Noninflammatory inclusion body myopathy

**Definition:** Noninflammatory inclusion body myopathy (IBM) is an idiopathic muscle disorder without inflammatory exudates and expression of class I major histocompatibility complex. Rimmed vacuoles and “IBM-like” filaments without inflammatory cells are described in muscle biopsy.

**Exclusions:** - Myasthenia gravis or certain specified neuromuscular junction disorders