The COVID-19 outbreak has been declared the sixth Public Health Emergency of International Concern certified by the World Health Organization. With the extensive application of COVID-19 vaccines, rare but serious adverse reactions have gradually emerged, among which systemic capillary leak syndrome (SCLS) deserves our attention. SCLS is difficult to diagnose. Not only can it exacerbate various diseases, but also can lead to pulmonary edema, kidney failure, and even death. We summarized and discussed case reports of SCLS induced by COVID-19 vaccines to raise awareness of COVID-19 vaccine-associated rare diseases. We conducted a comprehensive search in Web of Science, PubMed and Embase and collected case reports of SCLS induced by COVID-19 vaccine before February 19, 2024. We identified and analyzed 12 articles, encompassing 15 cases. We synthesized the data to summerize possible mechanisms of SCLS, clinical manifestations, differential diagnoses, and therapeutic approaches. Most SCLS occurred after vaccination with the Pfe-Biontech mRNA vaccine (9/15) and following the second vaccination (10/15). Almost all patients experienced hypotension (13/15) and tachycardia (11/15). Most patients received intravenous fluids (9/15) and corticosteroids (9/15). 11 patients were recovered and were discharged, while 4 patients died. Inflammation and endothelial cell damage may be linked to SCLS and COVID-19 vaccines. These findings highlight the necessity of focusing on serious adverse reactions of COVID-19 vaccines and the urgency to reconsider the safety of COVID-19 vaccines.

Systemic capillary leak syndrome (SCLS) is a rare entity that is frequently idiopathic or, rarely, associated with infections, autoimmune diseases, drugs, surgery, and cancer. Several cancers can directly cause SCLS, although it is very uncommon as the inaugural presentation of a non-Hodgkin lymphoma. We report a case of SCLS as a paraneoplastic syndrome which revealed a large B-cell lymphoma, a non-Hodgkin lymphoma of B-cell origin.

Immune checkpoint inhibitors (ICIs) are now being widely used for the treatment of various malignancies, but they have a distinctive set of side effects due to the overactivation of the immune system, which is important to recognize. Capillary leak syndrome (CLS) is a rare but potentially life-threatening side effect of ICIs that causes a significant increase in the permeability of capillaries, leading to the leakage of plasma-containing proteins from these small vessels. This condition results in several clinical features, including edema, hypotension, hypoalbuminemia, and hemoconcentration. Timely recognition and discontinuation of the offending immunotherapy can optimize outcomes. Treatment is focused on supportive care and prompt initiation of immunosuppressants, such as steroids.

We present a case study of a young male with a history of 22q11.2 deletion syndrome (22qDS), diagnosed with systemic capillary leak syndrome (SCLS) who presented with acute onset of diffuse anasarca and sub-comatose obtundation. We hypothesized that his co-presentation of neurological sequelae might be due to blood-brain barrier (BBB) susceptibility conferred by the 22q11.2 deletion, a phenotype that we have previously identified in 22qDS. Using pre- and post-intravenous immunoglobulins (IVIG) patient serum, we studied circulating biomarkers of inflammation and assessed the potential susceptibility of the 22qDS BBB. We employed in vitro cultures of differentiated BBB-like endothelial cells derived from a 22qDS patient and a healthy control. We found evidence of peripheral inflammation and increased serum lipopolysaccharide (LPS) alongside endothelial cells in circulation. We report that the patient\'s serum significantly impairs barrier function of the 22qDS BBB compared to control. Only two other cases of pediatric SCLS with neurologic symptoms have been reported, and genetic risk factors have been suggested in both instances. As the third case to be reported, our findings are consistent with the hypothesis that genetic susceptibility of the BBB conferred by genes such as claudin-5 deleted in the 22q11.2 region promoted neurologic involvement during SCLS in this patient.

Idiopathic systemic capillary leak syndrome (ISCLS) is a rare disease characterized by hypotensive shock, anasarca, hemoconcentration, and hypoalbuminemia. Despite the life-threatening course of the disease, no treatment strategy has been established. A 68-year-old man presented with hypotensive shock following a prodrome. Based on the characteristic blood test findings, ISCLS was suspected. The patient was resuscitated by administering massive amounts of fluids and inotropic and vasopressor agents. After his blood pressure had stabilized, renal replacement therapy (RRT) was promptly initiated to facilitate the removal of excess fluid, despite the presence of urine output. Typically, ISCLS has three phases: prodromal, leak, and post-leak. Diuresis should be promptly induced during the transition from the leak phase to the post-leak phase to avoid fatal complications such as pulmonary edema. We propose that in patients with ISCLS, early introduction of RRT is recommended if indicated.

Idiopathic systemic capillary leak syndrome (ISCLS) is a rare condition caused by the extravasation of intravascular fluids and proteins into the interstitial space due to increased vascular endothelium permeability. It is characterized by episodes of hypotension, hypoalbuminemia, and hemoconcentration with generalized edema. Its etiopathogenesis is unknown. However, it is associated with monoclonal gammopathy in more than 80% of cases. There is currently no targeted treatment, and the approach during a crisis is supportive, mainly to control blood pressure, maintain perfusion of vital organs, and prevent complications, such as acute pulmonary edema and organ failure due to ischemia, which are the primary causes of death. We present the case of a 72-year-old man with generalized edema and pleural, pericardial, and peritoneal effusions whose laboratory results showed hypoalbuminemia, hypoproteinemia, and immunoglobulin G kappa monoclonal gammopathy. Other etiologies for severe hypoalbuminemia with anasarca were excluded after an exhaustive complementary study, leading to the diagnosis of ISCLS associated with monoclonal gammopathy. The patient showed progressive clinical improvement with albumin and diuretic therapy. However, they were readmitted to the hospital due to hypotension with multiorgan dysfunction and died a few hours later.

Systemic Capillary Leak Syndrome (SCLS) is a rare disease that causes severe distributive shock provoked by infection or vaccination. SCLS is clinically diagnosed by a triad of distributive shock, paradoxical hemoconcentration, and hypoalbuminemia. SCLS associated with coronavirus disease (COVID-19) in adults has not been reported yet in Japan. Case 1: A 61-year-old woman with fever, sore throat, headache, and muscle pain was admitted to our emergency department with suspected COVID-19. She had been diagnosed with SCLS 3 years earlier. Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) antigen and polymerase chain reaction (PCR) tests were negative at admission. She went into shock in the emergency department and was treated for septic shock. The following day, the SARS-CoV-2 PCR test was positive. She did not respond to fluid resuscitation and catecholamine and finally died. Case 2: A 58-year-old man was admitted to our hospital for de-saturation due to COVID-19. He got into shock on day 3. SCLS was suspected, and 5 g of intravenous immunoglobulin and 5% albumin were administered for sepsis treatment. He responded to the aggressive fluid therapy within 48 h and was finally discharged. COVID-19 can trigger SCLS, and early recognition of SCLS is crucial for survival. Primary care physicians should consider SCLS when they observe distributive shock and paradoxical hemoconcentration deviations from the natural course of COVID-19.

The unprecedented impact and sequelae of COVID-19 infection are not yet fully understood, and better understanding of the pathophysiology of these infections is needed. Endothelial dysfunction might be common sequelae associated with COVID-19, and increased inflammatory responses, oxidative stress, proinflammatory cytokines, and impaired mitochondrial function also contribute to the pathophysiology of post COVID-19 medical disorders. Systemic capillary leak syndrome following COVID-19 infection, both new onset and exacerbation of a prior disorder, has been reported. The pathophysiology of SCLS is uncertain; it likely develops during transient vascular endothelial dysfunction or endotheliopathy and inflammation resulting from circulating humoral factors. Here, we report a case of adult patient with 2 episodes of systemic capillary leak syndrome following prior COVID-19 infection. This patient had a transient response to intravenous IgG.

Systemic capillary leak syndrome (SCLS) is a rare and complex adverse effect of immune checkpoint inhibitors (ICIs). The diagnosis of drug-induced SCLS is based on diffuse infusions of exudative fluid into the interstitial areas and the exclusion of other causes. The best management of ICIs-induced SCLS is not settled, though proper supportive care and corticosteroids were commonly applied as the first-line treatment. In our patient with advanced gastroesophageal junction squamous cell carcinoma, although ICIs-induced SCLS was successfully controlled with corticosteroids, the patient soon experienced cancer progress and died of pulmonary infections. Based on our experience and the reported cases by other hospitals, different stages of SCLS might respond differently to the same treatment. Therefore, a grading of ICIs-induced SCLS might help to stratify the patient for different treatment strategies. Besides, corticosteroids-sensitive patients, though waived from deadly SCLS, might be at higher risk of cancer progress and subsequent infections due to the application of corticosteroids. Considering that the inflammatory factors should be closely involved in the development of ICIs-induced SCLS, targeted therapy against the driver inflammatory cytokine might offer treatment regimens that are more effective and safer.

Systemic capillary leak syndrome (SCLS), also known as Clarkson\'s disease, is a rare and potentially lethal condition characterized by hypotension, hemoconcentration, and hypoalbuminemia; however, the cause of SCLS is still uncertain. We present the case of a 62-year-old male with flu-like symptoms who presented to the emergency department with shock. Initial evaluation revealed hemoconcentration, hypoalbuminemia, acute kidney failure, and positive polymerase chain reaction (PCR) for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Despite aggressive fluid resuscitation, the shock persisted, and the patient\'s condition deteriorated. After ruling out ischemia and septic shock, the patient was diagnosed with coronavirus disease 2019 (COVID-19)-associated SCLS. Treatment with remdesivir and intravenous immunoglobulin (IVIG), along with the restoration of intravascular volume, led to the gradual improvement of the patient\'s condition. The patient experienced pulmonary edema, which was managed by correcting the fluid balance through continuous hemodiafiltration. Eventually, the patient recovered without any residual organ complications. SCLS is often misdiagnosed because of its rarity and non-specific symptoms. Accurate diagnosis and understanding of the disease\'s pathophysiology are crucial for effective management. This report contributes to the existing literature by presenting a case of COVID-19-associated SCLS and emphasizes the need for further research on its occurrence and outcomes.