[LIG4 syndrome: a report of four cases and literature review].

Objective: To analyze clinical, immunological and genetic characteristics of 4 cases of LIG4 syndrome. Methods: We retrospectively analyzed the clinical data of 4 patients from 3 families with LIG4 syndrome who were admitted to Children's Hospital of the Capital Institute of Pediatrics from June 2017 to May 2018, and reviewed related articles, the clinical, immunological and genetic characteristics of LIG4 syndrome were summarized and analyzed. Results: Those 4 cases (P1 to P4), including 2 males and 2 females, had an average age of 1.5 years. All of them presented with special facial features, such as microcephaly, beak-like-nose, and receding forehead. Three of them presented with delayed physical development. P3 suffered from mental retardation and P4 had feeding difficulty. BCG scars were repeatedly ruptured in 3 cases, 4 cases had pneumonia, 1 case had EB virus infection, 2 cases had cytomegalovirus infection, 1 case had fungal infection, and 1 case had chronic diarrhea. Blood routine tests showed decreased neutrophil and lymphocyte counts. Immunoassay showed decreased absolute count of CD4(+)T lymphocyte and B lymphocyte, with normal CD8(+)T cells. P1, P2 presented with decreased immunoglobulin. All of those patients had LIG4 gene complex heterozygous mutations, of whom one had missense mutation had mild clinical phenotype and another three cases had frameshift mutation presented with severe clinical phenotype. One patient underwent hematopoietic stem cell transplantation, and has established normal immune function. He did not have recurrent infection during one year follow-up period. The other 3 patients had preventive anti-infection treatment and received regular human immunoglobulin infusion, but they still had recurrent infection. In literature review, 67 articles were retrieved, totally 37 case were reported, showing special faces and recurrent infection as characteristic presentation of this disease. Conclusions: The typical manifestations of LIG4 syndrome are microcephaly, special facial features and repeated infection. The average age at diagnosis of LIG4 syndrome was more than one year old. If a patient presented with microcephaly, BCG scar infection and leukopenia, LIG4 syndrome should be considered. Immunoglobulin is decreased at different degrees, and CD4(+) and CD19(+) lymphocyte counts always decrease, Naive T and B cells decrease more prominently, and CD8(+)T cells were normal in patients with typical LIG4 syndrome. It is effective to reconstruction of immune system with bone marrow transplantation in LIG4 syndrome patients.