Discussion
In the epidemiological study from China, ninety per cent of the SARS-CoV-2 infected children had mild to moderate symptoms.3 Younger children, less than 5-year-old, were more likely to develop a complication.3 Majority of symptomatic children with COVID-19 presented with upper respiratory symptomatology.1 There was a lack of data on COVID-19 infection in immunocompromised children. However, the outcome can be predicted based on the effect of other Human Coronavirus (HCoV) infection to immunocompromised children. In a retrospective study, both of the immunocompromised and immunocompetent children with HCoV infection presented similarly, mainly with fever, cough and sore throat.4 The severity was identical even with different strains of HCoV.1,4 However, immunocompromised children were more likely to develop severe pneumonia compared to immunocompetent children.4
Morbidity and mortality in the patients with COVID-19 are thought to be due to hyper-inflammatory state such as cytokine storm syndrome.5 It is thought that immature and poor functioning ACE-2 receptor which reduced the SARS-CoV-2 virus affinity to the receptor, higher level of antibody against respiratory viruses, the cross protection of childhood immunisation program, and the lack of coronavirus-specific memory cells have led to reduce direct cell-mediated attack and inflammation on alveoli and other organs.3,6 This exaggerated innate immune response was not seen in the immunocompromised children.2,7 During the SARS-CoV outbreak in 2002/2003, children with organ transplant had good outcome.7 Similarly, there was no documented severe COVID-19 pneumonia among paediatric liver transplant patients in Italy.7
In contrast to the reported case of COVID-19 positive leukemic child by Chen et al., our patient was asymptomatic throughout the disease course. The reported child developed a high-grade fever which progressed into pneumonia requiring intensive care unit admission.8The severe neutropenia and concomitant influenza A infection might have contributed to more severe disease in the reported child.8
In conclusion, this report and other previous cases of COVID-19 in immunocompromised children revealed that the infection is mild. The severity may however be worse with concomitant other respiratory virus infection. Further evidence on the pathogenesis and outcome of SARS-CoV-2 infection on immunocompromised children are required before any conclusion can be made.