Pyomyositis

Symptoms

The disease progresses through three phases. The invasive stage, lasting about ten days, involves general muscle soreness and swelling without erythema, along with low-grade fever.

After 2–3 weeks, the purulent-suppurative stage brings increased body temperature and muscle tenderness. The third stage involves sepsis, which can lead to serious complications including death. Commonly affected muscles include the serratus anterior, pectoralis major, biceps, abdominal muscles, spinal muscles, glutei, iliopsoas, quadriceps, and gastrocnemius.

Epidemiology

Pyomyositis typically stems from a Staphylococcus aureus infection. While it can strike any skeletal muscle, it most commonly targets large muscle groups like the quadriceps or gluteals. First identified in 1885, this condition primarily affects children, especially those between two and five years old, though it can appear at any age. Minor injuries often precede the infection.

It is far more prevalent in tropical regions, where it accounts for 4% of hospital admissions. In temperate areas like the United States, pyomyositis was once rare, occurring in about 1 in 3,000 pediatric admissions, but its frequency has risen with the emergence of the USA300 MRSA strain. The disease is closely linked to living in the tropics, particularly northern Uganda, which reports 400 to 900 cases each year. In such areas, those affected typically have no other underlying conditions.

In temperate zones, however, it usually appears in people with weakened immune systems, chronic kidney failure, or rheumatoid arthritis. A rare form, gonococcal pyomyositis, is caused by Neisseria gonorrhoeae.

Did You Know?

• Abscesses within the muscle must be drained surgically, though not all patients require surgery if no abscess is present.
• Antibiotics such as vancomycin, teicoplanin, tigecycline, daptomycin, or linezolid are given for a minimum of three weeks.
• In some cases, co-trimoxazole is sufficient for treatment.