Primary pyomyositis is an acute or subacute bacterial infection of skeletal muscle characterized by the formation of intramuscular localized abscess without a previous adjoining or remote infection. Although it is not frequent in our population, it is increasing because of community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) emergency. For an early diagnosis and to avoid secondary complications a high degree of clinical suspicion is required. We report a case of primary pyomyositis in a boy without an underlying condition or previous infection.