Stepwise Incremental Dose Schedule of Sirolimus Is Successfully Tolerated by a Patient With Lymphangioleiomyomatosis Who Was Initially Allergic to mTOR Inhibitors

Lymphangioleiomyomatosis (LAM) is a rare disease involving the proliferation of LAM cells in the lungs and the axial lymphatic system and mechanistic target of rapamycin (mTOR) inhibitors are the only effective medicines for treating it. Patients suffering from LAM, who are allergic to mTOR inhibitors can be treated by desensitizing them to the medicine. A 39-year-old woman presented with dyspnea caused by chylous pleural effusion, ascites, and retroperitoneal lymphangioleiomyomas. She was diagnosed with LAM based on the presence of LAM cell clusters (LCCs) in chylous pleural effusion and elevated serum vascular endothelial growth factor D (VEGF-D) concentration. She was allergic to cedars and yellowtails. Although she was started on sirolimus for treating LAM, the drug had to be discontinued on day 45 because of the appearance of a skin rash on her trunk. A year later, another oral mTOR inhibitor, everolimus, was initiated but had to be discontinued because of the appearance of cutaneous reactions. Since mTOR inhibitors are the only effective molecular-target medicines for LAM, desensitization to sirolimus was attempted by initiating exposure to sirolimus at a low dose followed by stepwise dose escalation. Eventually, the patient tolerated a dose of 0.5 mg/day of sirolimus, which resulted in a trough concentration of approximately 2 ng/ml in blood, without adverse cutaneous reactions; furthermore, clinically relevant effects were observed as her LAM condition reduced and stabilized. This case study illustrates that mTOR inhibitor therapy for LAM should not be abandoned because of allergic cutaneous reactions. Physicians must find a dose that balances adverse events and therapeutic effects to ensure continued treatment for patients with LAM. Furthermore, the possible mechanisms for mTOR inhibitor-induced cutaneous reactions have been discussed.