CRISPR/Cas9 is a versatile genome-editing technology that is widely used for studying the functionality of genetic elements, creating genetically modified organisms as well as preclinical research of genetic disorders. However, the high frequency of off-target activity (≥50%)—RGEN (RNA-guided endonuclease)-induced mutations at sites other than the intended on-target site—is one major concern, especially for therapeutic and clinical applications. Here, we review the basic mechanisms underlying off-target cutting in the CRISPR/Cas9 system, methods for detecting off-target mutations, and strategies for minimizing off-target cleavage. The improvement off-target specificity in the CRISPR/Cas9 system will provide solid genotype–phenotype correlations, and thus enable faithful interpretation of genome-editing data, which will certainly facilitate the basic and clinical application of this technology.

While COVID-19 typically manifests with respiratory symptoms, mounting evidence suggests that it may precipitate a hyperinflammatory state that makes patients susceptible to autoimmune complications. Some known autoimmune complications of COVID-19 include antiphospholipid syndrome, (1) autoimmune thrombocytopenia, (2) autoimmune haemolytic anaemia (3) and Guillain-Barré syndrome. (4) We herein describe a patient with COVID-19 who developed Hashimoto's thyroiditis.A 45-year-old Chinese man who lived in a dormitory with a COVID-19 outbreak presented with non-productive cough and rhinorrhoea for one day. On the second day of his symptoms, he was diagnosed with COVID-19 through a SARS-CoV-2 (severe acute respiratory syndrome coronavirus 2) reverse transcriptase-polymerase chain reaction test from a nasopharyngeal swab and admitted to a COVID-19 isolation ward. Seven days after the onset of a mild COVID-19 upper respiratory tract infection, he reported complete resolution of his respiratory symptoms but complained of acute-onset severe generalised fatigue and muscle weakness. He had no neck pain, constipation or weight gain. Before the symptoms began, he had been in good health and working full-time, and had not been taking any supplements or chronic medications. He had never smoked and was teetotal. He also denied any personal or family history of autoimmune or thyroid disease.On examination, the patient was afebrile and haemodynamically stable with no bradycardia or hypothermia. Cardiac, respiratory, abdominal and neurological examinations were unremarkable. The patient was clinically euthyroid with no goitre. Investigations were performed to determine the cause of his acute lethargy. His thyroid function test (TFT) showed an elevated thyroid-stimulating hormone (TSH) reading of 6.49 μIU/mL and a low free thyroxine (fT4) level of 9.19 pmol/L, which is typical of primary hypothyroidism. His thyroid peroxidase antibody levels exceeded the upper limit of detection (> 2,000 IU/mL), which was indicative of Hashimoto's thyroiditis. There was no anaemia, and electrolyte levels were normal. Inflammatory markers and creatinine kinase levels were not elevated, and the chest radiograph showed no consolidation or effusion. The patient was started on oral levothyroxine 25 mcg once a day and was counselled about his diagnosis of Hashimoto's thyroiditis. Five weeks later, the patient reported that he felt energised and had started running regularly. His TFT was still deranged but had improved (fT4 10.91 pmol/L, TSH 6.59 μIU/mL).To the best of our knowledge, this is the first case of a patient who developed Hashimoto's thyroiditis after a COVID-19 infection. The time interval from the onset of his first respiratory symptoms to the inception of Hashimoto's thyroiditis was similar to that of reported cases of other autoimmune complications (1)(2)(3)(4) and corresponds to the time frame of the cytokine storm. (5) It indicates that the hyperinflammatory state triggered by COVID-19 may predispose patients to develop autoimmune com...

Objective: Migrant workers, a marginalized and under-resourced population, are vulnerable to coronavirus disease 2019 (COVID-19) due to limited healthcare access. Moreover, metabolic diseases—such as diabetes mellitus (DM), hypertension, and hyperlipidemia—predispose to severe complications and mortality from COVID-19. We investigate the prevalence and consequences of undiagnosed metabolic illnesses, particularly DM and pre-diabetes, in international migrant workers with COVID-19. Methods: In this retrospective analysis, we analyzed the medical records of international migrant workers with laboratory-confirmed COVID-19 hospitalized at a tertiary hospital in Singapore from April 21 to June 1, 2020. We determined the prevalence of DM and pre-diabetes, and analyzed the risk of developing complications, such as pneumonia and electrolyte abnormalities, based on age and diagnosis of DM, and pre-diabetes. Results: Two hundred and fouty male migrant workers, with mean age of 44.2 years [standard deviation (SD), 8.5years], were included. Twenty one patients (8.8%) were diagnosed with pre-diabetes, and 19 (7.9%) with DM. DM was poorly controlled with a mean HbA1c of 9.9% (SD, 2.4%). 73.7% of the patients with DM and all the patients with pre-diabetes were previously undiagnosed. Pre-diabetes was associated with higher risk of pneumonia [odds ratio (OR), 10.8, 95% confidence interval (CI), 3.65–32.1; P < 0.0001], hyponatremia (OR, 8.83; 95% CI, 1.17–66.6; P = 0.0342), and hypokalemia (OR, 4.58; 95% CI, 1.52–13.82; P = 0.0069). Moreover, patients with DM or pre-diabetes developed COVID-19 infection with lower viral RNA levels. Conclusions: The high prevalence of undiagnosed pre-diabetes among international migrant workers increases their risk of pneumonia and electrolyte abnormalities from COVID-19.

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