Abstract
Severe combined immunodeficiency (SCID) is the most severe form of primary immunodeficiency. The hematopoietic stem cell transplantation is essential for the most types of SCID to survive. Early diagnosis and prevention of infection is important. We report a case of SCID and Pneumocystis jirovecii pneumonia, which occurred in a 4-month-old girl. She presented with slowly progressive respiratory failure and failure to thrive without an episode of fever. On admission, her SpO2 was 85% (room air). Her WBC count was normal with low lymphocyte count, and her CRP value was normal. A chest X-ray revealed bilateral infiltrates and absence of thymus. In spite of standard antibiotic treatment, her respiratory condition exacerbated. Considering her atypical clinical course, we checked her immunological status and detected absence of T cell and B cell function. She was diagnosed as having SCID, and Pneumocystis jirovecii was detected in her sputum by PCR (polymerase chain reaction). Trimethoprim-sulfamethoxazole was started and her respiratory status improved, after which HLA (human leukocyte antigen)-matched umbilical cord blood hematopoietic stem cell transplantation was successfully done. When we take care of an infant with severe infection with atypical clinical course such as not-responding to standard antibiotic therapy, the possibility of primary immunodeficiency should be considered.
