Introduction: The primary muscle disorders are a diverse group of diseases; they are defined and classified in accordance with their clinical and pathological manifestations and the distribution of predominant muscle weakness, they involve different groups of diseases, including the muscular dystrophies, inflammatory myopathies, metabolic and congenital myopathies. Duchenne and Becker muscular dystrophy (D/BMD) are the most common member of muscular dystrophies.Objective: The aim of this study was to study primary muscular diseases in a series of Egyptian patients and detects a relative incidence of each disease.Methods: Muscle biopsy examination of 117 muscle biopsies of hypotonic patients of all ages that investigated in the neuromuscular pathology lab of the national institute of neuromotor disabilities during the period of 2003 till 2010. A final diagnosis was arrived at based on characteristic features on biopsy examination.Results: The result of muscle biopsy examination, and immunohistochemical study were added to the clinical, EMG and CPK data to give final diagnosis as follow; muscular dystrophies (71 cases), metabolic myopathy (26 cases), congenital myopathies (9 cases) and none classified myopathy (11 cases).Conclusion: primary muscle diseases in Egypt are a heterogeneous group of neuromuscular disorders in clinical practice and are often difficult to diagnose, resulting in under diagnosis and under reporting.