Immune-mediated necrotizing myopathy with anti-signal recognition particle antibodies, in a patient with melanoma treated with BRAF/MEK inhibitors.

The effect of serine/threonine-protein kinase B-Raf/mitogen-activated protein kinase (BRAF/MEK) inhibitors on the immune system is not clearly described, but rare cases of autoimmune phenomena have been reported. The clinical case we present below is the first report of a necrotizing myopathy related to dabrafenib/trametinib treatment. A 48-year-old man started dabrafenib/trametinib for stage IV BRAF-V600E mutated cutaneous melanoma. After the first month, he presented with grade 3 pyrexia (Common Terminology Criteria for Adverse Events [CTCAE] v.5.0.) and increased creatinine-kinase levels. A diagnosis of immune-mediated necrotizing myopathy, antisignal recognition particle (anit-SRP) positive, was made. At disease progression, dabrafenib/trametinib was restarted, triggering a new episode of grade 2 pyrexia and myositis. Treatment was changed to encorafenib/binimetinib without repeating pyrexia or limiting creatinine-kinase elevation, presenting even a loss of anti-SRP antibodies. Given the temporal relationship, the fact that re-exposition induced a new worsening of the myopathy and the loss of the anti-SRP antibodies after changing treatment, we infer that there possibly is a clear relationship between dabrafenib/trametinib treatment and the myopathy.