desmin
Summary
Desmin is a type III intermediate filament protein found in muscle cells (skeletal, cardiac, and smooth muscle), where it forms the cytoskeletal scaffolding that connects myofibrils to the sarcolemma and nuclear membrane. Immunohistochemical staining for desmin is a key diagnostic tool used to confirm myogenic origin of tumors, particularly rhabdomyosarcoma and leiomyosarcoma. Mutations in the desmin gene cause a group of disorders called desminopathies, leading to skeletal and cardiac myopathies.
Detail
Desmin is the primary intermediate filament of muscle tissue, forming a three-dimensional scaffold around the Z-discs of sarcomeres in skeletal and cardiac muscle, and along the length of smooth muscle cells. It links myofibrils to each other, to the sarcolemma (via costameres), to the nuclear envelope, and to mitochondria, maintaining structural integrity and facilitating mechanical force transmission during contraction. In pathology, immunohistochemistry for desmin is used as a specific marker to identify tumors of muscle origin. Rhabdomyosarcoma (skeletal muscle origin, common in children) stains strongly positive for desmin along with myogenin and MyoD1. Leiomyosarcoma and leiomyoma (smooth muscle tumors) are also desmin-positive, along with smooth muscle actin (SMA). This helps differentiate these tumors from other spindle cell or small round blue cell tumors (e.g., Ewing sarcoma, lymphoma, neuroblastoma) which are desmin-negative. Clinically, mutations in the DES gene encoding desmin cause desminopathies (also called desmin-related myopathies), a subset of myofibrillar myopathies. These present with progressive skeletal muscle weakness (often distal initially), cardiomyopathy (dilated or restrictive), and cardiac conduction abnormalities/arrhythmias due to desmin aggregation and disruption of the cytoskeletal network. Desmin-related cardiomyopathy can present with heart failure or sudden cardiac death from arrhythmia. On muscle biopsy, desminopathies show characteristic eosinophilic granulofilamentous aggregates and desmin-positive inclusions.
Sources
- Robbins and Cotran Pathologic Basis of Disease
- Rubin's Pathology
- Kumar, Abbas, Aster - Pathologic Basis of Disease
- First Aid for the USMLE Step 1
Reviewed by AnkiBoss editorial — medical student review. Information here is for study reference only and is not medical advice. Spotted an error? Let us know.