A Serious Complication of Allogeneic Stem Cell Transplantation: Relapsing Pseudomonas aeruginosa Panniculitis

A 58-year-old female following an allogeneic stem cell transplant (alloSCT) presented with tender subcutaneous nodule in the axillary and inguinal regions. One of the nodules was biopsied and cultured. The patient was diagnosed with Pseudomonas aeruginosa (P. aeruginosa) panniculitis. Blood cultures were negative for P. aeruginosa. The patient responded to 4 weeks of imipenem-cilastatin and gentamicin treatment but relapsed immediately after the discontinuation of antibiotic treatment with a change in the susceptibility of P. aeruginosa to antibiotics. The patient received piperacillin-tazobactam and aztreonam with no recurrence for nine months. Differential diagnosis of subcutaneous nodules can be difficult in an alloSCT setting. P. aeruginosa should be kept in mind, and the biopsy and culture of a nodule should be obtained without delay. Blood cultures can be negative. Despite long term antibiotic treatment, relapse can occur.