[Clinical and immunological analysis of the patient with autoimmunity due to germline STAT3 gain-of-function...

Objective: To investigate the clinical and immunological laboratory features and gene mutation in a female patient who carried a germline gain-of-function mutation in STAT3. Method: A patient with lymphadenopathy and pancytopenia, visited the Department of Rheumatology and Immunology of Children's Hospital of Chongqing Medical University in May 2016. The clinical and laboratory characteristics, results of immunophenotyping and exome sequencing were analyzed retrospectively and related literature was reviewed. Result: The patient was a four years old girl. The clinical manifestation consisted of autoimmune pancytopenia, lymphadenopathy and recurrent infections. Multiple exams showed that peripheral blood leukocyte count was (2.2-4.9)×10⁹/L, red blood cell count was (2.09-5.75)×10⁹/L, hemoglobin level was 64-165 g/L, platelet count was (52-138) ×10⁹/L. Percentages of lymphocyte subsets showed that CD3⁺ T lymphocyte was 0.716 0 (CD4⁺ T lymphocyte was 0.326 0, CD8⁺ T lymphocyte was 0.323 0 and CD4^- CD8^-T TCRαβ⁺ lymphocyte was 0.029 0), CD19⁺ B lymphocyte was 0.235 0 (transitional B was 0.004 3), NK was 0.032 0. Percentages of CD4⁺ T lymphocyte release IL-4, IFN-γ, IL-17 and IL-21 were 0.014 9, 0.213, 0.024 0 and 0.021 0, respectively. Lymphocyte proliferation function and TCRVβ diversity were normal. The serum immunoglobulin levels were 16.4 g/L (IgG), 1.53 g/L (IgA), 3.99 g/L (IgM) and 3.20 kU/L (IgE). The patient carried a missense variant in the 21^st exon of STAT3, c. 1974G>C, p.K658N, which was previously described as a gain-of-function mutation. The patient was treated with methylprednisolone and prednisone intermittently. There were significant improvements of hepatosplenomegaly, lymphadenopathy and pancytopenia. We searched internal database and literature for cases with gain-of-function mutations in STAT3. A total of 19 cases were identified, all were non-Chinese. Among 16 cases who had clinical data, age of onset of 11 patients was less than 5 years. 14 cases had autoimmune hemolytic anemia, autoimmune thrombocytopenia or autoimmune neutropenia. Twelve patients had lymphadenopathy while 11 had infections and 5 had endocrine abnormalities. Conclusion: The patient with Primary immunodeficiency disease (PID) due to gain-of-function mutation in STAT3 gene often has early-onset autoimmune disorders, lymphadenopathy and recurrent infections. Since the routine immunological examination may be normal or slightly abnormal, comprehensive evaluation of immune function should be done. Genetic testing ultimately helps to confirm the diagnosis.