Background Pyomyositis is a bacterial infection of skeletal muscles, most commonly caused by staphylococcus aureus. If diagnosed early, pyomyositis can be treated with antibiotics alone. However, the diagnosis is often overlooked, or delayed because of lack of familiarity with this disease. Clinical suspicion and appropriate imaging techniques are the keys to early diagnosis.

Objectives To report a new case of pyomyositis, demonstrating the value of computed tomography (CT) in the early diagnosis and follow-up of pyomyositis.

Methods Retrospective clinical and laboratory analysis of one patient.

Results A previously healthy 44-year-old Caucasian workman developed chills and high fever, about 6 h after an abrasion of the skin over his right hand. Three days later he was admitted to the hospital with hyperthermia (41°C) and prostration. Physical examination revealed an exquisite tenderness of the right subclavicular area with local warmth, swelling and erythema of the skin, indicating acute inflammation in the chest wall. No evidence of suppuration, cellulitis, lymphangitis, or regional lymphadenopathy was observed in the right upper extremity. Laboratory investigation showed an erythrocyte sedimentation rate of 47 mm, a white blood cell count of 17,380/mm³ with 84% polymorphs, and a creatine phosphokinase of 1,520 IU/L (normal range 24–234 IU/L). Multiple blood cultures were negative and chest X-rays were normal. A CT scan of the chest demonstrated marked swelling of the right pectoralis minor muscle. This evidence of acute muscle inflammation supported the presumptive diagnosis of acute pyomyositis, in its invasive stage. Intravenous antibiotics therapy with a combination of clindamycin and ticarcillin/clavulanic acid was started on admission. Fever, tenderness, and other signs of inflammation subsided in a few days with antibiotics alone. No surgical procedure was necessary. After two weeks of hospitalisation the patient was discharged in good condition, but antibiotics were continued oraly for two more weeks. Complete clinical recovery with restoration to normal of all laboratory tests was achieved within one month. A new CT imaging taken four weeks later revealed a complete resolution of the inflammation with no residual deformity of the affected muscle, verifying the favourable outcome of prompt antibiotic treatment.

Conclusion Although the causative microorganism was not identified, there is convincing evidence that this patient had pyomyositis. This case illustrates the value of CT in timely diagnosis and nonsurgical management of pyomyositis, by showing that: a) CT imaging can allow early detection of pyomyositis during its presuppurative phase, b) prompt antibiotic therapy may obviate surgery, and c) besides facilitating an early diagnois, CT is also very useful in the follow-up of pyomyositis.