Homozygous protein S deficiency due to a one base pair deletion that leads to a stop codon in exon III of the protein S gene.

Homozygous protein S (PS) deficiency is a very rare disorder that causes purpura fulminans in affected newborns. This report describes the molecular genetic abnormality of a severe PS deficient child who developed purpura fulminans shortly after birth. The mutation was identified as a deletion of one adenine in codon 43 of exon III of the PROS 1 gene. This mutation results in a frameshift and a novel stop codon at position 45. The proband was apparently homozygous and his mother heterozygous for this mutation. The proband's father was not available for study. The single base pair deletion predicts a truncated translation product, where Lys 43 and Tyr 44 have been replaced by Asn 43 and Thr 44. This putative protein (predicted mw of 5.696 daltons) contains only the gammacarboxyglutamic acid (Gla) domain and the aromatic stack.