MYH9 -related disease ( MYH9 -RD) is an autosomal dominant thrombocytopenia with giant platelets variably associated with young-adult onset of progressive sensorineural hearing loss, presenile ...cataract, and renal damage. MYH9 -RD is caused by mutations of MYH9 , the gene encoding for non-muscle heavy-chain myosin-9. Wild-type and mutant myosin-9 aggregate as cytoplasmic inclusions in patients’ leukocytes, the identification of which by immunofluorescence has been proposed as a suitable tool for the diagnosis of MYH9 -RD. Since the predictive value of this assay, in terms of sensitivity and specificity, is unknown, we investigated 118 consecutive unrelated patients with a clinical presentation strongly consistent with MYH9 -RD. All patients prospectively underwent both the immunofluorescence assay for myosin-9 aggregate detection and molecular genetic analysis of the MYH9 gene. Myosin-9 aggregates were identified in 82 patients, 80 of which (98%) had also a MYH9 mutation. In the remaining 36 patients neither myosin-9 aggregates nor MYH9 mutations were found. Sensitivity and specificity of the immunofluorescence assay was evaluated to be 100% and 95%, respectively. Except for the presence of aggregates, we did not find any other significant difference between patients with or without aggregates, demonstrating that the myosin-9 inclusions in neutrophils are a pathognomonic sign of the disease. However, the identification of the specific MYH9 mutation is still of importance for prognostic aspects of MYH9 -RD.
In Italy, a significant proportion of patients with autosomal dominant inheritance of macrothrombocytopenia have been recognized as having heterozygous Bernard-Soulier syndrome carrying the ...Bolzano-type defect. This condition prompted a systematic review of our out-patients with chronic isolated macrothrombocytopenia. We recognized that the affected members of two unrelated families represented a new variant of heterozygous Bernard-Soulier Syndrome with autosomal dominant inheritance. Sequencing analysis of the GPIbα gene revealed a novel heterozygous mutation, A169C, resulting in an N41H substitution in the protein. This aminoacid belongs to the first leucine-rich repeat of the chain. The molecular modeling suggests that the replacement of the N41 with a histidine (N41H) drastically disturbs the structure of the first portion of GPIbα N-terminal, directly involved in von Willebrand factor binding. As a consequence, platelet aggregation to 1.2 mg/mL of ristocetin is slightly impaired and flow cytometry reveals a reduced binding of monoclonals directed against N-terminal epitopes of the GPIbα.
Platelet glycoprotein GPIbα mutations are the basic defect behind Bernard-Soulier syndrome, a rare inherited macrothrombocytopenia characterized by anomalies of the GPIbα, GPIbβ and GPIX subunits of ...von Willebrand factor receptor. A 32-year old man was investigated for suspected Bernard-Soulier syndrome. Ristocetin induced agglutination was absent. Flow cytometry and Western blot analysis showed a severe reduction in GPIbα, but sequencing revealed only a biallelic c.386A>G substitution, theoretically leading to a p.Asn110Glu variation. To further clarify the data, megakaryocyte cultures were set. Though the maturation of megakaryocytes was normal, proplatelet formation was defective and GPIbα mRNA was not detectable. GPIX protein was slightly reduced and GPIbβ polypeptide almost absent. Computational analysis showed that the c.386A>G mutation disrupted an exon splicing enhancer motif involved in the proper maturation of the GPIbα transcript. The c.386A>G mutation suggests a unique mutational mechanism causing the virtual absence of GPIbα without creating a stop codon.
There were 50 consecutive idiopathic thrombocytopenic purpura (ITP) adult patients (platelet count < 100 × 109/L) grouped according to positivity or negativity of a solid-phase modified antigen ...capture enzyme-linked immunosorbent assay (ELISA) test (MACE) against glycoprotein IIb/IIIa (GPIIb/IIIa), Ib/IX, and IIa/IIIa. Observation started on the day of MACE assay and lasted at least 6 months. Clinical worsening was defined as the need for starting or modifying therapy because of thrombocytopenia lower than 20 × 109/L or patient admission due to bleeding symptoms. MACE-positive patients had a higher probability of clinical worsening than MACE-negatives (P < .004). The proportion of patients worsening was 18 (72%) of 25 among MACE-positives and 8 (32%) of 25 among MACE-negatives. The median time to clinical worsening was 2.1 months for MACE-positive patients and 27.7 months for MACE-negatives. The assay of specific platelet autoantibodies may be a useful prognostic tool for the clinical course of ITP. (Blood. 2004;103:4562-4564)
Background:
JAK2V617F mutation occurs in 90% of polycythemia vera (PV) and in 50% of essential thrombocythemia (ET) patients.
Materials and methods:
253 consecutive patients affected by ...myeloproliferative disorders (MPD, 121 PV, 132 ET) were evaluated and stratified in 4 age groups: 18–39, 40–59, 60–75 and over 75 years (>75). The JAK2V617F mutation was searched and its allele burden was evaluated.
Results:
The percentage of mutated patients increased progressively with age mainly in patients >75 (p=0.0015 vs 18–39, p=0.0021 vs 40–59 and p=0.012 vs 60–75). We also found a progressive increase in allele burden with age (R
2
=0.042). Thrombotic events were more common in patients carrying the mutation in comparison with wild type (WT) (p=0.006, coefficient risk 1.94). No differences in the percentage of patients carrying the JAK2V617F mutation were found, in spite of different follow-up durations (<5 yrs, 5–10 yrs, 10–15 yrs, >15 yrs). The JAK2V617F allele burden was similar in patients with (57±31%) and without (45±26%) long-term hydroxyurea treatment.
Conclusions:
JAK2V617F mutation is more common in old than in young patients with MPD. Older patients have an higher allele burden.
The relationship between thrombopoietin (TPO) and its receptor cMpl in thrombocytopenic conditions has not been entirely clarified. To elucidate this interplay may expand the spectrum of indications ...of TPO mimetics. In this study we have explored the relationship between TPO and cMpl in platelets and megakaryocytes of 43 patients with thrombocytopenia due to idiopathic thrombocytopenic purpura (ITP), bone marrow hypoplasia, myelodysplastic syndromes (MDS), and familial thrombocytopenia. Data were compared to cMpl and TPO in patients with a normal platelet count and in patients with thrombocytosis due to essential thrombocythemia (ET). All but familial patients showed higher TPO compared to controls. All thrombocytopenic states were invariably associated with increased expression of platelet cMPL compared to healthy controls. ET patients showed normal TPO and a trend toward a reduced cMpl expression. Immunofluorescence of bone marrow sections from patients with ITP and MDS failed to show a peculiar pattern compared to controls. Multiple mechanisms regulate TPO and cMpl in thrombocytopenic conditions.
Abstract MYH9 -related disease ( MYH9 -RD) is a rare autosomal dominant disorder caused by mutations in MYH9 , the gene encoding the heavy chain of non-muscle myosin IIA. Patients present with ...congenital macrothrombocytopenia and inclusion bodies in neutrophils and might develop sensorineural deafness, presenile cataract, and/or progressive nephropathy leading to end-stage renal failure. In two families with macrothrombocytopenia we identified a novel c.3485G > C mutation in the last nucleotide of exon 25. Bioinformatic tools for splice site prediction and minigene functional test predicted splicing anomalies of exon 25. However, analysis of RNA purified from patient’s peripheral blood did not allowed us to detect any anomalies, suggesting that RNA processing is correct at least in this tissue. Therefore, we concluded that c.3485G > C leads to a novel missense mutation (p.Arg1162Thr) of myosin-9, which resulted to be slightly degraded in patient platelets. A precise definition of the effect of mutations is fundamental to improve our knowledge into the pathogenetic mechanisms responsible for the disease.
Hydroxyurea (HU) is effective in controlling thrombocytosis while reducing the risk of thrombosis in essential thrombocythemia (ET), polycythemia vera (PV) and myelofibrosis (MF). However, HU may ...carry more or less severe side-effects. Rare cases of patients with painful leg ulcers have been published. We report our experience on such a side-effect in a large cohort of patients with ET and PV treated with HU and review the literature on the topic. Five (4%) out of our 124 patients (69 ET, 51 PV, 4 MF; 49 males, 75 females; mean age at diagnosis 59.1+/-11.8 years) treated with HU developed painful leg ulcers. Sixty-one other patients affected with Phmyeloproliferative disorders (Ph- MPD) developing HU-related painful leg ulcers are described in the English literature. All our five patients were women and developed leg ulcers over the age of 75. Sixty-five percent of all described cases are women; 59% were over 65 years of age and 45% over 70. Most cases received over 1 gr HU per day for at least 1 year. The pathogenesis of HU-induced skin ulcers remains elusive. Treatment is difficult and requires prompt cessation of HU therapy.
Background and aims:
A previous thrombotic event and advanced age are well-known risk factors for thrombosis in essential thrombocythemia (ET). In these patients, therefore, cytotoxic drugs are ...needed to reduce platelet count. In spite of this convincing idea, in clinical practice, some old patients do not use platelet-reducing drugs, for a variety of causes, and few specific studies in old patients with ET are available. Our retrospective study reports single-center experience in 54 old ET patients with long follow-ups.
Methods:
We compared the clinical outcome of 27 ET old patients not taking cytotoxic drugs (group A) with 27 cases treated with hydroxyurea (HU) (group B), evaluating the incidence of thrombosis and thrombosis-free survival. In 16 patients in group A and in 18 in group B, V617FJak2 mutation was sought. About 20% of HU-treated patients developed major side-effects.
Results:
No significant difference was found in the occurred thrombosis between the 2 groups in either clinical or laboratory features. V617FJak2 was equally common in groups A and B, and in patients with or without thrombosis.
Conclusions:
This study is not randomised and includes a small number of patients. However, it shows that it is necessary to identify better patients who really need treatment, as the side-effects of HU are relatively common in old people and their treatment should be discontinued. V617FJak2 does not define the thrombotic risk in old ET patients.
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