Linkage analysis of index family, STK4 mutation, and absence of STK4 protein expression in the patients. (A) Pedigree of the family with SNP and microsatellite markers on chromosome 20. Gray shading represents the homozygous interval. Nomenclature of the persons in the text is as follows: II-1 indicates HET2; II-2, HET1; II-4, P1; II-5, P2; and III-1, P3. (B) Sanger sequencing of STK4 shows a nucleotide substitution G/A in exon 7, which leads to premature stop codon mutation. (C) Detection of STK4 protein in PBMCs by Western blot. All 3 STK4-deficient patients do not show any protein expression.