The pediatric immune deficiency X-linked proliferative disease-2 (XLP-2) is a unique disease, with patients presenting with either hemophagocytic lymphohistiocytosis (HLH) or intestinal bowel disease (IBD).
This study aimed to investigate the frequencies and distributions of inherited variants in PRF1, UNC13D, STX11, STXBP2, SH2D1A, and XIAP genes in Chinese patients with HLH.
X-linked inhibitor of apoptosis protein (XIAP) deficiency is a rare immunodeficiency that is characterized by recurrent hemophagocytic lymphohistiocytosis (HLH) and splenomegaly and sometimes associated with refractory inflammatory bowel disease (IBD).
The X-linked inhibitor of apoptosis (XIAP) deficiency is a primary immunodeficiency characterized by Epstein-Barr virus (EBV)-driven hemophagocytic lymphohistiocytosis (HLH), splenomegaly, and colitis.
Haemophagocytic lymphohistiocytosis (HLH) is a life-threatening disorder of immune regulation, and HLH patients with mutations in genes including PRF1, UNC13D, STX11, STXBP2, SH2D1A, XIAP, and ITK were reported to be primary HLH.
The main clinical features of XLP-2 are (i) elevated susceptibility to hemophagocytic lymphohistiocytosis (HLH, frequently in response to infection with Epstein-Barr virus (EBV)), (ii) recurrent splenomegaly and (iii) inflammatory bowel disease (IBD) with the characteristics of Crohn's disease.
Based on this finding, an allogeneic hematopoietic progenitor cell transplant was performed to prevent the development of life-threatening hemophagocytic lymphohistiocytosis, in concordance with the recommended treatment for X-linked inhibitor of apoptosis deficiency.
Recurrent splenomegaly often associated with cytopenia and fever was preferentially observed in XLP-2 (XLP-1, 7%; XLP-2, 87%) and probably represents minimal forms of HLH as documented by histopathology.
Deficiency of X-linked inhibitor of apoptosis (XIAP), caused by BIRC4 gene mutations, is the second known cause of X-linked lymphoproliferative disease (XLP), a rare primary immunodeficiency that often presents with life-threatening hemophagocytic lymphohistiocytosis (HLH).
This heterozygous RAB27A mutation blurs the genetic distinction between primary and secondary HLH by contributing to HLH via a partial dominant-negative effect.
In a cohort of HLH patients with genetic abnormalities expected to result in the complete absence of perforin, Rab27a, or syntaxin-11, we found that disease severity as determined by age at HLH onset differed significantly, with a severity gradient from perforin (early onset) > Rab27a > syntaxin-11 (late onset).
Rab27a mutations cause type 2 Griscelli syndrome, which is characterized by immunodeficiency, including uncontrolled macrophage activation known as hemophagocytic syndrome.
Griscelli syndrome type 2 (GS2) is a rare autosomal-recessive disorder associated with a RAB27A gene mutation, and clinically manifesting as hypopigmentation, disseminated chronic encephalitis, and severe immunological disorders characterized by an accelerated hematological phase, also referred to as hemophagocytic syndrome (HS), or hemophagocytic lymphohistiocytosis (HLH).