Background <p>Melioidosis is endemic in Southeast Asia and northern Australia and can resemble various conditions. Soft tissue involvement is usually limited to localised cellulitis or superficial abscesses. Our case presented with diffuse cellulitis and deep intramuscular abscesses of the thoracoabdominal wall—an exceedingly rare manifestation mimicking necrotising soft tissue infection, a surgical emergency. Reporting such cases is essential to prevent misdiagnosis and unnecessary surgery in endemic settings.</p> Case presentation <p>A man in his sixties from southern Vietnam with previously undiagnosed diabetes mellitus presented with right upper quadrant and flank pain, high fever, and hypotension. Laboratory tests showed leukocytosis and elevated inflammatory markers. Ultrasound revealed gallstones and a positive Murphy’s sign. He was diagnosed with acute calculous cholecystitis and septic shock, and promptly started on intravenous meropenem before emergency laparoscopic cholecystectomy. However, his back pain progressively intensified after admission and became severe and disproportionate to examination findings. Within 30&#xa0;hours, he developed rapidly spreading erythema over the flank, back, buttock, and thigh. Necrotising soft tissue infection (NSTI) was suspected, with a Laboratory Risk Indicator for Necrotising Fasciitis (LRINEC) score of 7. Despite concern, he remained haemodynamically stable and inflammatory markers declined. MRI revealed diffuse cellulitis and multiple intramuscular abscesses involving thoracoabdominal and thigh muscles, including a large abscess in the right posterior thoracoabdominal wall. Blood cultures grew <i>Burkholderia pseudomallei</i>, confirming melioidosis. Meropenem was continued for four weeks, and oral trimethoprim–sulfamethoxazole was introduced. No surgical drainage was required. By day 6, pain and erythema improved. Follow-up MRI on day 10 showed reduced abscess size and improved cellulitis. At two-week follow-up, the patient remained asymptomatic, bedside ultrasound confirmed resolution, and he continued oral therapy to complete the three-month course.</p> Conclusions <p>This case underscores the importance of considering melioidosis in patients from endemic areas presenting with rapidly progressive soft tissue infections that mimic necrotising soft tissue infection. Early recognition and a structured diagnostic approach can help distinguish non-necrotising forms and avoid unnecessary surgery.</p> Clinical trial <p>Not applicable.</p>