Checkpoint inhibitors and arthritis: seeking balance between victories and defeats

Eventually, we heard the French proverb “ dans la medicine comme dans l’amour, ni jamais, ni toujours ” suggesting that medicine is unpredictable. The introduction of new therapeutic interventions in clinical practice accompanies this rule, arising both certainties and doubts, until experiences are shared to generate a conduit guide. However, just like any guide, medical guidelines should work as compasses, not as anchors, because real-life medicine constantly exposes physicians to new and unfamiliar situations, replete with previously unheard-of and unweighted variables.The introduction of immune checkpoint inhibitors (ICIs) in the treatment of cancer is an example of this situation. Despite these drugs are one of the greatest therapeutic advances of medicine in the last decades, positive points emerge and also negative ones, providing a cascade of new knowledge, including rheumatic immune-related adverse event (irAE) induced by ICI.1 2 We read with great interest a manuscript written by Chan and Bass in this journal reporting a case of polymyalgia rheumatica (PMR) induced by ICI therapy that was partially treated with a MEK 1/2 inhibitor, proposing a possible correlation between the MEK/ERK pathway and PMR.1 We emphasise that this was only allowed after the fortuity irAE associated with ICI therapy, coupled with the acumen of Chan and Bass to identify this possible correlation.In the last 2 years, countless publications have flooded the journals with case series addressing the rheumatic irAE associated with the ICI. In February 2018, a practical guideline about the management of those irAEs was published in the Journal of Clinical Oncology .3 This guideline brought a breath to those professionals who longed for a specific orientation regarding the management of all irAEs. Interestingly, the guideline separated the rheumatic manifestations into …