Retrospective review of serum immunoglobulin levels in 78 methotrexate treated paediatric rheumatology patients showed that IgG, IgA, and IgM levels fell significantly by 26%, 21%, and 17% respectively while on methotrexate. Six patients with systemic disease showed a fall in IgG to below the normal range.
The effects of methotrexate on serum immunoglobulin (Ig) concentrations in paediatric rheumatology patients have not previously been studied. In our unit it has been noted anecdotally that Ig levels can fall in these patients, sometimes to below the normal range. If this is confirmed it may have implications on what we must tell patientsand their families regarding methotrexate and immunosuppression.
This study was carried out to determine the effect of methotrexate on serum immunoglobulin concentrations in paediatric rheumatology patients.
This was essentially a retrospective case note review. All the patients under the care of the paediatric rheumatologists at Alder Hey Children's Hospital who are being or have been treated with methotrexate in the past two years were included. They were identified from the consultants' and rheumatology research nurses' lists and from pharmacy records, yielding 78 names. Fifty two had polyarticular juvenile idiopathic arthritis (JIA), 17 had systemic onset JIA, and nine had other connective tissue diseases. Fifty two were on standard low dose methotrexate (10 mg/[m.sup.2]). and 26 on medium dose (15-20 mg/[m.sup.2]).
The case notes were examined and immunoglobulin concentrations pretreatment and more than three months after treatment with methotrexate was commenced were obtained. Where possible results were sought from other hospitals where these patients are seen jointly as shared care. Results were also obtained prospectively when patients were having their routine blood monitoring. No extra blood sampling was done.
The concentrations of IgG, IgA, and IgM were compared pre- and post-treatment. Where there was a fall in IgG to below the normal range, IgG subclasses were also measured. The results were analysed using a two tailed t test.