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Myopathies: Muscling Your Way to the Diagnosis
Sumaira Nabi, MBBS, FCPS Neurology | March 5, 2020
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Image courtesy of Wikipedia.
Myopathies: Muscling Your Way to the Diagnosis
Sumaira Nabi, MBBS, FCPS Neurology | March 5, 2020 | Contributor Information
There is a wide spectrum of disorders that affect the structure and function of muscles. These disorders, often collectively referred to as myopathies, can have a variety of clinical presentations.[1] Muscle weakness and fatigability are often the main features. Generally, patients present with symptoms suggesting proximal muscle weakness, such as difficulty in getting up from a sitting position, climbing stairs, combing hair, or reaching out for objects.
Myopathies: Muscling Your Way to the Diagnosis
Sumaira Nabi, MBBS, FCPS Neurology | March 5, 2020 | Contributor Information
Myopathies may be broadly classified into hereditary and acquired variants. Certain features (eg, age of onset, childhood features and birth history, family history, and pattern and rate of progression) can help distinguish between the two classes.
Image courtesy of Hanna Nomani.
Myopathies: Muscling Your Way to the Diagnosis
Sumaira Nabi, MBBS, FCPS Neurology | March 5, 2020 | Contributor Information
Thorough clinical evaluation is mandatory to differentiate myopathies from peripheral neuropathy, anterior horn cell diseases, and neuromuscular junction disorders. Cardinal features of myopathy on neurologic examination include the following:
Muscle bulk – Normal; wasted in advanced cases
Proximal muscle weakness – Positive Gower sign in some cases (shown)
Tenderness on palpation – Sometimes present
Tone – Normal; sometimes decreased in advanced cases
Deep tendon reflexes – Normal; hypoactive in advanced cases
Babinski sign – Negative
Sensory system – Typically normal
Stance – Lordosis, genu recurvatum
Gait – Waddling, tiptoe walking
Image courtesy of Sumaira Nabi, MBBS.
Myopathies: Muscling Your Way to the Diagnosis
Sumaira Nabi, MBBS, FCPS Neurology | March 5, 2020 | Contributor Information
A 25-year-old woman presents to the neurology clinic with complaints of muscle aches and progressive difficulty in climbing stairs, rising from a sitting position, and combing her hair. She reports no fever, joint pains, or rash. On examination, muscle power is 3/5 in the proximal muscle groups of both the upper and the lower extremities. Muscular bulk, tone, reflexes and sensations are normal. No skin rash is apparent. Assessment of muscle enzymes reveals marked elevation of creatine kinase (CK), aldolase, and lactic dehydrogenase (LDH) levels. Needle electromyography (EMG) of the upper and lower extremities reveals myopathic changes in all of the examined proximal muscles with fibrillation potentials (shown).
Which of the following is the most likely diagnosis?
Osteomalacia
Muscular dystrophy
Polymyositis
Dermatomyositis
Image courtesy of Medscape.
Myopathies: Muscling Your Way to the Diagnosis
Sumaira Nabi, MBBS, FCPS Neurology | March 5, 2020 | Contributor Information
Answer: C. Polymyositis.
Polymyositis is a subacute-to-chronic progressive weakness of proximal limb and axial muscles that has an insidious onset and predominantly affects women aged 30-60 years.[2] Besides weakness, patients may experience aching pain in the girdle muscles. In advanced cases, involvement of muscles of the neck, pharynx, and larynx leads to dysphagia and dysphonia. On laboratory testing, muscle enzymes (ie, CK, aldolase, and LDH) are markedly elevated, as in this case. Needle EMG reveals myopathic changes in all the proximal muscles with positive sharp waves and fibrillation potentials as a result of irritable muscle membranes. Muscle biopsy is crucial in diagnosing polymyositis, typically revealing extensive patchy destruction of muscle fibers with inflammatory changes (lymphocytes and plasma cells [shown]). This is thought to be a cell-mediated immune response against muscle fibers. Treatment involves long-term steroid therapy and immunosuppression.
Image courtesy of Medscape.
Myopathies: Muscling Your Way to the Diagnosis
Sumaira Nabi, MBBS, FCPS Neurology | March 5, 2020 | Contributor Information
A 35-year-old woman presents with a 2-week history of proximal muscle weakness, fever, myalgia, and rash. On examination, she has a maculopapular erythematous rash on the forehead, nose, cheeks, and hands (shown). On neurologic examination, muscle power is grade 3 at the shoulder and hip joints and grade 5 distally. Muscle bulk, muscle tone, and deep tendon reflexes are normal, and plantars are bilaterally flexors. The sensory system is intact. The respiratory, cardiovascular, and abdominal systems are normal. Muscle enzymes are markedly elevated. Needle EMG shows myopathic motor unit action potentials in all of the examined proximal muscles with positive sharp waves and fibrillation potentials.
Which of the following is the most likely diagnosis?
Dermatomyositis
Polymyositis
Rheumatoid arthritis
Systemic lupus erythematosus
Myopathies: Muscling Your Way to the Diagnosis
Sumaira Nabi, MBBS, FCPS Neurology | March 5, 2020 | Contributor Information
Answer A. Dermatomyositis.
Dermatomyositis is an acquired inflammatory myopathy that may be idiopathic or may be associated with certain malignancies or autoimmune diseases.
Images courtesy of Medscape | Dirk M Elston, MD (bottom right).
Myopathies: Muscling Your Way to the Diagnosis
Sumaira Nabi, MBBS, FCPS Neurology | March 5, 2020 | Contributor Information
The clinical features of dermatomyositis are the same as those of polymyositis, along with the following characteristic skin manifestations[3] (shown):
Heliotrope rash - Facial rash with eyelid edema
Gottron papules - Rash over the elbows, knuckles, and interphalangeal joints
Nail-fold telangiectasia
V sign - Rash over the front of the neck and shoulders
Shawl sign - Rash over the back of the shoulders and arms
This condition is thought to be a humorally mediated autoimmune disease affecting the muscles and skin.
Image courtesy of Maria-Magdalena Georgescu, MD, PhD, Louisiana State University/Shreveport.
Myopathies: Muscling Your Way to the Diagnosis
Sumaira Nabi, MBBS, FCPS Neurology | March 5, 2020 | Contributor Information
Muscle biopsy (shown) is definitive for diagnosis of dermatomyositis. Histopathologic assessment reveals perivascular or interfascicular inflammatory infiltrates (or both) with muscle fiber degeneration or regeneration (or both). In polymyositis, the infiltrates are mainly intrafascicular.
Image courtesy of Centers for Disease Control and Prevention.
Myopathies: Muscling Your Way to the Diagnosis
Sumaira Nabi, MBBS, FCPS Neurology | March 5, 2020 | Contributor Information
A 7-year-old boy presents with weakness and difficulty in walking, running, and climbing stairs. One of his maternal uncles is wheelchair-bound. On examination, the patient has calf pseudohypertrophy. Proximal muscle weakness is present, and the Gower sign is positive. The patient also has a waddling gait. His serum CK levels are 50 times higher than normal. Needle EMG shows myopathic changes. On muscle biopsy (shown), degeneration of muscle fibers is visible with proliferation of connective tissue and adipose tissue.
Which of the following is the most likely diagnosis?
Congenital myopathy
Duchenne muscular dystrophy (DMD)
Myotonia congenita
Mitochondrial myopathy
Image courtesy of Hanna Nomani.
Myopathies: Muscling Your Way to the Diagnosis
Sumaira Nabi, MBBS, FCPS Neurology | March 5, 2020 | Contributor Information
Answer: B. Duchenne muscular dystrophy (DMD).
DMD is the most common X-linked recessive muscular dystrophy and is a degenerative disease of the muscles.[4] It affects only males. The underlying genetic defect leads to failure to manufacture dystrophin, the gene for which is one of the largest genes in the body. There is progressive muscle wasting, usually manifesting between the ages of 3 and 5 years, which delays the achievement of motor milestones (shown). These patients eventually become wheelchair-bound, and cardiac or respiratory complications lead to premature demise. Genetic analysis and muscle biopsy are confirmatory. Histologic specimens show degeneration of muscle fibers with proliferation of connective tissue and adipose tissue. There is no known cure, but steroid drugs are thought to slow the progression of muscle weakness. In December 2019, golodirsen was approved by the US Food and Drug Administration (FDA) for the treatment of patients with a confirmed mutation of the DMD gene.
Image courtesy of Wikipedia.
Myopathies: Muscling Your Way to the Diagnosis
Sumaira Nabi, MBBS, FCPS Neurology | March 5, 2020 | Contributor Information
A 31-year-old man presents with a 2-year history of generalized weakness and stiffness. He also has difficulty in releasing his grip. One of his paternal cousins also has a similar illness. On examination, the patient's face appears long and narrow with hollowed cheeks, partial ptosis, and frontal baldness. He has atrophy of intrinsic muscles of the hands and feet on both sides. He also has clinical grip and percussion myotonia. His deep tendon reflexes are normal, as are his sensations.
Which of the following is the most likely diagnosis?
Myotonia congenita
Myotonic dystrophy
Becker muscular dystrophy
Drug-induced myopathy
Images courtesy of Hanna Nomani (bottom) and Sumaira Nabi, MBBS (top).
Myopathies: Muscling Your Way to the Diagnosis
Sumaira Nabi, MBBS, FCPS Neurology | March 5, 2020 | Contributor Information
Answer: B. Myotonic dystrophy.
Myotonic dystrophy is the most common muscular dystrophy in adults.[5] The mode of inheritance is autosomal dominant. The condition is characterized by a slowly progressive weakness of facial and neck muscles, which leads to the typical "hatchet-faced" appearance. Frontal balding, ptosis, and wasting of the sternocleidomastoid and temporalis muscles are apparent. Myotonia can be elicited in hand grip or percussion of the thenar muscles or tongue (shown). Myotonic dystrophy also has extramuscular dystrophic features, such as cardiomyopathy, hypogonadism, and diabetes mellitus. EMG shows typical myotonic discharges with the classic "dive-bomber" sound (shown). Genetic analysis yields a definitive diagnosis.
Image courtesy of Sumaira Nabi, MBBS.
Myopathies: Muscling Your Way to the Diagnosis
Sumaira Nabi, MBBS, FCPS Neurology | March 5, 2020 | Contributor Information
A 40-year-old man presents with a history of progressive loss of vision, diplopia, and drooping eyelids. On examination, the patient has bilateral asymmetrical partial ptosis and restricted eye movements in all cardinal directions of gaze, more so in the left eye than in the right. Visual acuity is markedly reduced, and bilateral pigmentary retinopathy is apparent on funduscopic examination. The rest of the systemic examination is unremarkable. Muscle biopsy reveals ragged red fibers on modified Gomori stain.
Which of the following is the most likely diagnosis?
Myasthenia gravis
Graves disease
Kearns-Sayre syndrome (KSS)
Orbital pseudotumor
Myopathies: Muscling Your Way to the Diagnosis
Sumaira Nabi, MBBS, FCPS Neurology | March 5, 2020 | Contributor Information
Answer: C. Kearns-Sayre syndrome (KSS).
Ophthalmoplegia and pigmentary retinopathy are the hallmark ocular findings in KSS.[6] This syndrome usually manifests before the age of 20 years. It is a genetic disorder characterized by mutations in mitochondrial DNA. A wide range of clinical abnormalities may occur, including endocrine dysfunction, growth retardation, mental slowness, and cardiac conduction defects. Diagnosis is based on molecular genetic testing and skeletal muscle biopsy, which reveals ragged red fibers on modified Gomori stain, as in this case. No specific or curative treatment is available for KSS. Management is directed primarily toward the complications of the syndrome, such as cardiac and endocrine involvement.
Image courtesy of Medscape.
Myopathies: Muscling Your Way to the Diagnosis
Sumaira Nabi, MBBS, FCPS Neurology | March 5, 2020 | Contributor Information
A 25-year-old woman presents with a 6-month history of progressive proximal muscle weakness. She also has a history of constipation and cold intolerance. On examination, her thyroid gland is enlarged. Laboratory workup reveals an elevated serum CK level. Thyroid hormone levels are very low. EMG shows myopathic changes (see slide 17). Muscle biopsy shows no inflammation. After thyroxine therapy, the patient's muscle weakness starts improving.
Which of the following is the most likely diagnosis?
Polymyositis
Dermatomyositis
Drug-induced myopathy
Hypothyroid myopathy
Image courtesy of Sumaira Nabi, MBBS.
Myopathies: Muscling Your Way to the Diagnosis
Sumaira Nabi, MBBS, FCPS Neurology | March 5, 2020 | Contributor Information
Answer: D. Hypothyroid myopathy.
Both hypothyroidism and hyperthyroidism are associated with myopathy.[7] Proximal muscle weakness is present in one third of patients with hypothyroidism. In addition, delayed relaxation of deep tendon reflexes and myotonia may be seen, as well as pseudohypertrophy of muscles. Serum CK is often markedly elevated. However, muscle biopsy does not show inflammation, in contrast to the typical findings with polymyositis. EMG shows small myopathic potentials with a rapid recruitment pattern (shown). Patients generally improve after receiving thyroid hormone replacement therapy.
Myopathies: Muscling Your Way to the Diagnosis
Sumaira Nabi, MBBS, FCPS Neurology | March 5, 2020 | Contributor Information
Hyperthyroidism is associated with a variety of muscular and neuromuscular disorders. In addition to proximal muscle weakness with brisk reflexes, patients with hyperthyroidism may exhibit hypokalemic periodic paralysis and myasthenia gravis. Thyroid ophthalmopathy is another well-known clinical entity. In hyperthyroid myopathy, serum CK levels are usually normal. Muscle biopsy may show nonspecific fiber atrophy. Once the patient becomes euthyroid with antithyroid therapy, the myopathy typically improves.
Image courtesy of Wikipedia.
Myopathies: Muscling Your Way to the Diagnosis
Sumaira Nabi, MBBS, FCPS Neurology | March 5, 2020 | Contributor Information
A 17-year-old woman presents with slowly progressive muscle weakness involving the proximal limbs. On examination, the patient is obese, with plethora, acne, hirsutism, and moon face. She also has striae on her abdomen. The serum CK level is within the normal range, and muscle biopsy shows no inflammatory changes. Serum cortisol levels are high. Computed tomography (CT) of the abdomen with contrast shows an adrenal mass. After resection of the tumor, the patient's muscle weakness improves.
Which of the following is the most likely diagnosis?
Steroid myopathy
Polymyositis
Drug-induced myopathy
Muscular dystrophy
Image courtesy of Hanna Nomani.
Myopathies: Muscling Your Way to the Diagnosis
Sumaira Nabi, MBBS, FCPS Neurology | March 5, 2020 | Contributor Information
Answer: A. Steroid myopathy.
Cushing syndrome is caused by excessive levels of adrenal steroids.[8] It is characterized by hirsutism, moon face, acne, truncal obesity, hypertension, impaired glucose tolerance, and osteoporosis. Patients with this syndrome may also have myopathy in the form of slowly progressive proximal muscle weakness. Serum CK levels are usually normal. Needle EMG may or may not reveal myopathic features. Muscle biopsy reveals type 2b fiber atrophy. Removal of the oversecreting gland improves muscle strength.
Image courtesy of Wikimedia Commons | James Heilman.
Myopathies: Muscling Your Way to the Diagnosis
Sumaira Nabi, MBBS, FCPS Neurology | March 5, 2020 | Contributor Information
A 29-year-old woman presents to the emergency department with sudden-onset paralysis. She has no respiratory or swallowing difficulty and is able to move her neck and facial muscles. There is no history of pain or paresthesia. There is no history of any recent diarrhea, cough, shortness of breath, or fever. The patient does have a history of episodic palpitations. Physical examination reveals flaccid paralysis of all extremities with diminished deep tendon reflexes. Sensations and cranial nerve function are grossly intact. Prominent U waves (shown) are visible on electrocardiography (ECG).
Which of the following is the most likely diagnosis?
Thyrotoxicosis
Neuropathy
Hypokalemic periodic paralysis (HPP)
Myopathy
Image courtesy of Wikimedia Commons | Miansari66.
Myopathies: Muscling Your Way to the Diagnosis
Sumaira Nabi, MBBS, FCPS Neurology | March 5, 2020 | Contributor Information
Answer: C. Hypokalemic periodic paralysis (HPP).
There are several types of periodic paralysis characterized by episodic flaccid paralysis. Of these, HPP is the most common, with a prevalence of 1 in 100,000.[9] The most peculiar feature of this condition is the sudden onset of weakness, which may range in severity from a mild, transient weakness to severe disability with respiratory failure. Defects in sodium and calcium ion channels results in low potassium levels and muscle weakness. The serum potassium level is usually low. ECG may reveal low-voltage complexes and U waves. Acute episodes are treated with potassium replacement; spironolactone, acetazolamide, and long-term potassium supplementation are used for prophylaxis.
Image courtesy of Pikrepo.
Myopathies: Muscling Your Way to the Diagnosis
Sumaira Nabi, MBBS, FCPS Neurology | March 5, 2020 | Contributor Information
A 45-year-old man presents with a 10-day history of severe generalized muscle pain and weakness. He also reports experiencing difficulty with walking, arising from a sitting position, and combing his hair. He has a history of hypertension and diabetes mellitus and has been on regular medication. Recently, his cholesterol was found to be high, and he started taking medication for this 3 weeks ago. On examination, the patient's muscles are tender with proximal muscle weakness. Deep tendon reflexes and sensations are intact. Investigations reveal a serum CK level of 13,000 U/L.
Which of the following is the most likely diagnosis?
Polymyositis
Inclusion body myositis
Dermatomyositis
Statin-induced myopathy
Image from Abdulrazaq M et al. Iran J Basic Med Sci. 2015 Aug; 18(8): 737–744. PMID: 26557961.
Myopathies: Muscling Your Way to the Diagnosis
Sumaira Nabi, MBBS, FCPS Neurology | March 5, 2020 | Contributor Information
Answer: D. Statin-induced myopathy.
Statins are lipid-lowering medications that play a vital role in primary and secondary prevention of ischemic heart disease and stroke. Muscle pain is a common side effect, reported by almost 15% of patients who take these agents.[10] In most cases, the muscle pain is benign, and there are no biochemical or histologic abnormalities that improve after the drug is discontinued. There are, however, some patients who have severe myopathies associated with muscle weakness, CK elevation, and muscle biopsy specimens showing inflammation and necrosis of muscle fibers. (The image in the slide shows [A] normal muscle, [B] muscle fiber disorientation and mild inflammatory cell infiltration, and [C] destruction and vaculation of muscle tissue.) This condition is known as statin-induced immune-mediated necrotizing myopathy (IMNM). Discontinuance of the statin does not lead to a significant drop in CK levels. Muscle biopsy shows inflammatory changes and necrotic muscle fibers, which are suggestive of IMNM. Serology shows a high anti-HMG-CoA reductase antibody titer (anti-3-hydroxy-3-methylglutaryl-coenzyme A reductase antibody), which is diagnostic of statin-induced IMNM. Treatment with corticosteroids and immunosuppressive agents is required. CK levels, muscle weakness, and pain improve gradually over a period of months.
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The emergence of a novel coronavirus (SARS-CoV-2 [2019-nCoV]) during a December 2019 outbreak of respiratory illnesses in Wuhan, China, has become a global public health emergency.Slideshows, February 2020
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Author
Sumaira Nabi, MBBS, FCPS Neurology
Senior Registrar and Consultant Neurologist
Department of Neurology
Pakistan Institute of Medical Sciences
Islamabad, Pakistan
Disclosure: Sumaira Nabi, MBBS, FCPS Neurology, has disclosed no relevant financial relationships.
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