STX11 mutations and clinical phenotypes of familial hemophagocytic lymphohistiocytosis in North America.
BACKGROUND
Mutations in STX11 are responsible for Familial Hemophagocytic Lymphohistiocytosis (FHLH) type 4, a rare primary immunodeficiency which has previously been observed only in patients of Kurdish, Turkish, and Lebanese ethnic background.


METHODS
We reviewed our experience with STX11 mutations among North American patients and studied the impact of patient mutations upon syntaxin 11 expression and NK cell function.


RESULTS
Between 2007 and 2008, 243 patients with HLH (lacking disease-causing mutations in PRF1 and UNC13D) were referred for STX11 mutational analysis. We observed 1 novel homozygous nonsense mutation, 73 G > T (E25X), occurring in Hispanic siblings, and 2 novel biallelic heterozygous missense mutations, 106G > C (E36Q) and 616G > A (E206K), occurring in 1 Caucasian patient. The N-terminal nonsense mutation resulted in absence of detectable syntaxin 11 and abrogation of in vitro NK cell degranulation and function, while the biallelic heterozygous missense mutations resulted in detectable mutated syntaxin 11 and preservation of in vitro NK cell degranulation and cytotoxicity. The two sibling patients with the nonsense mutations presented with HLH during infancy, whereas the patient with biallelic heterozygous missense mutations presented at 5 years of age.


CONCLUSIONS
We conclude that mutations in STX11 are responsible for HLH in approximately 1% of North American patients and can cause variable defects in syntaxin 11 expression and function with resultant impact on clinical phenotype.
Marsh
Rebecca A
RA
Division of Bone Marrow Transplant and Immune Deficiency, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio 45229, USA. rebecca.marsh@cchmc.org
Satake
Noriko
N
Biroschak
Jennifer
J
Jacobs
Thedia
T
Johnson
Judith
J
Jordan
Michael B
MB
Bleesing
Jack J
JJ
Filipovich
Alexandra H
AH
Zhang
Kejian
K
D000328:Adult; D002675:Child, Preschool; D004252:DNA Mutational Analysis; D004273:DNA, Neoplasm / Q000235:genetics; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D007694:Killer Cells, Natural / Q000187:drug effects / Q000378:metabolism; D051359:Lymphohistiocytosis, Hemophagocytic / Q000175:diagnosis / Q000188:drug therapy / Q000235:genetics*; D008297:Male; D009154:Mutation; D009656:North America; D010375:Pedigree; D010641:Phenotype; D050765:Qa-SNARE Proteins / Q000235:genetics*; D035781:Siblings
D004273:DNA, Neoplasm; D050765:Qa-SNARE Proteins; C541732:STX11 protein, human