Identification of biallelic perforin mutations inherited by a female patient presenting with HLH. (A) Family tree indicating the perforin phenotype in each member of the patient's family. (B) Comparison of the perforin gene sequence of the patient and a normal WT control. One mutation was G145 > A, mapping to exon 2, and resulting in the substitution of aspartate 49 by asparagine (D49N), whereas the other was a deletion of nucleotides 853 to 855 in exon 3, resulting in the in-frame deletion of lysine 285 (K285del).