Page 193 - AIDSBK23C

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response. Muscle biopsy shows primary endomysial inflammation, red-rimmed vacuoles,
amyloid deposits, eosinophilic inclusions, and small round fibers in groups. Muscle fibers
express MHC class-1 antigens and are invaded primarily by CD8+ T-lymphocytes.[816]
Diffuse infiltrative lymphocytosis syndrome (DILS), a rare condition in HIV-infected
patients, is characterized by persistent CD8 hyperlymphocytosis and multivisceral CD8 T-cell
infiltration that results from a strong host response to HIV infection. DILS usually presents as
painless parotid enlargement, but extraglandular complications of DILS include facial palsy,
peripheral neuropathy, polymyositis, lymphocytic interstitial pneumonitis, renal tubular acidosis,
lymphocytic hepatitis, and lymphoma. In DILS, muscle lymphocytic infiltration is usually found
in the setting of peripheral neuropathy and/or inflammatory myopathy. Diagnostic criteria with
3
HIV infection include circulating CD8 hyperlymphocytosis at >1000/mm and histological
confirmation of CD8 T-cell infiltration in three different organs or tissues.[814] DILS appears to
be antigen-driven, and antiretroviral therapy is effective in treating it.[582]
Pyomyositis is a disease that is endemic to tropical regions, but can occasionally be seen
in conjunction with immunocompromised states, including HIV infection, in temperate climates.
Pyomyositis is a bacterial infection of skeletal muscle and is clinically marked by gradually
developing fever along with localized muscle pain, swelling, and tenderness. The lower
extremity is four times more likely than the upper extremity to be involved. Areas most often
affected include thigh, thigh with the calf, buttock, upper extremity, and iliopsoas. A history of
trauma may have preceded development of pyomyositis. CT imaging shows muscle swelling and
well-delineated areas of fluid attenuation with rim enhancement with contrast. T1-weighted MR
imaging shows higher signal intensity in involved muscles, with a rim of increased intensity at
the border of the involved region. On T2-weighted images, this rim is of low intensity with
gadolinium enhancement, whereas the affected muscle displays heterogeneous increased
intensity. Foci of homogeneous intensity usually correspond to fluid collections. Thickening of
fascial planes and reticulation of subcutaneous fat with overlying thickened skin may also be
seen. Leukocytosis may or may not be present. The serum creatine kinase may not be elevated.
Blood cultures may be positive in a sixth of cases. Staphylococcus aureus is the most common
organism cultured, followed by streptococci. Pathologically, there is extensive necrosis of
muscle with neutrophilic exudates. Pyomyositis is treated with antibiotics if diagnosed early, but
surgical incision and drainage in conjunction with antibiotic therapy are required for more
advanced cases.[817,818]
Acute rhabdomyolysis is uncommon but may occur at any stage of HIV infection,
manifesting as rhabdomyolysis in primary HIV infection, recurrent rhabdomyolysis, and isolated
rhabdomyolysis. Rhabdomyolysis at the end stage of AIDS may or may not be associated with
opportunistic infections of muscle. Antiretroviral drugs causing rhabdomyolysis in HIV patients
include didanosine, lamuvidine, raltegravir, tenofovir, and etravirine. The protease inhibitors
(PIs) ritonavir and delaviridine inhibit the cytochrome P450 3A4 isozyme (CYP3A4) hepatic
enzyme, and concurrent use of PIs and simvastatin or lovastatin that rely on CYP3A4 for
metabolism can increase statin levels and increase the potential for rhabdomyolysis. The
antibiotic combination trimethoprim-sulfamethoxazole has also been implicated in
rhabdomyolysis.[813,814]
Other skeletal muscle findings include atrophy with HIV wasting syndrome, marked by
reduction in lean body mass, while body fat stores are maintained. Muscle biopsy may show
diffuse atrophy, or type II atrophy, mild neurogenic atrophy, or thick-filament loss, without
conspicuous inflammation, as in other cachectic myopathies of other causes. Inflammatory