Holoprosencephaly and interstitial deletion of 2(p2101p2109)

We report on a girl with holoprosencephaly and a small, de novo interstitial deletion of most of band 2(p21). The similarity between the cytogenetic findings and CNS malformations in our patient and those recently reported by Münke et al. [Am J Med Genet 30:929-938, 1988] suggests a phenotypic relationship between deletion of this band and holoprosencephaly.     

Thrombospondin in essential thrombocythemia

Essential thrombocythemia is a myeloproliferative disorder characterized by frequent bleeding and thrombotic complications. On a molecular level, two abnormalities of platelet thrombospondin have been identified: abnormal glycosylation of the intact 185,000-dalton chain has been detected and a shortened form of the thrombospondin chain is present. We have used two monoclonal antibodies and Lens culinaris lectin to probe the structure of thrombospondin in the platelets from three patients with essential thrombocythemia; one patient with polycythemia vera and two patients with secondary thrombocytosis. The presence of abnormal thrombospondin fragments with molecular weights of 160,000 and 30,000 was detected in the intact platelets and in the supernatant from thrombin-treated platelets, in all of the individuals except one of the secondary thrombocytosis patients. Monoclonal antibody binding studies indicate that both fragments are produced by proteolysis at a single site, which results in the removal of a 30,000- dalton fragment from the NH2-terminal. Lens culinaris lectin-binding studies revealed that some of the carbohydrate moieties of thrombospondin are near this cleavage site. The results are consistent with the hypothesis that the abnormal thrombospondin fragments observed under conditions of increased platelet production are due to increased susceptibility to proteolysis which, in turn, may be due to defective glycosylation.     

Cardiac rhabdomyomata and megacystis-microcolon-intestinal hypoperistalsis syndrome.

Multiple cardiac rhabdomyomata were discovered on necropsy tissue review of a previously well child with megacystis-microcolon-intestinal hypoperistalsis syndrome, who died unexpectedly at home at 40 months of age. Multiple cardiac rhabdomyomata occur rarely and have not previously been reported with this syndrome. They are most frequently associated with tuberous sclerosis. The finding of multiple cardiac rhabdomyomata in this patient suggests the possibility that these two rare conditions may be associated. Putative gene loci for tuberous sclerosis have been assigned to the long arms of chromosomes 9 and 11 and it is possible that the cardiac rhabdomyomata seen in this patient are a serendipitous indicator of the location of the megacystis-microcolon-intestinal hypoperistalsis gene.