In chronic masticatory muscle myositis, what histopathologic change occurs?

In chronic masticatory muscle myositis, what histopathologic change occurs?

• A. Masticatory muscle is replaced by fibrous tissue
• B. Fat infiltration of the masticatory muscle
• C. Inflammatory infiltration without fibrosis
• D. Hypertrophy of the masticatory muscle

Answer: (A)

In chronic masticatory muscle myositis the defining change is fibrous replacement of the affected muscles. Ongoing immune injury leads to myofiber damage and regeneration that shifts toward collagen deposition, so normal muscle fibers are gradually replaced by dense connective tissue. This fibrotic remodeling stiffens the jaw muscles and reduces function. Early or active disease may still show inflammatory cells and necrosis, but in the chronic stage fibrosis is the predominant histologic finding. Fat infiltration can occur in some chronic conditions, but it’s not the main feature here, and hypertrophy is not typical.

In chronic masticatory muscle myositis the defining change is fibrous replacement of the affected muscles. Ongoing immune injury leads to myofiber damage and regeneration that shifts toward collagen deposition, so normal muscle fibers are gradually replaced by dense connective tissue. This fibrotic remodeling stiffens the jaw muscles and reduces function. Early or active disease may still show inflammatory cells and necrosis, but in the chronic stage fibrosis is the predominant histologic finding. Fat infiltration can occur in some chronic conditions, but it’s not the main feature here, and hypertrophy is not typical.