Protein S deficiency associated to anti-protein S antibodies in a patient with mixed connective-tissue disease and its reversal by danazol.

We describe here a female patient with mixed connective tissue disease, secondary antiphospholipid syndrome, pulmonary hypertension and severe acquired, probably autoimmune, antibody-mediated type I coagulation protein S deficiency (total, free and C4bp-bound). No previous instance of anti-PS antibody-associated PS deficiency had been reported. The patient was treated initially with prednisone, but the protein S levels did not rise until danazol was added, and dropped again after its withdrawal.