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Although the prevalence of hereditary hemolytic anemia (HHA) is relatively low in Korea, it has been gradually increasing in recent decades due to increment in the proportions of hemoglobinopathies from immigrants of South East Asia, raising awareness of the disease among clinicians, and advances in diagnostic technology. As such, the red blood cell (RBC) Disorder Working Party (WP), previously called HHA WP, of the Korean Society of Hematology (KSH) developed the Korean Standard Operating Procedures (SOPs) for the diagnosis of HHA in 2007. These SOPs have been continuously revised and updated following advances in diagnostic technology [e.g., flow cytometric osmotic fragility test (FOFT) and eosin-5-maleimide (EMA) binding test], current methods for membrane protein or enzyme analysis [e.g., liquid chromatography-tandem mass spectrometry (LC-MS/MS), ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS), high-performance liquid chromatography (HPLC)], and molecular genetic tests using next-generation sequencing (NGS). However, the diagnosis and treatment of HHA remain challenging as they require considerable experience and understanding of the disease. Therefore, in this new Korean Clinical Practice Guidelines for the Diagnosis of HHA, on behalf of the RBC Disorder WP of KSH, updated guidelines to approach patients suspected of HHA are summarized. NGS is proposed to perform prior to membrane protein or enzyme analysis by LC-MS/MS, UPLC-MS/MS or HPLC techniques due to the availability of gene testing in more laboratories in Korea. We hope that this guideline will be helpful for clinicians in making diagnostic decisions for patients with HHA in Korea.

Background: Reactive thrombocytosis (RT) is a common condition among children, although no studies have examined the etiology or clinical characteristics of RT among Korean children., Methods: This retrospective study evaluated children with RT at a single Korean tertiary center during a 10-year period., Results: RT accounted for 13.5% of children who were admitted to the pediatric ward (4,113/30,355): mild RT, 82.7%; moderate RT, 14.1%; severe RT, 1.1%; and extreme RT, 2.1%. There was a negative correlation between platelet count and Hb level ( P =0.008). There were positive correlations between platelet count and WBC ( P =0.001), erythrocyte sedimentation rate (ESR) ( P =0.007), and admission duration ( P =0.006). The most common cause of RT was infection and the second most common was Kawasaki disease (KD). The highest proportion of lower respiratory tract infection was observed in extreme RT ( P <0.001). The proportion of KD was highest in extreme RT ( P <0.001) and in children aged 1-7.9 years ( P <0.001). The proportion of refractory KD was highest in extreme RT ( P =0.005). In cases of KD, there was a positive correlation between platelet count and fever duration ( P =0.006). Non-KD autoimmune inflammation was only observed in mild/moderate RT, and its proportion was highest in children aged 8-18 years ( P <0.001)., Conclusion: In children, more severe RT was associated with lower Hb, increased WBC, ESR, and prolonged admission. With respiratory infection or KD, extreme RT was associated with more severe disease course., Competing Interests: Authors' Disclosures of Potential Conflicts of Interest: No potential conflicts of interest relevant to this article were reported.

Background: Cytomegalovirus (CMV) causes severe diseases in premature infants and immunocompromised hosts, and antiviral therapy is often required for disease control. However, the clinical manifestations and treatment courses for CMV-associated thrombocytopenia in immunocompetent children are unclear., Methods: Medical records of the children who suffered from thrombocytopenia, and showed positive CMV polymerase chain reaction and CMV-like symptoms were retrospectively analyzed at three university hospitals in Daegu from January 2000 to March 2017. Patients suffering from leukemia, immunodeficiency, and other infections were excluded., Results: Among 1,065 children with thrombocytopenia, 29 (2.7%) displayed CMV-associated thrombocytopenia. The median age at diagnosis was 15 months and the median platelet count was 26,000/µL. They were classified into the CMV-induced thrombocytopenia (23/29) and CMV-related secondary immune thrombocytopenia (ITP, 6/29) groups. Fourteen subjects had hepatic dysfunction, four had Evans syndrome, two had pneumonitis, and one had gastritis. IVIG was used for 21 patients, and six patients among them showed recurrence, for whom IVIG or antiviral therapy was used. All, except one, recurrent or chronic cases belonged to the CMV-induced thrombocytopenia group. Antiviral therapy was used more frequently for the CMV-induced thrombocytopenia group (8/23, 34.8%) than for the CMV-related secondary ITP group (0/6); however, the results were not statistically significant ( P =0.148)., Conclusion: CMV is a rare but unique etiology of thrombocytopenia, and observed even in healthy children after the neonatal period. About one-third patients need antiviral therapy for disease control. Further, CMV-induced thrombocytopenia is more complex than CMV-related secondary ITP., Competing Interests: Authors' Disclosures of Potential Conflicts of Interest: No potential conflicts of interest relevant to this article were reported.

Background: Continuous infusion of factor VIII (FVIII) is a more cost-effective method for treating hemophilia A than intermittent bolus injection. However, there is currently no specific data in Korea about the progress of in vitro FVIII coagulant activity (FVIII:C) after reconstitution from its lyophilized form., Methods: Three commercial FVIII concentrate products (two recombinant FVIII and one plasma-derived) were used. In vitro FVIII:C was measured at 0, 2, 4, 6, and 8 hours following reconstitution in both the indoor light-exposed and light-shielded groups., Results: For the three drugs, in vitro FVIII:C decreased over the 8 hours following reconstitution (P<0.001). The decline of FVIII:C was linear (P<0.001). In vitro FVIII:C for the indoor light-exposed groups was 95.3±1.9% and 90.6±2.5% after 4 and 8 hours following reconstitution, respectively, compared to baseline activity. In the light-shielded group, FVIII:C was 95.4±1.1% and 90.9±1.7% of the baseline activity after 4 and 8 hours, respectively. There was no statistical difference between FVIII:C in the indoor light-exposed and light-shielded groups (P=0.849)., Conclusion: In vitro FVIII:C decreased after reconstitution, but activity was maintained at over 90% of the baseline value during 8 hours. Exposure to indoor light did not accelerate the loss of FVIII:C over the experimental time. This result indicates that CI with FVIII is available in 8-hour intervals, with no indoor light-exposure precautions needed.

Background: The immune thrombocytopenia (ITP) criteria were newly standardized by the International Working Group. Thus, we analyzed the natural course of childhood chronic ITP to predict the prognosis based on the revised criteria., Methods: The medical records of children with chronic ITP from May 2000 to February 2013 in our institute were reviewed., Results: Forty-seven children with chronic ITP who were not undergoing corticosteroid therapy were included. Their initial platelet count was 23±25×10(9)/L, and age at diagnosis was 6.3±4.1 years. The follow-up period was 5.4±3.7 years. Among them, 44.7% (21/47) showed spontaneous remission and maintained a platelet count ≥100×10(9)/L. And 66.0% (31/47) maintained a platelet count ≥50×10(9)/L until the last follow-up date. The time periods required for the platelet count to be maintained ≥50×10(9)/L and ≥100 ×10(9)/L were 3.1±2.7 and 3.6±2.7 years. Age at diagnosis in the ≥50×10(9)/L group (5.7±4.4 years) was significantly lower than the age at diagnosis in the <50×10(9)/L group (7.4±3.3 years) (P=0.040). And follow-up period was the factor influencing prognosis between the ≥100×10(9)/L group and <50×10(9)/L group (P=0.022)., Conclusion: Approximately 45% of children with chronic ITP recovered spontaneously about 3-4 years after the diagnosis and 2/3 of patients maintained a platelet count ≥50×10(9)/L, relatively safe state. Age at diagnosis of ITP and follow-up period were the factors influencing prognosis in this study.