Acquired hemophilia A is a rare bleeding disorder caused by autoantibodies against factor VIII (FVIII). Spontaneous bleeding in the various sites and severity is the most common clinical presentation. Here, we report a 74-year-old Thai woman with HIV infection who presented with spontaneous ecchymoses. The laboratory revealed isolated activated partial thromboplastin time prolongation with low FVIII activity and a presence of FVIII inhibitor. She was diagnosed with acquired hemophilia A. Corticosteroid monotherapy was the treatment regimen for inhibitor eradication. We demonstrate the clinical course of the rare condition and review the relevant literature.