Abstract
BACKGROUND
A growing number of patients with cancer receive checkpoint inhibitor (CPI) based immunotherapy. Peripheral nervous system toxicities including myositis, myasthenia gravis and inflammatory neuropathy are distinct from their non immunotherapy-related equivalents, with unique clinical presentations and therapeutic considerations.
METHODS
Patients with CPI myositis and non-fatigable ptosis were identified, and clinical data was retrospectively extracted from the electronic medical record in compliance with MD Anderson Cancer Center Institutional Review Board guidelines.
RESULTS
14 patients were identified. Average maximum creatine kinase (CK) was 3571 U/L (range 20-19,794). 9 patients had electromyography and nerve conduction studies documented in our system; all had electrodiagnostic evidence of myopathy and two had evidence of concomitant myasthenia gravis by electrodecrement. Two muscle biopsies revealed myositis with inflammatory T-cell infiltrate. 6 had positive anti-striated muscle antibody titers, 9/14 had concomitant myocarditis, 2 had hepatitis, 2 had pneumonitis and 1 had thyroiditis. All received high dose steroids, 11 received plasma exchange, 4 received rituximab, 4 received tacrolimus and 2 received tocilizumab. 7/14 patients died (50%). Mean time from initial neurology consultation for symptoms to death was 6.46 months (range .3-24). 5 patients had documented clinical stabilization or mild improvement on post-discharge follow-up.
CONCLUSIONS
While ptosis in patients receiving CPI can initially suggest myasthenia gravis, in patients with rapid onset and ultimately fixed deficits there should be a high index of suspicion for immunotherapy related restricted localized myositis. Myositis may coincide with other toxicities, such as myocarditis and pneumonitis, and can be fatal despite aggressive treatment. Deficits persist on post-discharge follow-up, suggesting protracted recovery for patients who survive.
Granulomatous Myositis Associated with Extremely Elevated Anti-striated Muscle Antibodies in the Absence of Myasthenia Gravis
