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Morquio A syndrome (MPS IVA) is a systemic lysosomal storage disorder caused by the deficiency of N-acetylgalactosamine-6-sulfatase (GALNS), encoded by the GALNS gene. We studied 37 MPS IV A patients and defined genotype-phenotype correlations based on clinical data, biochemical assays, molecular analyses, and in silico structural analyses of associated mutations. We found that standard sequencing procedures, albeit identifying 14 novel small GALNS genetic lesions, failed to characterize the second disease-causing mutation in the 16% of the patients' cohort. To address this drawback and uncover potential gross GALNS rearrangements, we developed molecular procedures (CNV [copy-number variation] assays, QF-PCRs [quantitative fluorescent-PCRs]), endorsed by CGH-arrays. Using this approach, we characterized two new large deletions and their corresponding breakpoints. Both deletions were heterozygous and included the first exon of the PIEZO1 gene, which is associated with dehydrated hereditary stomatocitosis, an autosomal-dominant syndrome. In addition, we characterized the new GALNS intronic lesion c.245-11C>G causing m-RNA defects, although identified outside the GT/AG splice pair. We estimated the occurrence of the disease in the Italian population to be approximately 1:300,000 live births and defined a molecular testing algorithm designed to help diagnosing MPS IVA and foreseeing disease progression., (© 2014 WILEY PERIODICALS, INC.)

Background: Vascular events in essential thrombocythemia (ET) are associated with advanced age and thrombosis history. Recent information suggests additional effect from the presence of specific mutations., Objectives: To examine the influence of age and thrombosis history on the reported association between mutational status and thrombosis-free survival in ET., Patients and Methods: Analysis was performed using a Mayo Clinic cohort of 300 ET patients, and key findings were reanalyzed by including additional 102 Italian patients., Results: Among 300 Mayo patients with ET (median age 55 yr, 60% females), mutational frequencies were 53% JAK2, 32% CALR, 3% MPL, and 12% JAK2, CALR and MPL wild type. One hundred and six (35%) patients experienced arterial (n = 75) or venous (n = 43) events, before (n = 55) or after (n = 71) diagnosis. In univariate analysis, compared to JAK2-mutated cases, JAK2, CALR and MPL wild type (HR 0.31, 95% CI 0.11-0.86), and CALR-mutated (0.53, 95% CI 0.30-0.92) patients displayed better thrombosis-free survival. JAK2, CALR, and MPL wild type remained significant (P = 0.03; HR 0.32, 95% CI 0.11-0.9) during multivariable analysis that included age (P = 0.01) and thrombosis history (P = 0.0006); a favorable impact from CALR mutations was of borderline significance (P = 0.1; HR 0.62, 95% CI 0.35-1.1), but became significant (P = 0.02) when multivariable analysis including thrombosis history (P = 0.02) was performed on patients younger than 60 yr of age., Conclusions: The favorable impact of mutational status on thrombosis-free survival in ET might be most evident for JAK2, CALR, and MPL wild type patients, whereas the favorable effect from CALR mutations might be confined to young patients., (© 2014 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.)

CALR (calreticulin) trails JAK2 as the second most mutated gene in essential thrombocythemia (ET). Mutant CALR in ET is a result of frameshift mutations, caused by exon 9 deletions or insertions; type-1, 52-bp deletion (p.L367fs*46), and type-2, 5-bp TTGTC insertion (p.K385fs*47) variants constitute more than 80% of these mutations. The current study includes a total of 1027 patients divided into test (n = 402) and validation (n = 625) cohorts. Among the 402 ET patients in the test cohort, 227 (57%) harbored JAK2, 11 (3%) Myeloproliferative leukemia virus oncogene (MPL), and 114 (28%) CALR mutations; 12% were wild-type for all three mutations (i.e., triple-negative). Among the 114 patients with CALR mutations, 51 (45%) displayed type-1 and 44 (39%) type-2 variants; compared to mutant JAK2, both variants were associated with higher platelet and lower hemoglobin and leukocyte counts. However, male sex was associated with only type-1 (P = 0.005) and younger age with type-2 (P = 0.001) variants. Notably, platelet count was significantly higher in type-2 vs. type-1 CALR-mutated patients (P = 0.03) and the particular observation was validated in the validation cohort that included 111 CALR-mutated ET patients (P = 0.002). These findings, coupled with the recent demonstration of preferential expression of mutant and wild-type CALR in megakaryocytes, suggest differential effects of CALR variants on thrombopoiesis., (© 2014 Wiley Periodicals, Inc.)