Diffuse tropical primary pyomyositis is an infrequent entity in our country, with few cases associated to community-acquired Methicillin- resistant Staphylococcus aureus. There are no reported cases of Community-Acquired Methicillin-Resistant Staphylococcus aureus (CA- MRSA) in Peru. We present the case of a 70 year old male with a previous diagnosis of type 2 diabetes mellitus, receiving irregular treatment, who was admitted to the hospital with a history of 10 days of low back pain radiating to the left leg, fever and forced fexion of the right hip due to pain during movement. The diagnosis of diffuse pyomyositis of both psoas muscles was performed with MRI and culture of a posterior paravertebral collection, from which Staphylococcus aureus resistant to oxacillin, penicillin and dicloxacillin was isolated.