The JAK2 V617F mutation is found in ~95% of cases with PV,
however approximately 5% of patients do not have this mutation.
It has been reported that the majority of the JAK2 V617F
negative PV patients have a mutation in an alternative region of
the JAK2 gene, within exon 12.
Currently we are able to send an appropriate aliquot of the
archived DNA sample for screening exon 12 to our collaborators, on
behalf of referrers.