Immunodeficiency-74 (IMD74) is an X-linked recessive specific immunologic disorder characterized by the development of severe respiratory insufficiency in response to infection with the COVID-19 coronavirus, also known as SARS-CoV-2 ssRNA coronavirus. Affected individuals usually require mechanical ventilation in the ICU in order to survive. Laboratory studies show activation of the immune response and may show perturbation of some values, such as increased D-dimers and fibrinogen. In vitro functional studies of patient immune cells show impaired signaling through the TLR7 pathway, resulting in defective type I and type II interferon (IFN) responses. The patients reported to date did not have a history of immunodeficiency or chronic disease (summary by van Der Made et al., 2020).