Iliopsoas Pyomyositis With Bacteremia at an Early Stage of Presentation in a Temperate Region.

A psoas abscess, a collection of pus in the psoas muscle, is rare but the incidence is increasing with the use of computed tomography (CT) and magnetic resonance imaging (MRI). Pyomyositis, a muscular infection that does not lead to abscess formation, is well known as tropical pyomyositis because it is highly prevalent in tropical areas. We encountered a case of iliopsoas pyomyositis and bacteremia without abscess formation. The blood culture was positive despite the early stage of presentation and no abscess formation on MRI. Imaging is the gold standard for diagnosing iliopsoas abscesses. There are cases similar to ours wherein the blood culture is positive before the formation of an abscess. Regardless of whether an abscess is found on MRI or not, we need to consider the possibility of false negatives at the early stage of presentation. A suspicion of this disease is essential during a physical examination for early diagnosis and treatment, especially in rural areas, where medical resources are limited. Furthermore, pyomyositis is a common disease in tropical regions, but in recent years, case reports of occurrences in temperate regions have increased. This case indicates the need to consider pyomyositis as a differential diagnosis of fever and hip joint pain even in temperate regions.