[Two cases of deficiency in ELF4 gene X-linked and literature review].

To summarize the clinical phenotype and genetic characteristics of deficiency in ELF4 gene X-linked (DEX). A case series study was conducted to retrospectively analyze the clinical data and genetic testing results of 2 cases of DEX treated at Peking Union Medical College Hospital, Chinese Academy of Medical Sciences and the First Hospital of Jilin University from January 2023 to April 2024. And literature up to April 2024 was searched from the PubMed database, as well as CNKI and Wanfang databases, using keywords such as "ELF4 deficiency" "deficiency in ELF4, X-linked""ELF4 gene". The main clinical manifestations and genotypes of DEX were summarized. Both patients were male, with onset ages of 3 months and 3 years, respectively. Both patients presented with recurrent oral ulcers and abdominal pain. And the laboratory examination showed a significant increase in inflammatory markers. Intestinal examinations showed multiple intestinal ulcers, and both patients developed intestinal fistulas. Whole exome sequencing found ELF4 c.799C>T, p Arg267Trp and ELF4 c. 248-7G>A, both maternal variants. Based on clinical and genetic results, DEX were diagnosed. In terms of treatment, both patients underwent surgical treatment during the acute phase of the disease and received anti-tumor necrosis factor α therapy, but recurrent gastrointestinal symptoms were still observed in Patient 1, while the clinical effect in Patient 2 was still acceptable. However, the inflammatory markers in both patients were not normal even after treatment. Literature review found 18 patients including 2 patients in this study, reported in 5 English articles and no Chinese reports. Thirteen patients had disease onset age before 5. The main clinical manifestations were fever (12/17), oral ulcers (14/18), abdominal pain (8/18), diarrhea (6/18), perianal ulcers (5/17), ileum ulcers (6/16), colon ulcers (7/16), skin involvement (7/17) and recurrent infections (7/18); laboratory examinations found increased erythrocyte sedimentation rate (13/15) as well as C-reactive protein (9/9), and anemia (13/15); in terms of immunological function, there is a decrease in natural killer cells (9/15) as well as a decrease in class switching memory B cells (8/9). The main types of gene variantions were missense variantions (6/18), nonsense variantions (4/18) or frameshift variantions (3/18). DEX should be considered when an early-onset male patient manifested with recurrent fever, oral ulcers or mucosal ulcers, with elevated inflammatory markers, with or without recurrent infection. It is recommended to perform lymphocyte subsets analysis, gastrointestinal endoscopy and genetic testing to support the diagnosis.