA helicase Q4 (RECQL4) belongs to a family of conserved RECQ helicases that are felt to be important in maintaining chromosomal integrity (Kitao et al.,1998, Genomics: 54 (3): 443–452; (6)). Deletions in the RECQL4 gene located on chromosome 8 region q24.3 have been associated with Rothmund–Thomson syndrome (RTS, OMIM 268400), a condition characterized by poikiloderma, sparse hair, small stature, skeletal abnormalities, cataracts and an increased risk of malignancy (1–2, 5). We present a patient with a molecularly confirmed diagnosis of RTS with two unique genetic alterations in RECQL4 (IVS16‐2A>T and IVS2+27_51del25), who at the age of 7 months nearly succumbed to Pneumocystis carinii pneumonia. Evaluation of his immune system demonstrated a T^–B⁺NK^– phenotype with agammaglobulinemia consistent with combined immunodeficiency (CID). Studies to evaluate for known genetic causes of CID were not revealing. The patient received an umbilical cord blood (UCB) transplant with complete immune reconstitution. This report represents the first description of a CID phenotype and UCB transplantation in a patient with RTS.