A 77‐year‐old female was referred to our clinic in July 4,2008 with a week history of rapidly progressive necrotic skin lesions on her right fingers. She had been under treatments of mixed connective tissue disease(MCTD)since 1991. Laboratory findings revealed prolongation of activated partial thromboplastin time(aPTT)and the presence of lupus anticoagulant. We diagnosed this case as MCTD followed by antiphospholipid syndrome(APS). After the treatment of Prostaglangin E1and Sarpogrelate hydrochloride, low dose of oral aspirin was started. Necrotic lesions of her fingers improved gradually, and she was discharged in September21. APS should be considered when we see rapidly progressive necrotic skin lesions on patients with collagen deseases