Summary
A case of very severe P. T. A. deficiency without hemorrhagic symptoms is described,
and the possibility that the absence of a bleeding diathesis may have an explanation
in the presently unknown interrelationship between 3 “contact phase” coagulation factors
is suggested. The existence of “Fletcher factor” deficiency as an entity distinct
from factor XI and XII deficiency is confirmed. The problems in establishing a diagnosis
of P. T. A. deficiency are discussed. The authors believe that assay using known congenitally
deficient plasma is the only certain method of diagnosing P. T. A. deficiency. The
3 members of the propositus’s family have minor P. T. A. deficiency, and the mode
of inheritance in this family is consistent with the hypothesis of Rapaport et al.
