Drug-induced autophagic myopathies: Exploring pathophysiology with immunolabelling and proteomics

Hydroxychloroquine (HCQ), chloroquine (CQ), and colchicine are widely used to treat autoimmune and inflammatory diseases but can cause toxic autophagic vacuolar myopathies. This study investigates the pathological mechanisms of HCQ/CQ- and colchicine-induced myopathies through integrated clinical, histopathological, ultrastructural, and proteomic analyses. Nine patients with clinicopathologically defined toxic myopathy (HCQ/CQ, n = 4; colchicine, n = 5) were included. Muscle biopsies were analyzed using histoenzymology, immunohistochemistry for autophagic and immune markers, electron microscopy, and proteomic profiling in selected cases. Clinically, both groups presented with proximal muscle weakness and myalgia after variable drug exposure. Histology revealed rimmed and non-rimmed vacuoles, especially in HCQ/CQ cases, and myofibrillar disorganization; the latter predominated in colchicine-treated patients. Electron microscopy confirmed myofibrillar disruption in colchicine-treated patients and autophagosomes with curvilinear bodies in HCQ/CQ cases. Immunohistochemistry showed MHC-I upregulation, heterogeneous C5b-9 deposition, and accumulation of LC3 and p62, with evidence of endoplasmic reticulum stress and transcriptional dysregulation by GRP170 overexpression and cytoplasmic MeCP2 redistribution. Proteomic analysis revealed a shared molecular signature involving immune activation, extracellular matrix remodeling, cytoskeletal stress, mitochondrial dysfunction, and dysregulation of the autophagy-lysosome pathway. Overall, HCQ/CQ- and colchicine-induced myopathies converge on common mechanisms of autophagic impairment, immune activation, and disrupted muscle homeostasis.