Considering that i) an adrenal crisis is rare; ii) that most physicians and rheumatologists are aware of the long-term adverse events associated with GC therapy; and iii) that the 2009 EULAR recommendations and the 2010 BSR and BHPR guidelines for the management of GCA do not mention ACTH testing; we cannot recommend systematically performing this test during withdrawal of GCs. The gene discussed is POMC; the disease is acute adrenal insufficiency.