Ten patients were severely affected with symptoms before the age of one year (P1, P2, P7, P15, P16, P23, P26, P30, P44, and P46): all but P23 had a combined deficiency of FII, FVII, FIX and FX; for P46 the FIX function was not determined; and none of the severely affected patients had cutis laxa or other PXE-like skin or eye manifestations. The gene discussed is F9; the disease is Pseudoxanthoma elasticum.