COVID-19 disease and autoimmune disorders: A mutual pathway

Table 1 Factors affecting the severity of coronavirus disease 2019 infections

Factor		Example
Viral-related factors		The viral load[24]; Mutation/virulence; Previous infections with other Coronaviruses e.g., SARS-CoV[43,59]
Host-related factors:	Demographic factors	Patients' age[61,62]
		Gender[80,182]
		Race/ethnic group
	Physiological	Pregnancy[215]; Personel differences in ACE2 receptors distribution[13]
	Pathological factors	Presence of comorbidities such as obesity, hypertension, tuberculosis, HIV, anemia, nutritional deficiencies, or diabetes mellitus[13,45,159,169,171,181]
	Immunological factors	The type of HLA-antigen[20-23]
		The plasma numbers of B cells, T cells, and natural killer lymphocytes[40,41]
		The hemoglobin and ferritin levels[216]
		The levels of C3 and C4[38]
		The differences in the MBL protein[28]
	Environmental factors	Socioeconomic status[217]
		Overcrowding[218]
		Smocking[205]
		Alcohol consumption[204]
		Particular occupations: Occupations that involve a higher degree of physical proximity to others over long periods[219]
	Pharmacological factors	Certain drugs increase the severity (e.g., rituximab, high-dose corticosteroid)[140,187,191]. Certain drugs decrease the severity (e.g., ubiquinone, ezetimibe, flecainide, rosuvastatin, artificial tears, licorice)[214]
		Vaccination status of the patients

ACE2: Angiotensin-converting enzyme II; HLA: Human leukocyte antigens; HIV: Human immunodeficiency virus; MBL: Mannose-binding lectin; SARS-CoV: Severe acute respiratory syndrome coronavirus 2.