Individuals with Down syndrome, the nation’s most common genetic disorder, represent a small, vulnerable segment of the U.S. population whose comorbid conditions may make them particularly susceptible to severe forms of COVID-19.

In fact, people with Down syndrome who are over the age of 30 appear to be about nine times as likely as the general population to be hospitalized for COVID-19, and their hospital stays tend to be more than twice as long, with a median of 17 days, according to a recent study from the Icahn School of Medicine at Mount Sinai that was uploaded onto the pre-print server medRxiv. Approximately 250,000 people in the United States have Down syndrome.

“When you don’t have a critical mass of people who are able to advocate for themselves, which is the case with Down syndrome, then people start falling through the cracks,” says the study’s senior author, Dusan Bogunovic, PhD, Associate Professor of Microbiology, and Pediatrics, and Director of the Center for Inborn Errors of Immunity, which is part of the Mindich Child Health and Development Institute. “We did not want that to happen. We felt that particular attention should be paid to the prevention and treatment of COVID-19 in individuals with Down syndrome.”

From left: Dusan Bogunovic, PhD, and Louise Malle, MD/PhD candidate

Dr. Bogunovic and MD/PhD candidate Louise Malle led a research team that examined the electronic medical records of 4,615 patients with COVID-19 who were hospitalized within the Mount Sinai Health System. They expected to find one or perhaps even two patients with Down syndrome based on the syndrome’s low prevalence within the population. Instead, they identified six adults, all of whom were in their 50s except for one, who was in her 30s. Two of the six patients, both in their 50s, succumbed to the disease. By comparison, Dr. Bogunovic says, 2 out of 30 cases were fatal in an age, sex, and race-matched control group of people who did not have Down syndrome.

Four of the six Down syndrome patients with COVID-19 were also diagnosed with sepsis, which is a marker of extreme inflammation, according to Ms. Malle. The individuals with Down syndrome were more likely to be hospitalized in an intensive care unit and to have been placed on a ventilator. In addition, she says, a constellation of other health issues associated with Down syndrome, such as autoimmune disease, epilepsy, and dementia, may have played a role in the severity of COVID-19. Further studies will be needed to determine whether these patients were more likely to produce higher levels of inflammatory markers.

Over the past 20 years, improved health care for individuals with Down syndrome has led to increased longevity, with many now living into their early 60s. That however, is still roughly 20 years shorter than individuals without the disorder. The median age of the hospitalized patients with Down syndrome was 54, roughly 12 years younger than the rest of the population that was hospitalized as a result of the disease.

Dr. Bogunovic says one positive finding was that “none of the patients we looked at were pediatric patients, so it does follow the trend of the general population that the older you are the more likely you are to be hospitalized with COVID-19.” He adds that the current study points to the need for “additional research into the medical conditions of marginalized patients with rare genetic conditions,” particularly during a pandemic.

Members of the Pathology Department’s autopsy study, from left: Elisabet Pujadas, MD, PhD; Zachary Grimes, DO; Kenneth Haines, MD; Clare Bryce, MBChB; Mary Fowkes, MD, PhD; and Carlos Cordon-Cardo, MD, PhD.

Since March 8, when Mount Sinai West hospitalized its first patient with COVID-19, more than 8,000 individuals with the disease have been admitted to the Mount Sinai Health System. During that time, the medical community’s knowledge of COVID-19 has evolved from seeing it as a respiratory illness to understanding its effect on the blood vessels and multiple organs.

“Mount Sinai has been the epicenter of the epicenter,” says Dennis S. Charney, MD, Anne and Joel Ehrenkranz Dean, Icahn School of Medicine at Mount Sinai, and President for Academic Affairs, Mount Sinai Health System. “We’ve been attacking COVID-19 from many different perspectives and we’ve made a lot of progress in a short amount of time.”

Indeed, as Mount Sinai’s front-line doctors, nurses, and others faced a tsunami of sick patients entering their hospitals, they were able to improve patient outcomes by working closely with their colleagues in other specialties and in laboratories at the Icahn School of Medicine at Mount Sinai. Through careful observations and investigations they have come to define COVID-19 as a new disease that attacks the endothelial cells that line the body’s blood vessels. How the disease plays out in each individual depends largely on the state of their immune system and whether they have co-morbidities, such as obesity, hypertension, or heart disease, which affect blood flow within the body. Approximately 80 percent of people with COVID-19 are able to recover without hospitalization.

“This is a disease we had not seen before,” says Carlos Cordon-Cardo, MD, PhD, the Irene Heinz Given and John LaPorte Given Professor and Chair of the Lillian and Henry M. Stratton-Hans Popper Department of Pathology, Molecular and Cell-Based Medicine, who developed accurate, widespread testing throughout the Health System to help diagnose and manage COVID-19. “Initially, it was conceptualized as a viral respiratory illness. But now we know it causes endothelial damage.” This damage leads to excessive blood clots throughout the body, which can also lead to multi-organ failure. There is a strong immune component to the disease, as well, which is led by macrophages or scavenger blood cells that eat viruses and dead cells and can be very difficult to control, even with targeted immunotherapy.

A clearer understanding of the biology of the disease and the range of organ damage inflicted by COVID-19 was provided by the Department of Pathology, which “uncompromisingly performed as many autopsies as possible, and conducted over 90 in COVID-19-positive patients,” says Mary E. Fowkes, MD, PhD, Professor of Pathology, Molecular and Cell Based Medicine, and Director of Mount Sinai’s Neuropathology and Autopsy Service.

Pulmonary embolism in 3D.

Recently, Drs. Cordon-Cardo and Fowkes published a study of 67 individuals with the disease who were treated at Mount Sinai between March 20 and April 29, 2020. “We expected severe changes in the lungs, which we were able to confirm,” says Dr. Fowkes. “But one of our surprising findings in the lungs was that in addition to the viral infection, there was a secondary bacterial infection that made it worse.” Another surprising finding, she says, was that in a number of cases, the patients had experienced large pulmonary embolisms that traveled directly to the lungs and caused sudden death.

The pathologists also found blood clots in the small blood vessels of many major organs, as well as the central nervous system, and identified a syndrome similar to hemophagocytic lymphohistiocytosis (HLH), a rare condition in which the body makes too many activated immune cells, specifically macrophages and lymphocytes, produced in the bone marrow. HLH can overlap with Kawasaki syndrome, which has been compared to a rare reaction seen in children who seem to recover from COVID-19 but go on to experience severe symptoms that include heart inflammation, low blood pressure, and trouble breathing.

Initially, doctors were concerned that people with asthma would be at greater risk for severe symptoms due to the disease’s respiratory component. But that did not turn out to be the case, even though the disease spreads from one person to another through respiratory droplets. Another surprising finding was that in comparison with the heart, brain, lungs, and liver, the kidneys were less affected by blood clots. Researchers think that may be because the ACE2 receptor—to which the SARS-CoV-2 virus attaches in order to enter the cell—is less prevalent in the kidney’s network of blood vessels.

“In reality, it’s the patients who have heart disease who seem to be at greater risk,” for severe outcomes, says Dr. Fowkes. “Diabetes accelerates vascular disease with plaque located in blood vessels throughout the body. So that if you have pre-existing damage to blood vessels you would be at greater risk. Heart disease is similar. If you have hypertension you see damage to tissues that surround the blood vessels and to the blood vessels themselves.”

Adam Bernheim, MD, Assistant Professor of Diagnostic, Molecular and Interventional Radiology at the Icahn School of Medicine at Mount Sinai, was one of the first U.S. radiologists to review the lung CT scans of COVID-19 patients from China. Since early March, he says, doctors have begun to understand the breadth of injuries that COVID-19 inflicts on the body and its relentlessness in doing so.

“The patterns of injury to the body run the spectrum from blood clots and pulmonary embolisms to pneumonia and abdominal issues,” he says. Some patients, including those in their 20s and 30s, take months to heal and others develop permanent scarring in their lungs. With many diseases he says, the body takes a big hit and then is able to repair itself. But COVID-19 can “cause continuous injury to the lungs over weeks. It just keeps hitting and hitting.”

David L. Reich, MD, President of The Mount Sinai Hospital and Mount Sinai Queens says the last three months illustrated how well the Mount Sinai Health System functioned in ensuring that patients in each of the seven Health System hospitals treating COVID-19 patients received the life-saving care they needed. In addition, he says, “The Icahn School of Medicine, with its top scientists, was completely in lockstep with the largest health system in New York City. We were able to do things together that we never would have been able to do separately. And because of that, we were able to change the course of therapeutics for this disease, as well.”

The Mount Sinai Health System has had the largest worldwide experience with convalescent plasma therapy and was the first to demonstrate its benefit in this disease, he says.  Additionally, Mount Sinai instituted a policy to administer anticoagulant treatment, which has also been beneficial. Through its clinical trials infrastructure, Mount Sinai had early access to the antiviral drug remdesivir, the anti-inflammatory drug sarilumab, and allogeneic stem cell therapy.

During the height of the pandemic, as other health systems “were doing their best to provide some level of care while not being overwhelmed, Mount Sinai was innovating,” says Dr. Reich. “Mount Sinai was applying science and showing improved outcomes with therapeutic innovations in a way that demonstrated we are one of the best institutions in the world, especially with regard to COVID-19 care.”