A heterogenous collection of disorders characterized by the abnormal structure or functioning of skeletal muscle.

Patience often have symptoms of fatigue, exercise intolerance, generalized weakness, and muscle pain.

Many symptoms are non-specific and may reflect non myopathic conditions, including cardiopulmonary disorders, Orthopedic conditions, rheumatologic diseases, medication use, deconditioning, and even depression.

Suspicions of an underlying myopathy include discrete patterns of muscle weakness, fatigable weakness, muscle atrophy, myotonia, and recurrent myoglobinuria.

Evaluation includes the duration of symptoms and history including developmental and early childhood history as well as a family history of similar symptoms or diagnosis of myopathy.

There are congenital metabolic, and mitochondrial myopathy that may present at birth or early childhood, with associated issues of failure to thrive, delayed motor milestones, and contractures.

Other hereditary or acquired myopathies may not be sent until adolescence to adulthood.

Inflammatory myopathies, such as polymyositis and dermatomyositis may occur at any age, while inclusion body myositis often presents in late adulthood.

Patients may develop symptoms after initiation of lipid-lowering medications and may experience and acquired medication induced myopathy, while those with symptoms after a carbohydrate-rich meal may have periodic paralysis.

For patients with a positive family history an attempt to determine the inheritance pattern can be a guide for future genetic testing and counseling.

There are 10 basic patterns of muscle weakness and allows clinicians to recognize and categorize patients and improve diagnostic accuracy.

Fixed weakness of the proximal limb – girdle muscles is the most common and least specific pattern of weakness in patients with underlying myopathies, such as limb-girdle Muscular Dystrophy and acquired myopathies.

Limb- girdle weakness of the upper extremities may manifest in patients having difficulty raising their arms to lift objects overhead, where as those with proximal weakness of the lower limbs may describe difficulty rising from a chair without pushing off with their arms.

Fatigable weakness which may be intermittent, may predominate in metabolic myopathies, periodic paralysis or other neuromuscular conditions such as myasthenia gravis, with return to normal strength levels between episodes.

Distal predominant weakness can occur in distal myopathy, metabolic myopathies, congenital myopathy, and myotonic and muscular dystrophies.

Distal predominant weakness is more commonly a sign of a length – dependent polyneuropathy.

A scalpuloperoneal distribution of weakness, affecting the proximal arms and distal legs, may be seen in patients with fascioscapulohumeral muscular dystrophy and other hereditary myopathies, and maybe associated with scapular winging.

The pattern of distal and proximal leg weakness is uncommon in myopathy, but is pathopneumonic for inclusion body myositis, particularly when asymmetrical and involving the finger flexors.

Patients with weakness of the cranial innervated musculature may present with ptosis, dysarthria, dysphagia, and Ophthalmoplegia.

Certain conditions may suggest an underlying myopathy, such as ocularparyneal muscular dystrophy or myotonic dystrophy, but may herald neuromuscular conditions, including myasthenia gravis and motor neuron disease.

Individuals with defective muscle relaxation that have a hereditary condition such as myotonia, para myotonia, or myotonic dystrophy.

Muscle power can be tested manually load by observation of functional ability of patients.

Evaluation includes the grading of strength of cranial innervated, proximal, and distal limb musculature so that comparative assessments can be done.

Creatine kinase levels cause the most useful initial laboratory studies and evaluation of a patient with a suspected myopathy.

Creatine kinase levels may be normal in patients with myopathy, as in those with slowly progressive disease, those with profound muscle atrophy, or patients using corticosteroid therapy.

Creatine kinase levels may be elevated in patients without myopathy such as those having heavy exertion or in patients with endocrinopathies such as hypothyroidism.

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