Version July 2025
Frozen muscle sections from a patient with hydroxychloroquine-induced myopathy.
(A) H&E stain showing muscle fibers harboring vacuoles of various sizes, some of which contain granular material.
(B) Acid phosphatase: increased reactivity (red, large, darker color spots) in several muscle fibers. Some vacuoles (arrow) are filled with acid phosphatase positive material.