Pasireotide-resistant Refractory Cushing's Disease without Somatostatin Receptor 5 Expression

Pasireotide, which has a high affinity for somatostatin receptor (SSTR) 5, has attracted attention as a new treatment for refractory Cushing's disease. The patient was a 28-year-old man. He had refractory Cushing's disease and underwent multiple surgeries, radiotherapy, and medication therapy. An examination of the adenoma by immunohistochemistry revealed a low SSTR5 expression. An USP8 mutation was not detected by reverse transcription polymerase chain reaction. Although we administered pasireotide, it was ineffective. While a further investigation is necessary, the analysis of SSTR5 expression may support the prediction of the efficiency of pasireotide for Cushing's disease. We report this case as a useful reference when considering whether or not to use pasireotide for refractory corticotroph adenomas.