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case_images: NK cell degranulation assay. PBMCs were isolated and co-incubated with a specific proportion of K562 cells for stimulation or incubated with medium alone (control group). Flow cytometry was then performed with anti-CD3 (FITC), anti-CD56 (APC) and anti-CD107a-PE labeled samples. CD3-CD56+NK cells were gated to assess their expression in response to K562 stimulation and non-stimulation by measuring amplitude changes in CD107a (NK-DeltaCD107a) surface expression. The reference intervals were defined as <5% being deficient, >5% and <10% being abnormal, and >10% being normal.
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case_images: With recurrent fever (temperature >=38.5 C for over 7 days), leukopenia, decreased hemoglobin, elevated triglycerides, decreased fibrinogen, elevated ferritin, decreased NK cell count, and reduced NK cell activity, along with increased soluble CD25 levels, and NK cell CD107a degranulation assay suggesting impaired NK cell function (Figure 1), a diagnosis of HLH was considered.
case_images: Bone marrow examination: active bone marrow hyperplasia, normal granulocyte lines with reactivity changes, elevated red blood cell lines, normal megakaryocyte lines, and observed tissue hemophagocytosis. (A) Bone marrow pathology (HE staining, x80): bone marrow cells phagocytosis of nucleated red cells (as shown by arrow). (B) Bone marrow cytology (Reye's staining, x100 oil mirror): bone marrow cells phagocytosis of granulocytes and nucleated red cells.
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case_images: The examination revealed the tissue hemophagocytosis (Figure 2).
case_images: Exome sequencing revealed heterozygous mutations in UNC13D gene.
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case_images: Exome sequencing showed NM_199242.3 (UNC13D): c.1280G >A p.(Arg427Gln), suggesting heterozygous variation in UNC13D gene (Figure 3).