Amplification of a gDNA by PCR using a forward primer in intron 3 and reverse primer in exon 4. (A) A heterozygous point mutation (G>T) was noted in the patient. The tracing shows the reverse strand. (B) Mutational analysis showing a mutation in the splice acceptor site of exon 4 leading to the use of an enforced cryptic splice acceptor site in exon 4 and a frameshift with premature termination in the Runt domain. WT indicates wild type.