A deletion in the gene for glycoprotein IIb associated with Glanzmann's thrombasthenia.

The platelet fibrinogen receptor is composed of a complex of glycoproteins (GP) IIb and IIIa on the surface of platelets. Deficient function of this receptor prevents normal platelet aggregation, resulting in Glanzmann's thrombasthenia (GT). In this paper, we describe a black thrombasthenic patient who is either homozygous or hemizygous for a deletion within the GPIIb gene. Initial Western blot analysis of platelet proteins from this patient did not detect any GPIIb, but did detect small amounts of GPIIIa of normal mobility. Quantitation of vitronectin receptor (VNR) demonstrated that this thrombasthenic patient had approximately 1.5-2 times the number of these receptors per platelet compared with controls, a finding that has previously been noted in other thrombasthenic patients with defects in GPIIb. Genomic Southern blot studies demonstrated a deletion in the GPIIb gene of approximately 4.5 kilobasepairs (kb). Analysis of the isolated GPIIb gene demonstrated that the deletion begins between two Alu repeats within intron 1 and ends in intron 9. Polymerase chain reaction (PCR) studies using platelet RNA and oligonucleotides directed to both the 5' and 3' ends of the GPIIb cDNA sequence easily detected GPIIb transcript, suggesting that the genomic deletion of exons 2-9 does not significantly decrease the level of the GPIIb mRNA. Sequence analysis of PCR-generated GPIIb cDNA showed that a cryptic AG splice acceptor sequence was being utilized, resulting in a transcript that contained a portion of introns 1 and 9, as well as having a deletion of exons 2-9. Unlike the GPIIb gene, the GPIIIa gene appears to be intact by Southern blot analysis. PCR studies using platelet RNA and oligonucleotides directed to the GPIIIa cDNA sequence demonstrated the presence of GPIIIa mRNA. In summary, the thrombasthenic state in this patient appears to be due to a GPIIb gene deletion resulting in an abnormal transcript and no detectable platelet GPIIb. Platelet GPIIIa levels were secondarily low presumably due to the known instability of GPIIIa in the absence of GPIIb.

Evidence for a 17p tumor related locus distinct from p53 in pediatric primitive neuroectodermal tumors.

Primitive neuroectodermal tumors of the central nervous system are the most common malignant brain tumors in children. Cytogenetic analysis of these tumors has demonstrated alterations of chromosome 17, in particular isochromosome 17q, as the most frequent chromosomal abnormality detected. Since the consistent loss of a specific chromosomal region in a given tumor type most likely indicates the presence of a tumor related gene in that region, we undertook a combined molecular and cytogenetic approach to examine alterations of chromosome 17 in primitive neuroectodermal tumors. Seven of 14 tumors analyzed demonstrated loss of alleles for loci on 17p. In three of the seven tumors tested, a loss in copy number was observed for only the most telomeric locus on 17p13.3, D17S34. Limited sequence analysis of the same seven tumors did not reveal mutations in four highly conserved coding regions of the p53 gene. These data suggest a new tumor associated locus on 17p distinct from and distal to TP53, which is involved in the initiation or progression of at least a subset of primitive neuroectodermal tumors.

Preoperative history and coagulation screening in children undergoing tonsillectomy.

To evaluate the usefulness of preoperative screening for coagulation disorders in children, we prospectively studied laboratory and bleeding histories in 1603 children undergoing tonsillectomy. All patients had preoperative laboratory screening with a complete blood count, prothrombin time, activated partial thromboplastin time, and bleeding time. Persistent abnormalities on repeat testing 1 week later were investigated further by a standardized schema. A subset of 129 patients, including all those who bled perioperatively or had laboratory abnormalities, completed a standard historical questionnaire. Thirteen patients had persistent laboratory abnormalities diagnostic of lupus inhibitor (5), non-lupus inhibitor (6), mild hemophilia A (1), and vonWillebrand disease (1). Two patients had persistently prolonged activated partial thromboplastin times of undefined cause. Fourteen patients (10.8%) interviewed reported positive bleeding histories. Of these, five, including the patient with vonWillebrand disease, had persistent laboratory abnormalities. History alone failed to detect the patient with hemophilia A. For patients with inhibitors or prolonged activated partial thromboplastin times of unknown cause, surgery was delayed until the coagulation abnormalities resolved, and there was no perioperative bleeding. The patient with vonWillebrand disease had severe postoperative bleeding despite treatment with cryoprecipitate. In predicting perioperative bleeding, history and laboratory screening had a high specificity but a very low positive predictive value due to poor sensitivity and a low prevalence of bleeding. Some children with bleeding disorders may be identified first during routine preoperative coagulation testing, and replacement therapy or delay or cancellation of surgery may reduce or prevent perioperative hemorrhage. However, the large number of false positive laboratory tests and bleeding histories, coupled with the relative rarity of inherited and acquired coagulopathies, raises doubts about the overall value of routine screening.

Pulmonary metastases and bone sarcomas. Surgical removal of lesions appearing after adjuvant chemotherapy.

Pulmonary metastasis is the leading cause of death in pediatric patients with bone tumors. Multiple thoracotomies for surgical removal of individual lesions are performed at many centers. To explore the efficacy of this procedure and establish guidelines for an appropriate choice of patients, the experience with 43 thoracotomies in 24 children was reviewed. The appearance of first metastasis later than one year after diagnosis, presence of fewer than five nodules, and completeness of surgical resection were favorable predictors of postthoractomy survival. Early or multiple metastases, unresectable disease, and hilar, nodal, or pleural lesions conferred an unfavorable prognosis. With careful patient selection, pulmonary metastecotomy is a safe procedure that has few operative or long-term complications. It must be emphasized that although surgical removal of pulmonary metastases prolongs survival with good quality of life, the majority of patients with bone sarcomas ultimately succumb to their disease after thoracotomy. Follow-up time of greater than eight years is necessary to adequately assess the effectiveness of pulmonary resection in eradicating all disease in these patients.

Molecular analysis of a partial deletion of 22q in a central nervous system rhabdoid tumor.

We previously reported the non-random occurrence of monosomy 22 in rhabdoid or atypical teratoid tumors of the brain in three young children. We now present cytogenetic and molecular studies of an additional rhabdoid tumor with the karyotype 46,XX,-9,-22,+i(1q),+der(22)t(9;22)(p13;q11)/45,XX,-9,-10,- 22,+i(1q),+der(22)t(9;22)(p13;q11). These studies further demonstrate the involvement of chromosome 22, and they begin to define the critical region containing a gene or genes involved in the development or progression of rhabdoid tumors of the brain.

Ifosfamide-induced renal tubular dysfunction and rickets in children with Wilms tumor.

The renal tubular Fanconi syndrome developed in five patients with Wilms tumor after treatment with ifosfamide, a derivative of cyclophosphamide. Glomerular filtration rates were severely decreased. Renal function was investigated because of the development of rickets. All patients had undergone reduction of renal mass by nephrectomy. None had preexisting renal tubular injury. The syndrome developed at cumulative doses of ifosfamide of 39 to 99 gm/m2. Low serum bicarbonate and phosphate concentrations with glucosuria, aminoaciduria, and hypochloremic metabolic acidosis were the manifestations of the Fanconi syndrome. Bicarbonate and phosphate replacement resulted in bone healing, but recovery of tubular and glomerular function did not occur. Monitoring of these laboratory values during ifosfamide therapy could allow earlier replacement therapy to prevent severe bone disease.