Role of electron microscopy in the diagnosis of nonneoplastic renal disease in children.

To assess the role of electron microscopy in the evaluation of pediatric renal biopsies, all native kidney biopsies performed in children for nonneoplastic renal disease over a 2-year period were reviewed. Of 80 biopsies, the role of electron microscopy was classified as "essential" in 50 (63%), "supportive or confirmatory" in 18 (23%), and "noncontributory" in 9 (11%), with no glomeruli available for study in 3 (4%). The role of electron microscopy with respect to indication for biopsy and final diagnosis is discussed. This study confirms the continued importance of electron microscopy in the evaluation of pediatric renal biopsies.

BK virus nephropathy in the native kidneys of a pediatric heart transplant recipient.

BK virus is a human polyoma virus that may cause nephropathy in immunosuppressed patients. It is a well-recognized cause of renal allograft dysfunction and allograft loss in renal transplant recipients, but it is an infrequent cause of nephropathy outside this setting. There are a few case reports of BK virus nephropathy in the native kidneys of immunosuppressed adult patients with non-renal transplants, but so far it has not been reported in pediatric non-renal solid organ transplant recipients. We report a case of a seven-yr-old heart transplant patient who was diagnosed with BK virus nephropathy, eight months after his second heart transplant. Despite intervention, his renal dysfunction progressed to renal failure. He is currently receiving maintenance hemodialysis and awaiting renal transplantation. It is important to recognize BK virus infection as a possible cause of renal dysfunction in immunosuppressed children who are non-renal transplant recipients.

Mycophenolate mofetil in pediatric renal transplantation: non-induction vs. induction with basiliximab.

North American Pediatric Renal Transplant Cooperative Study (NAPRTCS) reports have shown anti-T cell antibody, OKT3, to be deleterious in pediatric renal transplant recipients treated with mycophenolate mofetil (MMF). Unlike OKT3, basiliximab is a chimeric monoclonal antibody to the alpha subunit of the interleukin-2 receptor on activated T-lymphocytes. We sought to examine the outcome of MMF with or without basiliximab induction therapy in pediatric renal transplantation. Between January 1998, and June 2001, 49 pediatric renal transplants were performed at our center and 41 met the criteria for this study. We retrospectively analyzed the records of 25 patients who received MMF, Prednisone, CSA or TAC, alone (group I) and 16 patients who received MMF, CSA or TAC, and Prednisone in combination with basiliximab (group II). The two groups were similar with respect to recipient or donor age, gender, ethnicity, donor source (LD vs. CAD), cold ischemia time, and primary diagnosis. The basiliximab group had a shorter follow up period because of its more recent addition to our pediatric immunosuppression protocol, 12.9 +/- 5.9 months vs. 35.5 +/- 7.2 months for group I (p < 0.0001). At 6 months, the acute rejection rate was 16% (group I) compared with 25% (group II) (p = 0.689). The patient and graft survival at 6 and 12 months were 100% respectively for both groups. Basiliximab was well tolerated without significant adverse events. At 6 months, there was no significant difference between the groups in the incidence of urinary tract infection or cytomegalovirus infection. These data suggest that in the short-term, MMF with or without basiliximab induction therapy appears to yield excellent and statistically similar outcomes. However, further controlled studies are necessary to verify these findings as well as to define the role of basiliximab in MMF-treated pediatric renal transplant recipients.

Usefulness of immunohistochemistry in delineating renal spindle cell tumours. A retrospective study of 31 cases.

AIMS: To assess the usefulness of immunohistochemistry in delineating tumour diagnoses on a series of morphologically diagnosed renal spindle cell tumours (RSCTs). METHODS AND RESULTS: Formalin-fixed paraffin-embedded tissues from 31 morphologically diagnosed tumours were reinterpreted in light of newly obtained immunohistochemical information. By morphology, six had originally been classified as sarcomatoid carcinoma, five as spindle cell tumour (NOS), four as sarcoma (NOS), three as leiomyoma, three as leiomyosarcoma, and one each as fibrous polyp, hamartoma, neurilemmoma, mesoblastic nephroma, medullary fibroma, angiomyolipoma, haemangiopericytoma, malignant rhabdoid tumour, malignant Triton tumour, and carcinosarcoma. The application of immunohistochemistry verified the original diagnosis in 18 cases (18/31, 58%), confirming the diagnosis of sarcomatoid renal carcinoma (4/6), leiomyoma (2/3), leiomyosarcoma (3/3), sarcoma (NOS) (2/4), carcinosarcoma (1/1), malignant rhabdoid tumour (1/1), malignant Triton tumour (1/1), fibrous polyp (1/1), mesoblastic nephroma (1/1), hamartoma (1/1), and angiomyolipoma (1/1). Different tumour designations were suggested in 13 cases (13/31, 42%), including carcinosarcoma, sarcoma (NOS), leiomyosarcoma, solitary fibrous tumour, monomorphic/biphasic angiomyolipoma, endometrial stromal tumour, and congenital mesoblastic nephroma. CONCLUSIONS: Our data indicate that although morphology is most important in formulating the initial differential diagnosis, the addition of immunohistochemistry is vital in arriving at the correct classification of RSCTs.

Identification of connexin43 (alpha1) gap junction gene mutations in patients with hypoplastic left heart syndrome by denaturing gradient gel electrophoresis (DGGE).

Gap junction channels formed by the connexin43 protein are considered to play crucial roles in development and function because they allow the direct cell-to-cell exchange of molecules that mediate multiple signaling events. Previous results have shown that connexin43 channels are intricately gated by phosphorylation and that disruption of this regulation gives rise to severe heart malformations and defects of laterality in human, chick and frog. Here we report the identification of connexin43 gene mutations that represent a minor population of connexin43 alleles, which could be reliably detected by using denaturing gradient gel electrophoresis (DGGE) to visualize normal and mutant DNAs that were separately sequenced. In contrast, sequencing of total PCR products without DGGE-pre-selection failed to consistently identify these mutations. Forty-six controls and 20 heart transplant recipients were examined in this study. In the latter group, 14 children had hypoplastic left heart syndrome (HLHS) in which connexin43 gene defects were detected in eight. The remaining six transplant patients with HLHS and all controls showed no defects. All eight HLHS children with gene defects had the same four substitutions: two that were silent polymorphisms, and two that were missense, replacing arginine codons at positions 362 and 376 with codons for glutamines. All four of these substitutions are identical to the nucleotide sequence of the connexin43 pseudogene, suggesting the possibility of an illicit recombination. A breakpoint region was identified 5' to the mutation site in a 63bp domain that is 100% identical in the gene and pseudogene. Results from in vitro phosphorylation indicate that the absence of arginines 362 and 376 completely abolishes phosphorylation in the connexin43 channel regulation domain suggesting a possible mechanism for the pathologies associated with HLHS.

Naumoff short-rib polydactyly syndrome compounded with Mohr oral-facial-digital syndrome.

A stillborn baby boy had findings of severe constitutional dwarfism with short limbs, short ribs, and polydactyly that were consistent with Naumoff (type III) short-rib polydactyly syndrome. He also had additional congenital anomalies, including cleft palate, notching of the upper lip, small tongue with accessory sublingual tissue. These oral and pharyngeal anomalies were consistent with Mohr (type II) oral-facial-digital syndrome. We suggest the stillborn infant represented a compound of Naumoff short-rib polydactyly syndrome (SRPS-III) and Mohr oral-facial-digital syndrome (OFDS-II).

Langerhans' cell histiocytosis presenting with an intracranial epidural hematoma.

An 8-year-old boy developed vomiting and severe headache following minor head trauma. A CT scan of the head demonstrated a lytic lesion of the skull and adjacent epidural hematoma. Surgical evacuation and removal of the skull lesion and hematoma were carried out, and pathologic evaluation resulted in a diagnosis of Langerhans' cell histiocytosis (LCH). Epidural involvement of Langerhans' cell histiocytosis is very rare, and we report the first case of LCH presenting as an intracranial epidural hematoma.

Congenital disseminated malignant rhabdoid tumor: a distinct clinicopathologic entity demonstrating abnormalities of chromosome 22q11.

The clinical, pathologic, and immunohistochemical features of a widely disseminated tumor with rhabdoid phenotype are described in nine infants < or = 3 months of age. Five neonates had tumor evident at birth, two of which had placental metastases. The average survival following diagnosis was < 6 weeks. None of the infants had an apparent primary tumor in either the kidney or brain. In four cases, the dominant mass involved the head and neck region, and in two cases, the primary mass was paraspinal. The histologic features were those of a high-grade, round cell neoplasm with abundant cytoplasm and containing cells with cytoplasmic filamentous inclusions. Immunohistochemical studies revealed polyphenotypic antigen expression. Genetic information was available from eight of nine cases. Karyotype analysis revealed abnormalities of chromosome band 22q11-12 in three of six tumors. Fluorescence in situ hybridization studies or molecular studies demonstrated 22q11.2 deletions in all five cases with available frozen tissue, two of which had translocations involving 22q by karyotype analysis. The similar clinical and pathologic findings in these rapidly fatal tumors in infants and the demonstration of abnormalities of chromosome 22q11 in a majority of the cases supports their histogenetic and nosologic relationship to the family of malignant rhabdoid tumors that typically occur in young children in several anatomic sites, including kidney, soft tissues, liver, and brain. Like neuroblastoma and rhabdomyosarcoma, malignant rhabdoid tumor can appear as disseminated disease at birth or shortly thereafter.

Prolonged discordant xenograft survival and delayed xenograft rejection in a pig-to-baboon orthotopic cardiac xenograft model.

OBJECTIVE: Our objectives were to study delayed xenograft rejection and the effectiveness of pretransplantation total lymphoid irradiation combined with immunosuppression on rejection in a pig-to-baboon cardiac xenograft model. METHODS: Baboons were treated with pretransplantation total lymphoid irradiation, cyclosporine A (INN: ciclosporin), and methotrexate. Orthotopic pig-to-baboon cardiac transplantations were performed after depletion of circulating xenoreactive natural antibody by pretransplantation donor organ hemoperfusion. Tissue samples were collected for immunologic and immunopathologic evaluation. RESULTS: Pig cardiac xenografts survived more than 18 and 19 days without evidence of hyperacute rejection. Immunologic analysis of serum samples demonstrated that circulating xenoreactive natural antibody levels did not return to pretransplantation levels. The production of xenoreactive natural antibodies from the recipient's splenocytes was inhibited completely. Histologic examination of xenografts showed the feature of acute vascular rejection. Immunohistochemical studies demonstrated infiltration of cardiac xenografts by large numbers of macrophages, small numbers of natural killer cells, and a few T cells. The infiltrating macrophages also showed expression of interleukin-1 and tumor necrosis factor. Diffuse deposition of immunoglobulin G, C1Q, C3, and fibrin on xenograft vasculature was observed. Interleukin-2 expression was not found in rejected cardiac xenografts. Xenograft endothelial cells also showed evidence of activation (expression of cytokines interleukin-1 and tumor necrosis factor). CONCLUSIONS: This study demonstrates prolonged discordant cardiac xenograft survival and delayed xenograft rejection in a pig-to-baboon model. The delayed xenograft rejection is mediated by both humoral and cellular mechanisms. Pretransplantation total lymphoid irradiation combined with cyclosporine A and methotrexate can inhibit xenoreactive natural antibody production but not elicited antipig antibody production and the xenoreactivity of macrophages.

Handling and evaluation of pediatric renal tumors.

Optimal pathologic evaluation of pediatric renal tumors, which share many features in common with their adult counterparts, also includes some relatively unique considerations, in large part related to specialized classification, grading or staging systems, and ongoing collaborative clinical and biologic studies. Important factors in the gross evaluation, procurement of tissue for special studies, and selection of tissue blocks for light microscopy are briefly reviewed.

Prolonged discordant cardiac xenograft survival in newborn recipients.

BACKGROUND: We previously demonstrated very low levels of xenoreactive natural antibodies in newborns, suggesting the possibility of prolongation of xenograft survival in newborn recipients. We used a pig-to-newborn goat heterotopic cardiac xenograft model to examine our hypothesis that hyperacute rejection would be absent in newborn recipients and that both humoral and cellular rejection would participate in the late phase of discordant xenograft rejection. METHODS AND RESULTS: The serum of newborn goats was found to have very low titers of natural anti-pig antibodies. Newborn pig hearts were transplanted heterotopically into the neck of four unmanipulated newborn goats: none of these xenografts underwent hyperacute rejection. Dilation of the xenografts and decreased contractility were observed 4 to 6 days after transplantation, and the xenografts eventually ceased functioning between 6 and 8 days after transplantation. Blood samples collected after transplantation demonstrated a dramatic increase in anti-pig xenoantibody titers and correlated with histological studies demonstrating features consistent with delayed humoral rejection, including reactive vascular endothelial and perivascular stromal cells, marked capillary congestion, and interstitial hemorrhages. Scant to diffuse perivascular and interstitial infiltration of activated lymphoid cells occurred. CONCLUSIONS: Our study demonstrates that hyperacute rejection does not occur, allowing limited prolongation of xenograft survival in a pig-to-newborn goat cardiac xenograft model. We propose that this is attributable, at least in part, to the very low titers of natural antibodies in newborn recipients. Delayed xenograft rejection, however, remains an important problem in these newborn recipients. This delayed xenograft rejection is likely the result of both humoral and cellular rejection mechanisms.

Use of electron microscopy and other special techniques in the investigation of suspected specimen contamination.

Contamination of a biopsy or surgical specimen with spurious tissue is an uncommon but potentially disastrous event. In this regard, the case of a 5-year-old boy referred for treatment of an abdominal tumor is presented. Sections made from paraffin blocks brought by the family showed both neuroblastoma and a spindle cell sarcoma, initially suggesting the possibility of divergent or mixed differentiation. However, the resemblance of the spindle cell component to well-differentiated leiomyosarcoma rather than rhabdomyosarcoma raised the suspicion that a specimen contamination had occurred. Electron microscopy was instrumental in confirming the smooth muscle nature of the sarcomatous component, leading to a fluorescence in situ hybridization study, which established that this component was incompatible with the patient's gender. This case illustrates that even when the light microscopic differential has been compromised by specimen mishandling, electron microscopy can at times provide useful information regarding specimen identity, as well as assist in sorting out the correct diagnosis.

Primitive neuroectodermal tumor in a child with tuberous sclerosis.

The case of a 13-year-old boy with tuberous sclerosis and primitive neuroectodermal tumor of bone is presented. A pathogenetic association between these two entities is postulated, the unifying underlying mechanism being a maldevelopment of the neural crest, or neurocristopathy.

Limitations to survival for infants with hypoplastic left heart syndrome before and after transplant: the Loma Linda experience.

Untreated, hypoplastic left heart syndrome is a lethal cardiac defect. Heart transplant has become an accepted therapeutic option for this condition. However, significant limitations to survival remain for infants with this condition who are referred for heart transplantation. Attention to the prevention, early detection, and management of common problems occurring at each stage of the transplantation process is important for improving survival rates. This study retrospectively reviewed the cases of 195 infants with hypoplastic left heart syndrome registered for heart transplantation at Loma Linda University Medical Center between November 1985 and July 1996 to determine causes of death. During the waiting period, progressive cardiac failure and complications from interventional procedures were the leading causes. In the early postoperative period, technical issues and acute graft failure were most important, whereas late deaths (more than 30 days after transplant) were most often related to rejection and posttransplant coronary artery disease.