X-linked familial hemophagocytic lymphohistiocytosis; XIAP deficiency; X-linked lymphoproliferative syndrome type 2 (XLP-2)-MAS
Macrophage Activation Diseases
X-linked. X-linked dominant male inheritance (typical presentation). There are some female carriers with some symptoms. Testing recommended for XIAP (and also SAP) in males with symptoms of HLH after Epstein-Barr virus (EBV) infections, or HLH presenting in childhood or adolescence. 
Timing of symptoms:
Onset of HLH may be the first sign of this disease, and may occur after Epstein-Barr infections (that can be severe).  Some cases developed pancytopenia and splenomegaly after MMR vaccine. 
Higher risk for early-onset inflammatory bowel diseases (Crohns, colitis, IBD), even in female carriers of the XIAP deficiency mutation.  Hepatomegaly, splenomegaly, granulomatous hepatitis.   Chronic and/or hemorrhagic colitis that can be fatal (one case with portal hypertension).  Crohns-like disease, celiac-like disease.  Some patients with chronic liver failure and/or hepatitis.  Cholangitis (sometimes associated with colitis). 
Splenomegaly (may be the first presenting symptom).  Hemophagocytic lymphohistiocytosis (HLH) affects 90% of cases  and many can have recurrent HLH. HLH can occur after Epstein-Barr virus (EBV).   No known patients with lymphoma or aplastic anemia. 
One case with elevated serum amyloid.  Not tested in other cases in the literature.
High: ESR, CRP, liver function tests (LFTs), triglycerides, ferritin,  IL-18  cytopenia.  Low: fibrinogen, platelets, anemia, neutropenia, hemophagocytosis.  Normal NK cell function  Variable NKT cell defects.  IgG normal in untreated patients.  Low IgG secondary to treatments.  
X-linked familial hemophagocytic lymphohistiocytosis, XIAP deficiency, X-linked lymphoproliferative syndrome type 2 (XLP-2)-MAS, vaccine, vaccine triggered, MMR, Measles, XLP2-MAS, XLP-2, macrophage activation, macrophage activation syndrome, MAS, XIAP, BIRC4, lymphohistiocytosis, histiocytosis, hemophagocytic lymphohistiocytosis, HLH, X linked HLH, hemophagocytic lymphohistiocytosis epstein-barr virus, epstein-barr virus, pancytopenia, erythema nodosum, periodic fever, recurrent fever, fever, periodic fever HLH, viral triggered HLH, mono, mononulcleosis, mononulcleosis HLH, mononulcleosis hemophagocytic lymphohistiocytosis, uveitis, cataracts, inflammatory bowel diseases, early onset inflammatory bowel disease, abdominal pain, hepatomegaly, splenomegaly, granulomatous hepatitis, colitis, Crohns, IBD, hemorrhagic colitis, portal hypertension, cholangitis, hepatitis, arthritis, myositis, hepatosplenomegaly, enlarged liver, enlarged spleen, enlarged liver and spleen, large liver, large spleen, large liver and spleen, anemia, amyloid, triglycerides, ferritin, IL-18, cytopenia, high liver function tests, neutropenia, hemophagocytosis, joint pain, leg pain, liver failure, granulomatous hepatitis, granulomatous, Epstein-Barr, EBV, mono, mononucleosis
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