Relation to Immunosuppressants?

A 35-y-old woman with pyrexia of unknown origin was referred to the Nuclear Medicine Department for an 18FFDG PET scan. She had undergone heart–lung transplantation for secondary pulmonary hypertension 4 mo previously. After transplantation she developed organizing pneumonia proven on transbronchial biopsies for which she required treatment with pulsed methyl prednisolone. Three months after surgery, she developed intermittent pyrexia with daily spikes of temperature up to 38.5°C. Her lung function was normal, and repeated bronchoscopy and transbronhial biopsies at that time revealed no evidence of rejection or persistent pneumonia. The chest radiograph and CT scan showed carinal and paratracheal lymphadenopathy (Fig. 1). On the clinical suspicion of lymphoproliferative disorder, she underwent a mediastinotomy and lymph node sampling, which revealed normal reactive lymph nodes with no evidence of malignancy. The whole-body PET scan demonstrated an irregular increase in tracer activity in the mediastinum consistent with the clinical suspicion of lymphoma (Fig. 2). In addition, markedly increased uptake was present in almost all major muscle groups, including those of the neck, thorax, pelvis, abdomen, and the extremities (Fig. 2). There were no obvious morphologic changes in these muscles on CT. The patient’s medication at the time of PET included the immunosuppressants tacrolimus and mycophenolate mofetil in addition to lansoprazole and pravastatin sodium. There was no history of hyperglycemia, insulin administration, or noticeable muscle activity before imaging. The plasma creatinine kinase (CK) remained normal before and after the PET study. A repeated bronchoscopy showed a large polypoid mass in the right upper lobe bronchus, which, on biopsy, confirmed high-grade B-cell posttransplantation lymphoproliferative disease.