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

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.