Page 259 - AIDSBK23C

Page 259

Kaposi's sarcoma has been reported in children with AIDS in both skin and visceral sites,
but with far less frequency than in adults with HIV. The etiology of KS probably involves
infection with human herpes virus 8 (HHV-8), but risk factors may be difficult to identify. The
average age of onset is between 5 and 6 years.[1055]
Next in frequency are smooth muscle tumors. These are either leiomyomas or
leiomyosarcomas. Leiomyosarcoma is one of the most common cancers in children with HIV
infection. These smooth muscle tumors are generally visceral in location (gastrointestinal tract,
lung, spleen, and liver). In lung, these lesions appear as multiple nodules; tracheobronchial
involvement may lead to respiratory distress with wheezing. Gastrointestinal lesions may
produce bloody diarrhea, abdominal pain, and obstruction.[588,589] Epstein-Barr virus can be
demonstrated in the cells of HIV-associated smooth muscle neoplasms, and EBV stimulated
clonal proliferation may contribute to their pathogenesis in both children as well as adults.[1056]
Histologic findings include interlacing fascicles of spindled smooth muscle cells with elongated,
blunt-ended nuclei and eosinophilic cytoplasm. Those that appear benign have a uniform cell
population and little or no mitoses; malignant-appearing leiomyosarcomas are densely cellular,
with pleomorphic, hyperchromatic nuclei and many mitoses. There may be collections of
primitive round cells with irregular nuclear contours that, on immunohistochemistry have a
smooth muscle phenotype, including positivity for smooth muscle actin and desmin. In some
cases, a variable T-cell inflammatory infiltrate is present.[589]

MISCELLANEOUS FINDINGS.-- An arteriopathy has been described at autopsy in
children dying of AIDS in which there is either cerebral vasculitis or generalized fibrocalcific
change in elastic lamina or media of arteries in brain, lung, heart, thymus, kidney, spleen, heart,
and lymph node. Pathologic findings in large vessels consist of vasa vasora medial involvement
with chronic inflammation. Coronary artery involvement is mainly calcific. The luminal
narrowing may explain focal necrosis, atrophy, fibrosis, or gliosis.[1057,1058] In the brain, this
arteriopathy is manifested as a diffuse dilation with ectasia of major arteries of the circle of
Willis, with intimal fibroplasia, medial thinning, and elastic lamina destruction or reduplication.
This arteriopathy can lead to hemorrhages in cerebrum, basal ganglia, and subarachnoid space.
Infarctions may also occur. Though little inflammation is identified within these lesions at
autopsy, the features suggest a prior vasculitis, and there is often a history of a prior
opportunistic infection, particularly varicella zoster virus (VZV).[1059,1060]
Human immunodeficiency virus-associated nephropathy (HIVAN) can occur in children.
Patients have excessive proteinuria or albuminuria. Classic features of nephrotic syndrome may
be present. Focal and segmental glomerulosclerosis (FSGS) is seen along with mesangial
hyperplasia, microcystic tubular lesions, or minimal change. The course in children is less
fulminant than in adults, but progression to end-stage renal disease can still occur. A fatal form
of hemolytic-uremic syndrome (HUS) has been described, but with more insidious onset and
without the diarrhea characteristic for the classic HUS related to shiga toxin.[1061]
The thymus in pediatric AIDS can undergo marked involution with irreversible injury
that contributes to immunosuppression and rapid progression of disease from immune
dysfunction. This occurs more often in children with HIV strains using CXCR4 as a coreceptor.
Aggressive antiretroviral therapy may lead to thymic recovery in children without extensive
thymic damage.[1062]
Candida infection of the esophagus or lung has been seen in 10% of pediatric cases.
Recurrent oral thrush, a frequent finding in infants with AIDS, may give rise to invasive or