An Unusual Manifestation of Calcineurin Inhibitor-Induced Pain Syndrome in Kidney Transplantation: A Case Report and Literature Review

Objective: Unusual clinical course Background: Calcineurin inhibitors (CNI) are the mainstay immunosuppressive drugs for kidney transplantation. Although they provide excellent allograft and patient outcomes, adverse effects are frequently encountered. Calcineurin inhibitor-induced pain syndrome (CIPS) is a rare adverse effect of CNI. Previous case reports with CIPS diagnosis involved incapacitating pain in the lower extremities. Case Report: In this article, we report the first case of CIPS with severe back pain as the presenting symptom, which was correlated with a high tacrolimus trough concentration due to a drug interaction with clotrimazole troche. Magnetic resonance imaging (MRI) of the spine showed bone marrow edema, which is consistent with previous case reports. The patient's symptoms resolved within 3 weeks of the onset of pain. Treatments were symptomatic care and lowering the tacrolimus trough concentration. Pain was improved significantly with pregabalin but not with nifedipine. Conclusions: We reviewed the literature of kidney transplant cohorts with CIPS to ascertain prevalence, pain characteristics, and treatment outcomes. Apart from our case, all patients experienced lower extremities pain and were pain-free during the follow-up period, without any residual abnormalities. CIPS is a benign but adverse effect of CNI. Counselling patients about the disease's natural history and supportive care remain the best treatment.