CASE REPORT: Pyomyositis in the Setting of Chemotherapy-Induced Pancytopenia: A Rare Complication of Germ Cell Tumour Treatment

Introduction Spontaneous pyomyositis is an uncommon but serious infectious complication that typically occurs in immunocompromised patients and is more frequently reported in association with haematological malignancies. It’s occurrence in patients with solid organ tumours receiving systemic chemotherapy is rare and to date has not been described in the setting germ cell tumours. Case Presentation We report the case of a 50-year-old male with metastatic mixed germ cell tumour who developed pyomyositis following completion of four cycles of etoposide and cisplatin chemotherapy. Post-treatment, he developed severe pancytopenia complicated by fever, significant unilateral lower limb pain, and swelling. Initial imaging demonstrated multiple rim-enhancing intramuscular lesions, raising concern for metastatic disease versus abscess formation. Despite normalised tumour markers and no evidence of disease on restaging imaging, the radiological appearance remained equivocal. Image-guided biopsy and aspiration were therefore performed, yielding purulent material that cultured Staphylococcus aureus , with histopathology confirming benign inflammatory changes and no evidence of malignancy. The patient was successfully treated with oral antibiotics, with complete radiological resolution of lesions and no evidence of tumour relapse on follow-up. Conclusion This case represents, to our knowledge, the first reported instance of pyomyositis occurring in a patient with metastatic mixed germ cell tumour following chemotherapy. It highlights the importance of considering pyomyositis and spontaneous intramuscular haematoma as differential diagnoses in patients presenting with painful limb swelling in the setting of chemotherapy-induced pancytopenia, and underscores the diagnostic challenges in distinguishing infection from metastatic disease.