Methemoglobinemia is a rare disorder associated with oxidization of divalent ferroiron of hemoglobin (Hb) to ferri-iron of methemoglobin (MetHb). Methemoglobinemia can result from either inherited or acquired processes. Acquired forms are the most common, mainly due to the exposure to substances that cause oxidation of the Hb both directly or indirectly. Inherited forms are due either to autosomal recessive

Faced with the rapidly evolving COVID-19 pandemic, in March 2020 the UK Government advocated strict self-isolation ('shielding') to protect extremely vulnerable patient groups deemed at high risk of severe SARS-CoV-2 infection. 1 These included children and adults with sickle cell anemia (HbSS). On the advice of the National Hemoglobinopathy Panel (NHP), a multidisciplinary expert advisory group, shielding guidance was extended to all sickle cell disease (SCD) sub-types. Patients with transfusion dependent (TDT) and non-transfusion dependent thalassemia (NTDT), Diamond-Blackfan anemia (DBA) and other rare inherited anemias were also advised to shield if considered at high risk based on agreed clinical criteria. These included severe iron overload, splenectomy, diabetes and cardiac disease. 2 Data provided by two participating centers with the largest thalassemia cohorts indicate up to 30% of patients meet these criteria. In order to evaluate the impact of these measures and inform guidance on the clinical management of COVID-19 and public health policy, a real-time survey of confirmed and suspected cases of COVID-19 in hemoglobinopathy and rare inherited anemia patients was initiated on behalf of the NHP and National Health Service (NHS) England Clinical Reference Group for Hemoglobinopathies. Data were submitted weekly by the 14 Hemoglobinopathy Coordinating Centers (HCC) in England, providing national coverage. HCC were encouraged to follow World Health Organization (WHO) case definitions which include both confirmed and clinically suspected COVID-19. 3 Anonymised data were collected using a standardised report template (see the Online Supplementary Data) and presented weekly to the NHP. Between April 8 and May 6, 2020, a total of 195 confirmed or suspected COVID-19 cases (male: 87; female: 108) were reported. The timeline of case accrual is shown in Figure 1A. The median age was 33 years (range: 6 weeks to 92 years). The distribution according to age and sex is shown in Figure 1B. PCR for SARS-CoV-2 RNA was positive in 99 of 157 (63%) cases tested (Figure 2A). Laboratory confirmation was not available for 34 (17.4%) cases, 31 of which were managed in the community for suspected COVID-19 before widespread testing became available. SCD accounted for 166 (85.1%) of cases reported, with 129 (77.7%) severe (HbSS or HbSβ 0-thalassemia) and 37 (22.3%) mild (HbSC, HbSβ +-thalassemia or HbSE) genotypes (Figures 2A-B). There were 149 adults and 17 children (defined as ≤18 years). Ninety-five (57%) were female. One hundred and twenty-eight (77.1%) SCD patients were admitted to hospital of whom 15 (11.7%), all adults, required non-invasive and/or mechanical ventilation (Figure 2B). The proportion of patients who required critical care was higher in mild genotypes, 8 of 29 (27.6%), than severe genotypes, 7 of 99 (7.1%) (Figure 2B). Sixty of 154 (39%) patients for whom data were available received transfusion (red cell exchange 46 [29%]; simple [top-up] transfusion 15 [10%]) during the COVID-19 episode. The proportion of tr...