The challenge of early diagnosis of autoimmune lymphoproliferative syndrome in children with suspected autoinflammatory/autoimmune disorders.

Objectives: To test the usefulness of an extended panel of lymphocyte subsets in combination with Oliveira's diagnostic criteria for the identification of autoimmune lymphoproliferative syndrome (ALPS) in children referred to a paediatric rheumatology centre.
Methods: Patients referred from 2015 to 2018 to our rheumatology unit for an autoimmune or autoinflammatory condition were retrospectively analysed. Oliveira's required criteria [chronic lymphoproliferation and elevated double-negative T (DNT)] were applied as first screening. Flow cytometry study included double-negative CD4-CD8-TCRαβ+ T lymphocytes (DNT), CD25+CD3+, HLA-DR+CD3+ T cells, B220+ T cells and CD27+ B cells. Data were analysed with a univariate logistic regression analysis, followed by a multivariate analysis. Sensitivity and specificity of the Oliveira's required criteria were calculated.
Results: A total of 264 patients were included in the study and classified as: (i) autoimmune diseases (n = 26); (ii) juvenile idiopathic arthritis (JIA) (35); (iii) monogenic systemic autoinflammatory disease (27); (iv) periodic fever, aphthous stomatitis, pharyngitis and adenitis syndrome (100); (v) systemic undefined recurrent fever (45); (vi) undetermined-systemic autoinflammatory disease (14); or (vii) ALPS (17). Oliveira's required criteria displayed a sensitivity of 100% and specificity of 79%. When compared with other diseases the TCRαβ+B220+ lymphocytes were significantly increased in ALPS patients. The multivariate analysis revealed five clinical/laboratory parameters positively associated to ALPS: splenomegaly, female gender, arthralgia, elevated DNT and TCRαβ+B220+ lymphocytes.
Conclusions: Oliveira's required criteria are useful for the early suspicion of ALPS. TCRαβ+B220+ lymphocytes should be added in the diagnostic work-up of patients referred to the paediatric rheumatology unit for a suspected autoimmune or autoinflammatory condition, providing a relevant support in the early diagnosis of ALPS.
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