Diagnosis>Organ System>

CLINICAL

• Most common cause of weakness and disability with AIDS is muscle atrophy and wasting from nutritional deficiency and repeated infections.
• 3 most common primary muscle disorders in HIV are HIV myopathy, idiopathic polymyositis and myopathy due to toxicity from NRTIs. Less common primary muscle disorders include lymphoma, inclusion body myositis, and infections such as toxoplasmosis.  
•  Myalgias, muscle tenderness and weakness of the proximal muscles are common features of all primary muscle disorders in HIV. Inclusion body myositis spreads to include distal muscles as well.
•  Differentiating among the many etiologies of primary muscle disorders is difficult. Empiric treatment and retrograde Dx common.
•  Infectious causes of myopathy must be ruled before empiric immunosuppression. These include pyomyositis by Staph. aureus and Toxoplasma. Pyomyositis usually presents with localized tenderness and swelling more than weakness; toxoplasmosis presents insidiously with diffuse muscle wasting and weakness similar to non-infectious etiologies.
•  Secondary causes of muscle weakness and tenderness include rhabdomyolysis, involvement in non-Hodgkin's lymphoma, cocaine abuse, trauma and seizures. These can present in all stages of HIV infection.

DIAGNOSIS

• Evaluate for general systemic features such as fever, arthralgias, or rash, including thorough neurological examination with detailed evaluation of involved muscles to look for localized muscle infections.
• CD4 count does not correlate with HIV myopathy but is low in infectious myopathies.
• Reflexes usually preserved in primary myopathy. Involvement of reflexes suggests an additional neuropathy (decreased reflexes) or spinal cord dysfunction (increased reflexes).
• Serum CPK elevated > 10x normal in HIV myopathy and in several of other etiologies. Follow CPK levels to monitor resolution. Aldolase does not add additional information. Lactase occasionally elevated and usually follows CPK levels.
• In both HIV myopathy and polymyositis, EMG reveals increased insertional activity, fibrillations and polyphasic potentials.  In NRTI-associated myopathy, EMG may show mild myopathic changes or may be normal.
• Muscle Bx may reveal pathology. Bx with HIV myopathy and polymyositis shows CD8+ T lymphocytes in endomysium. Evidence of HIV viral infection of muscle tissue rare in HIV myopathy. NRTI-associated myopathy usually unremarkable except in cases involving high doses of AZT, which can cause mitochondrial myopathy with "ragged-red" fibers. Intracellular cysts containing T. gondii confirms Dx of toxoplasmosis.
• Compile complete drug Hx, including use of AZT, illicit drugs, and statins..

TREATMENT

• Pyomyositis: broad spectrum ABx +/- surgical drainage may be needed. 
• HIV myopathy/idiopathic polymyositis: long-term corticosteroids, dose 1 mg/kg/d with gradual taper if CD4 <200.   Alternative: IVIG 0.4 mg/kg/d x 5 days on monthly basis.
• NRTI-associated myopathy: discontinue NRTI and follow CPK levels. If levels do not return to normal within 1-2 mos, HIV myopathy or polymyositis should be suspected. For NRTI-associated myopathy, NSAIDs may provide symptomatic relief and carnitine may prevent development of myopathy if administered concurrently with NRTI.
• Rhabdomyolysis: stop offending agent; IV hydration to prevent renal failure.
• HIV-associated wasting: see wasting module.
• Toxoplasmosis: Primary regimen is combination of pyrimethamine (200 mg loading dose followed by 50-75 mg daily) plus sulfadiazine (4-6 g daily). Patients with sulfa intolerance can substitute clindamycin (600 mg 4 times daily) for sulfadiazine. Leucovorin or folic acid with pyrimethamine therapy will prevent bone marrow toxicity.

FOLLOW UP

• Monitor CPK monthly during treatment of muscle disorders.
• Muscle strength examination. May use dynamometer: gives objective values on weakened muscles.
• Monitor renal function with high CPK and during IVIG therapy.
• Corticosteroid therapy: monitor for complications, including OIs. Use OI prophylaxis based on CD4 count.
• Discontinue therapy when asymptomatic and CPK normal for >3 mos.
• Taper steroids slowly over 1-2 mos.

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