Afebrile Recurrent Cellulitis Complicated by Linezolid-Induced Lactic Acidosis in an Elderly Patient

BACKGROUND Cellulitis typically presents with erythema, swelling, warmth, and systemic signs such as fever and leukocytosis. In older adults, immunosenescence and multimorbidity can blunt classical inflammatory responses, delaying diagnosis and complicating care. Linezolid, while effective against resistant gram-positive organisms, carries a risk of mitochondrial dysfunction and lactic acidosis during prolonged therapy. CASE REPORT We describe the case of an 87-year-old Puerto Rican woman with multiple comorbidities who experienced 4 hospitalizations in 6 months for recurrent cellulitis. Despite having visible inflammation, she consistently remained afebrile and without leukocytosis. Laboratory findings demonstrated a persistently elevated C-reactive protein level and erythrocyte sedimentation rate. Wound cultures revealed polymicrobial organisms, including Pseudomonas aeruginosa, Klebsiella pneumoniae, and Stenotrophomonas maltophilia. Broad-spectrum antibiotics were used, including linezolid at 600 mg twice daily, with an estimated total exposure of approximately 8 weeks across hospitalizations and outpatient treatment. Renal and hepatic function were monitored and remained stable throughout. Ultrasound imaging did not reveal abscess or osteomyelitis. During the final hospitalization, she developed lactic acidosis (lactate 2.5-3.1 mmol/L), in the absence of shock or hypoxemia, suggesting linezolid-induced mitochondrial toxicity. The patient died 2 days after discharge. CONCLUSIONS This case underscores the diagnostic challenges of afebrile cellulitis in frail older adults and the importance of careful antimicrobial stewardship. Clinicians should maintain vigilance for linezolid-induced lactic acidosis during extended therapy, particularly in patients with atypical presentations. The integration of biomarker trends into decision-making, prioritization of preventive strategies, and coordination of geriatric care are essential to improve outcomes in this vulnerable population.