Challenges in diagnosing hydroxychloroquine myopathy during the COVID-19 pandemic.

Hydroxychloroquine is being used for COVID-19 symptoms and in clinical trials, but can cause a toxic myopathy that leads to muscle weakness. A review of skeletal muscle biopsies from patients with hydroxychloroquine myopathy gives pointers of steps that can be taken to diagnose this toxic myopathy early and help differentiate it from COVID-19-related muscle weakness.