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.

Table 2 Factors that increase the rate of autoimmunity in coronavirus disease 2019

The ability of the virus to infect nearly all the human body tissues

Large RNA with interrupted transcription increases the pool of epitopes with increased chances of molecular mimicry and interaction with the host immune system

The overlap between some viral and human peptides

The viral-induced tissue damage increases the chance of deviated immune system

The immunogenic effect of the robust and complex binding between sACE-2 and SARS-CoV-2 S protein

SARS-CoV-2: Severe acute respiratory syndrome coronavirus 2.

Table 3 Differences between the classic Kawasaki disease and Kawasaki disease - coronavirus disease 2019

	Classic KD	KD-COVID-19
Age	Children < 5 yr of age	Older age
General condition	Less ill than in KD-COVID-19	More severely ill
Gastrointestinal & meningeal signs	Less common	More common
CBC	Leucocytosis, anemia, & thrombocytosis. Thrombocytopenia may occur	Leukopenia with marked lymphopenia, thrombocytopenia
Ferritin	Increased	Markedly increased
Incidence of myocarditis	Subclinical myocarditis is nearly present in all patients. However, clinically evident myocarditis is uncommon.	Very high, up to 60.4% in patients with KD-like multisystemic disease.
Response to IV gamma globulins	Well-responding	Resistance to IVIG therapy is common.
Adjunct steroids	May be needed	Usually needed

COVID-19: Coronavirus disease 2019; CBC: blood cell count; KD: Kawasaki disease; IVIG: Intravenous immunoglobulin.

Table 4 Factors that affect the severity of coronavirus disease 2019 in patients with autoimmune diseases

The age and sex of the patients

The type of the autoimmune disease

The severity of the autoimmune disease.

Presence of comorbidities

The type of medication used

Disruption of the medical care continuity

Lack of medication adherence

Other factors that increase COVID-19 severity in the general population

COVID-19: Coronavirus disease 2019.