Date of Award

January 2022

Document Type


Degree Name

Medical Doctor (MD)



First Advisor

Matthew Grant


Background: Pyomyositis and infectious myositis are rare infectious syndromes that affect skeletal muscle. The epidemiology of these syndromes has changed in recent decades.

Methods: In an effort to characterize pyomyositis and infectious myositis, we conducted a single-center retrospective study. Forty-three cases of pyomyositis and eighteen cases of infectious myositis were identified.

Results: Two-thirds of patients were men, and the mean age was 48 years. Diabetes mellitus was common (33%). Roughly half of all infections were due to staphylococcal species. Muscle pain (95%) was nearly universal, with subjective fever (49%) being common. The symptom constellation also included altered mental status in 16% cases. Antimicrobial therapy was used for a median of 18 days. Procedural interventions were often utilized to drain focal collections of infected fluid to obtain source control, and several patients (28%) underwent >1 procedure. Twelve cases had pathology specimens available, and 83% (10 of 12) were abnormal. The treatment success rate was 84%. Three deaths were attributable to muscle infections.

Conclusions: Staphylococci accounted for a large proportion of cases, but several atypical causes of pyomyositis or infectious myositis were identified. The majority of patients required both antimicrobial therapy and a procedural intervention. Studies which prospectively evaluate treatment modalities are indicated.


This thesis is restricted to Yale network users only. This thesis is permanently embargoed from public release.