- A severe inflammatory response that presents as a fever, nausea, and swelling
- Has been observed in tandem with COVID-19 pulmonary symptoms
- Involves overproduction of cytokines (key proteins in the immune system)
- Immunosuppression can be helpful in calming the immune system and mitigating this extreme immune response

Secondary Haemophagocytic Lymphiohistocytosis and COVID-19

- Common Variable Immunodeficiency (CVID) is a disorder which lowers the immune systems defenses and makes patients more susceptible to infections in the lungs, sinuses, and ears
- A 53 y/o patient with CVID was admitted with COVID-19
- Patient was already receiving intravenous immunoglobulin (IVIG) for their CVID
- Levels of patient’s immunoglobulin were taken upon arrival and it was noted that their IgG was normal, but IgM and IgA were low and undetectable respectively
- Patient received additional IVIG daily as well as supplemental oxygen in the form of a nasal cannula and then intubation
- Patient was extubated after 3 days and eventually weaned back to room air as well as discharged on day 14 due to clinical improvement
- The paper also noted that there were 2 similar cases of CVID patients receiving supplemental IVIG in Italy who also made a similar recovery
- It was also stated that while testing was not performed for cytokine storm syndrome, 53 y/o did develop some acute respiratory distress syndrome during their treatment

Common Variable Immunodeficiency 

An inflammatory storm may result from pathogenic T cells and inflammatory monocytes with high levels of IL-6 secretion entering pulmonary circulation in large quantities. This occurrence can also cause an immune disorder in COVID-19 patients with severe complications.  

Figure illustrating how pathogenic T cells and inflammatory monocytes enter pulmonary circulation and incite an inflammatory storm and immune disorder 

- SARS-CoV-2 infection associated with hepatitis in an infant with X-linked severe combined immunodeficiency

Severe Combined Immunodeficiency

Immunological diseases are high-risk comorbid conditions that put patients at greater risk for severe COVID-19 infections and negative health outcomes. These comorbidities, which include common variable immunodeficiency, severe combined immunodeficiency, and secondary haemophagocytic lymphohistiocytosis, can significantly impair the body's immune defenses or trigger extreme, uncontrolled inflammatory responses such as cytokine storms when responding to a SARS-CoV-2 infection.

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COVID-19 comorbidities are high risk conditions that put patients at greater risk for infection and negative outcomes. Some COVID-19 comorbidities have been found to be: 
- Cancer 
- Cardiovascular Disease
- Diabetes
- Digestive Diseases
- HIV
- Hypertension
- Immunological Disease
- Liver Injury
- Obesity
- Renal disease
- Respiratory System Disease

COVID-19 Patient Comorbidities

COVID-19 may be worse in patients with comorbidities, and this can cause damage to the heart, liver, kidneys, and blood and immune systems. Many patients have had multiple organ failure that started with pneumonia, and became worse when therapeutic effects were unsatisfactory. Comorbidities can cause a patient's deterioration, leading to multiple organ failure. Organ function should be closely monitored and protective measures such as mechanical ventilation, glucocorticoids, antivirals, symptomatic treatments, and anti-shock therapy should be administered if necessary. 

Multiple Organ Injuries in COVID- 19 Patients with Comorbidities

- Hypertension and COVID-19 by Geographic Location
- Hypertension and COVID-19 by Topic

Hypertension as a Comorbidity of COVID-19

- Respiratory System Disease in COVID-19 Patients by Geographic Location 
- Asthma as a Comorbidity of COVID-19

Respiratory System Disease as a Comorbidity of COVID-19

Human Immunodeficiency Virus (HIV) and COVID-19 can interact synergistically as a syndemic. While HIV itself may not directly increase the risk of contracting SARS-CoV-2, people living with HIV frequently have other pre-existing conditions—such as diabetes, hypertension, and cardiovascular diseases—that heighten the severity and lethality of a COVID-19 coinfection.

HIV as a Comorbidity of COVID-19

- By country
- Liver Transplantation
- Chronic Liver Disease

Liver Injuries as a Comorbidity of COVID-19 

- This node acts as a general summary of the comorbidity of cancer and COVID-19 from a paper that analyzed many other papers detailing the same thing at its time of release.
- Via a pooled meta-analysis of studies from around the globe analyzing the prevalence of cancer in COVID-19 patients, it was found that the prevalence of cancer in COVID-19 patients is about 2%, which is higher than the overall prevalence of cancer in the population (I think).
- This leads to a hypothesized conclusion that while there is not a lot of data for COVID-19 infection and cancer patients, there is an elevated risk for these patients. However, due to inconclusive and generally lacking data on this topic, this conclusion is not concrete.
- Many major cancer centers worldwide have taken extra precaution when it comes to the treatment of these patients as many cancer treatments (e.g., chemotherapy) weaken the immune system as a side effect.
- There has currently been no order to withhold chemotherapy, radiotherapy, immunotherapy, or delaying adjuvant therapy to treat cancer patients, however extra care must be taken by patients and physicians alike to not allow these high-risk patients to become infected.

Cancer as a Comorbidity of COVID-19 

Patients with digestive diseases like inflammatory bowel disease (IBD) or gastrointestinal cancer are at a higher risk to experience more severe symptoms of COVID-19. Autopsy studies are important in understanding how COVID-19 affects the digestive system. More data needs to be collected to determine the exact relationship between digestive diseases and COVID-19. 

Digestive Diseases as a Comorbidity of COVID-19

- Prevalence of pathophysiology, prognosis, and practical considerations
- Knowledge in progress
- The link between diabetes and ACE2
- Diabetes in COVID-19 patients by geographic location 
- Degree of Hyperglycemia on COVID-19 mortality
- Diabetes Medication on COVID-19 mortality
- COVID-19 and endocrine diseases. A statement from the European Society of Endocrinology

Diabetes as a Comorbidity of COVID-19

During the COVID-19 pandemic, the routine treatment of and communication regarding pre-existing patient comorbidities were significantly disrupted. To ensure continuity of care, healthcare providers implemented new clinical guidelines and safety precautions, largely utilizing telehealth and virtual communication platforms. While these new communication and treatment policies share broad similarities across medical fields, specific protocols vary based on the unique management needs of each comorbidity.

Changes to COVID-19 Patient Comorbidity Treatment and Communication

Cardiovascular disease is a risk factor for severe COVID-19, and COVID-19 causes cardiovascular complications. 

Cardiovascular Disease and COVID-19

- A retrospective multi-center experience of renal transplants from India during COVID-19 pandemic

Renal Diseases as a Comorbidity of COVID-19

Immunological Diseases as a Comorbidity of COVID-19

This node categorizes references and research papers related to COVID-19 patient comorbidities by their publishing journal.

COVID-19 Comorbidities References by Journal

Obesity is a significant comorbidity for COVID-19, affecting the severity of symptoms, length of hospital stays, and overall clinical outcomes. In obese patients, a higher baseline level of proinflammatory cytokines increases the risk of experiencing a severe cytokine storm. The clinical impact of this comorbidity also varies depending on factors such as geographic location and patient age.

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