A 278bp deletion occurs which starts in intron "A" and includes exon "B" and the first 78bp of exon "C". As a result of this deletion, mRNA transcription is reduced to about 35% of normal and includes two forms, a longer normal length transcript and a shorter misspliced form. If these mRNAs were translated they both would result in truncated products. Protein product is undetectable immunologically and there is a total absence of enzyme activity. (J:12776, J:50729)