IFNA1 and thanatophoric dysplasia: Seven of the 88 patients (8.0%) who had received regular IFN-α monotherapy developed TD, while 14 out of 163 patients (8.6%) who received regular IFN-α plus ribavirin combination therapy and 47 of 341 patients (13.8%) who received Peg-IFN-α plus ribavirin combination therapy also developed the condition.