Table 1.

Summary of eight studies examining the percentage of patients with different forms of familial haemophagocytic lymphohistiocytosis (FHL). Column 1 provides the references, column 2 summarizes the patients and their ethnic origin and column 3 provides percentages for the different types of FHL. Seven of the studies used genetic analysis and one protein screening.

Reference	Numerical breakdown	Percentages
‘Spectrum of perforin gene mutations in familial hemophagocytic lymphohistiocytosis’[28]	34 families from various countries 7 families FHL2 mutations	FHL1 = 10% FHL2 = 20% (FHL2 = 30% in Turkish patients) FHL2 = 20–40% (mutations and polymorphism)
‘Characterisation of diverse PRF1 mutations leading to decreased NK cell activity in North American families with haemophagocytic lymphohistiocytosis’[31]	50 families from North America 43 studied for perforin mutations (the other 7 unlikely to be FHL2) 25 families FHL2	FHL2 = 50%
‘Genetic subtypes of familial hemophagocytic lymphohistiocytosis: correlations with clinical features and cytotoxic T lymphocyte/natural killer cell functions’[39]	35 patients with FHL in Japan 11 patients FHL2 8 patients FHL3 16 patients non-FHL2/FH3	FHL2 = 31% FHL3 = 23% Non-FHL2/3 = 46%
‘Spectrum and clinical implications of syntaxin 11 gene mutations in FHL: association with disease-free remissions and haematopoietic malignancies’[43]	28 families non-FHL2, various countries of origin 4 families FHL4 (all Turkish)	FHL4 = 14% of non-FHL2
‘Novel Munc13–4 mutations in children and young adults with haemophagocytic lymphohistiocytosis’[38]	30 families with FHL, non- FHL2 (26 of Italian origin) 15 families FHL3	FHL3 = 50% of non-FHL2 cases
‘Mutation spectrum in children with primary hemophagocytic lymphohistiocytosis: molecular and functional analysis of PRF1, UNC13D, STX11 and RAB27A’[35]	63 unrelated patients from various ethnic backgrounds 38 patients with mutations 20 patients FHL1 12 patients FHL2 6 patients FHL4 (all Turkish)	FHL2 = 32% FHL3 = 19% FHL4 = 9·5% Gene defect found; 80% of Turkish and 30% of German patients
‘Familial hemophagocytic lymphohistiocytosis: protein screening, genetic analysis and ethnicity’ Walshe D, Peraj R, Maeney C XIIth Meeting of the ESID, 2006	88 FHL patients from various ethnic backgrounds underwent protein screening	Perforin = 19% Munc13–4 = 25% SAP = 4% 52% cause not identified
‘Munc18-2 deficiency causes familial hemophagocytic lymphohistiocytosis type 5 and impairs cytotoxic granule exocytosis in patient NK cells’[45]	80 FHL patients, ethnic background not reported	FHL2 + FHL3 + FHL4 = 80% FHL5 = 10% Unknown = 10%