Primary pyomyositis of the psoas muscles in a temperate climate. Review of two cases in children followed up over the long term

Abstract

Background. We review two cases of primary pyomyositis of the psoas in children that occurred in Navarre, their management and long-term evolution. Primary pyomyositis of the psoas muscle is a rare infection in a temperate climate. Its diagnosis is difficult due to the similarity of the symptoms with several infectious processes, mainly septic arthritis of the hip in children and adolescents. The rarity of the present cases is due to several facts: occurrence in children, in a temperate climate (Navarre), immunocompetent patients and without subjacent pathology, besides their monofocal situation that is contrary to the more frequent multifocal presentation. These factors, besides the poor specificity of the symptoms, constitute a diagnostic challenge. Methods. We present two patients (10 and 12 years old) with fever and a painful hip. Neither of the patients had predisposing factors. Both of them showed hip flexion with limited range of motion in rotations. Confirmation of the diagnosis was made by ultrasound, CT-scan and/or MRI. Needle aspiration of the hip, under general anaesthesia, confirmed the reactive origin of the joint effusion in both patients. In neither of the two cases was there a significant diagnostic delay. Staphylococcus aureus was isolated in the purulent material in one case and in the hemoculture in the other. Both patients have been checked in a long-term revision (follow-up of 7 and 10 years). Results. They were successfully treated by isolated antibiotherapy in one case and surgical drainage in the other. Healing was achieved in each case without relapse or sequels in a long-term revision. We carry out a global revision of this rare infection, emphasising the difficulty of its clinical diagnosis and the different treatment modalities and the proper indication. We suggest an algorithm as a clinical guide for its clinical-therapeutic management.