High prevalence of primary immune deficiencies in children with autoimmune disorders.

Objectives: Autoimmunity is a well-recognised manifestation of primary immunodeficiency disorders. However, the prevalence of primary immunodeficiency among children with autoimmune diseases is not well characterised. The objective of this retrospective study was to describe the prevalence of primary immunodeficiency disorders in a paediatric population with autoimmune diseases.

Methods: We retrospectively analysed a cohort of patients investigated for diverse autoimmune conditions from June 1st 2005 to December 31st 2006 in the Rheumatology and Immunology service of a tertiary care paediatric hospital in Canada. The clinical data of patients were reported. Independently of their baseline characteristics, patients underwent a systematic immunologic workup, which was performed before treatment initiation.

Results: Thirty-three patients were included in this study. We identified 5 patients (15%) with a primary immunodeficiency disorder: common variable immunodeficiency (n=2), combined immunodeficiency (n=1) and complement component deficiency (n=2). Four other patients (12%) displayed decreased levels of immunoglobulins, B-cell lymphopenia and/or abnormal vaccinal response but did not fulfil the criteria of a defined primary immunodeficiency disorder at the time of the study. Importantly, none of these 9 patients had a particular familial history and none had a history of recurrent infections.

Conclusions: A significant proportion of patients presenting with an autoimmune condition have an underlying primary immunodeficiency disorder that may not be clinically obvious. Additional prospective investigations are needed to further define the role for routine immunologic testing in daily clinical rheumatologic practice.