Diabetic Pyomyositis: A Forgotten Entity?—A Case Report

INTRODUCTION

First identified by Scriba in 1885, pyomyositis was historically endemic to tropical regions, but has recently seen increased incidence in temperate zones.¹ It accounts for 1–4% of hospitalizations in tropical areas. Normally, skeletal muscle resists bacterial infections, but in tropical pyomyositis, bacteria can invade during transient bacteremia from procedures like dental manipulations or urinary catheterizations, particularly under immunocompromised conditions.^2–4

Tropical pyomyositis is often misdiagnosed due to its nonspecific initial presentation, leading to unnecessary investigations, prolonged hospital stays, increased costs, and worsened prognosis if treatment is delayed. Late-stage complications include compartment syndrome, sepsis, and death. Long-term effects can involve osteomyelitis, muscle scarring, and significant functional impairment.

Immunodeficiency is a major factor in the development of pyomyositis. Conditions predisposing individuals include HIV, diabetes, chronic renal failure, primary immunodeficiency diseases, malignancy, immunosuppressant use, chemotherapy, organ transplants, and intravenous drug use. Malnutrition, blunt trauma, and intense exercise may also increase the risk.

CASE DESCRIPTION

A 56-year-old male from a remote village, employed as a sweeper, was referred to our diabetic clinic with poorly controlled diabetes and a diagnosis of “frozen shoulder.” Clinical examination revealed severe tenderness and swelling over the right shoulder and trapezius muscle, along with an elevated body temperature. The patient was admitted for further evaluation. Table 1 summarizes the relevant investigations conducted. Figure 1 depicts the presence of pus in the trapezius muscle as observed during the USG of the joint and muscle.

With the presentation in mind, a provisional diagnosis of primary pyomyositis due to uncontrolled hyperglycemia was made. The patient was planned for incision and drainage after proper glycemic control (Basal Bolus regimen). Approximately 50 mL of pus was aspirated from the trapezius muscle and sent for culture. The cultures revealed a growth of Staphylococcus aureus, sensitive to Piperacillin + Tazobactam and Clindamycin. The patient was put on injectable antibiotics for 2weeks.

His repeat blood work after 10 days of treatment revealed TLC – 6,300/cumm, CRP – 6, FBS 135 mg/dL and PPBS – 178 mg/dL. The tenderness and swelling had subsided, and the patient was afebrile.

DISCUSSION

The combined analysis of the clinical presentation, imaging, and laboratory values suggested that our patient had pyomyositis of the trapezius muscles. The treatment approach for pyomyositis typically depends on the stage of the disease at diagnosis.

According to studies by Larkin et al., Drosos, and Shepherd, the clinical presentation varies with the stage of the disease. This classification applies to both tropical and non-tropical pyomyositis, with the primary difference being geographical location:^5–7

• First Stage (“Invasive stage”): This stage lasts about ten days and is characterized by minimal signs of inflammation. Patients often present with low-grade fever, painful firm swelling, and crampy local muscle pain. Laboratory findings may include leukocytosis, anemia, and eosinophilia. Aspiration at this stage typically yields no pus. Treatment usually involves intravenous antibiotics such as clindamycin or vancomycin. This stage may resolve on its own or progress to the next stage.

• Second Stage (“Suppurative stage”): Occurring between 10 and 21 days after symptom onset, this stage presents with more pronounced signs of inflammation, including muscle tension, edema, high-grade fever, and significant leukocytosis. Over 90% of patients are diagnosed at this stage, benefiting from incision and drainage or needle aspiration of the abscess, as antibiotics alone are insufficient for symptom relief. Without treatment, the condition can advance to the final stage.

• Third Stage (“Late stage”): If untreated, the infection disseminates, causing the patient to become critically ill with high-grade fever and systemic toxicity, potentially leading to septic shock, acute kidney injury, and long-term complications. About 5% of patients present with such severe symptoms, necessitating comprehensive supportive management, including fluids, antibiotics, and surgical intervention.^8–10

Atypical presentations may occur in patients with HIV infection, diabetes mellitus, hematopoietic disorders, or other conditions impairing neutrophil function.¹¹ Diabetic patients with long-standing disease and poor glycemic control are particularly at risk due to compromised humoral and cellular defenses, as well as nerve and blood vessel damage.

Diagnosing pyomyositis can be challenging due to the nonspecific clinical features, which often overlap with common endemic febrile illnesses, leading to low clinical suspicion. Differential diagnoses include malaria, dengue, viral fevers, polymyositis, septic arthritis, osteomyelitis, cellulitis, lymphangitis, deep vein thrombosis, hematoma, tumors, synovitis, appendicitis, diverticulitis, and peritonitis.¹² Confirmation of diagnosis can be achieved through an abscess culture or a muscle biopsy.

CONCLUSION

Pyomyositis, an unfamiliar entity, may be fatal if not diagnosed early. The initial signs and symptoms are nonspecific, making it often underdiagnosed. A high level of suspicion is imperative in diabetic patients and/or patients with other types of immunocompromised states; mainly in the presence of fever and myalgia without significant elevation of muscle enzymes. It needs to be noted that, though Staphylococcus aureus is the most common causative organism, it may not always be detected in blood cultures. Prompt antibacterial treatment is vital in its management and surgical intervention which, when relevant, should not be postponed. The prognosis remains excellent if the disease is promptly identified and managed appropriately.

ORCID

Mainak Mandal https://orcid.org/0009-0002-7226-2598

Abhishek Chanda https://orcid.org/0009-0000-7731-5535

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