Brain heterotopias are rare congenital malformations embryologically related to encephaloceles. They present as a mass in or about the nose (nasal glioma) or in the nasopharynx. We present the clinical and pathological features of 5 cases of heterotopic brain tissue. Four nasal gliomas consisted of mature neuroglial tissue, including neurons in 2 cases, embedded in a fibrovascular stroma. A nasopharyngeal brain heterotopia showed histologic features of mature neuroglial tissue including neurons and ependymal-lined cystic structures. The finding of mature neuroglial tissue in a mass from the head and neck region raises three differential diagnostic possibilities: teratoma, encephalocele, or heterotopic tissue. A teratoma can be ruled out by examination of the entire specimen. Encephaloceles and brain heterotopias can be distinguished only after correlation with the patient's clinical and radiologic findings.

We describe the clinical and pathological findings of the hemolytic uremic syndrome (HUS) in two children with human immunodeficiency virus (HIV) infection. Both patients presented with microangiopathic hemolytic anemia, thrombocytopenia, and subsequently developed renal failure. The diagnosis of HUS was confirmed by renal histopathology in both patients. None of these children presented with bloody diarrhea, evidence of circulating antibody response to Escherichia coli O157 lipopolysaccharide, or other known risk factors for HUS, except for the presence of HIV infection. Each patient was treated with intravenous plasma infusion and renal replacement therapy. Their clinical course was characterized by non-oliguria and lack of significant hypertension throughout the acute phase of the disease. Despite these favorable clinical parameters, both patients developed end-stage renal failure. The etiology of this atypical HUS characterized by poor renal survival remains unknown and the role of HIV infection in its pathogenesis, although possible, is unclear.

We report a case of cystic hygroma and diffuse lymphangiectasia detected by sonogram at 12 weeks' gestation. Fetal karyotype was normal. At 20 weeks' gestation, herniation of the bowel into the chest was noted. At delivery, the infant was diagnosed as having Fryns' syndrome. This is the first reported case of Fryns' syndrome presenting with cystic hygroma.

Encephalopathy, leukoencephalopathy, and secondary parkinsonism occurred in 3 children with refractory leukemia undergoing allogenic bone marrow transplantation (BMT) who were treated with high-dose amphotericin B for pulmonary aspergillosis or sinus aspergillosis that did not involve the nervous system. Treatment included high-dose cytosine arabinoside, cyclophosphamide, and total body irradiation prior to the BMT. The children developed a progressively worsening encephalopathy and parkinsonian features, characterized by resting tremor, cogwheel rigidity, and masklike facies. Neuroimaging studies showed cerebellar, cerebral, and basal ganglia atrophy, as well as frontal and temporal lobe white matter involvement. Two of the 3 patients recovered, although 1 has residual intellectual impairment. The third succumbed to non-central nervous system Epstein-Barr virus-lymphoproliferative disease and had autopsy-confirmed leukoenephalopathy.

Identical allelic deletion at 11p13 in all components of the sporadic Wilms' tumors examined suggests that the stromal tissue components are neoplastic rather than non-neoplastic. In conjunction with variable WT1 gene expression in the different histologic components, the results raise the possibility that undifferentiated blastemal cells are the precursors of the stromal and heterologous elements. Morphologically benign stromal and heterologous elements may therefore be derived from neoplastic cells. The developmental state of the various tissue components of Wilms' tumor may be attributed to an altered residual WT1 gene that is required for the maturation of blastemal and epithelial cells but that is not required for the maturation of stromal and heterologous elements.

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