Roseomonas bacteremia: A clue to underlying severe combined immunodeficiency.

Abstract

Background:
Severe combined immunodeficiency (SCID) is a rare but fatal inborn error of immunity characterized by profound defects in cellular and humoral immunity. It predisposes infants to severe, recurrent opportunistic infections. Unusual or low-virulence pathogens may serve as early clinical clues to an underlying immunodeficiency. Roseomonas species are slow-growing, gram-negative bacilli with low pathogenic potential and are rarely implicated in paediatric infections and predominantly affect immunocompromised hosts.

Case Report:
A 40-day-old male infant with an unremarkable perinatal history presented with high-grade fever and elevated inflammatory markers. Evaluation showed leukocytosis, raised C-reactive protein and multiple hepatic microabscesses on ultrasonography.  Cerebrospinal fluid analysis was unremarkable. During hospitalisation, he developed multiple pustular skin lesions and blood culture grew a slow-growing Roseomonas species identified by the VITEK system. Antibiotics were adjusted according to susceptibility which led to clinical improvement and resolution of hepatic abscesses. Owing to the unusual organism and hepatic abscesses, an inborn error of immunity was suspected. At nine months of age, the child was hospitalised again with recurrent lower respiratory tract infections, pneumonia, mucocutaneous candidiasis and failure to thrive. Immunological workup revealed markedly reduced CD3 and CD56 cells with hypogammaglobulinemia, absence of the thymic shadow on chest radiography. Genetic studies confirmed X-linked SCID due to a hemizygous stop-gain mutation in IL2RG gene. He was referred for hematopoietic stem cell transplantation.

Conclusion:
Paediatricians should maintain a high index of suspicion for inborn errors of immunity in infants presenting with unusual or opportunistic infections including Roseomonas infection. This will enable early diagnosis and appropriate interventions at an early and appropriate time.