Case Presentation: A 68-year-old Chinese man was admitted for giddiness, lethargy and lower limb oedema for 1 day. He had no significant past medical history. Clinical examination revealed that he was dehydrated and hypotensive, with a systolic blood pressure of 70 mmHg. Examination of his cardiovascular, respiratory and abdominal systems was unremarkable. Blood investigations were significant for polycythaemia (Hb of 21.7 g/dL), elevated creatinine (128 mmol/L) and hypoalbuminemia (16 g/L). He responded to intravenous fluids initially but went into cardiac arrest 4 hours later. He was successfully resuscitated and admitted to the intensive care unit. During his stay in ICU, he was treated with antibiotics and required inotropic support. He was negative for Jak2 mutation. The patient’s condition subsequently improved. Polycythaemia was deemed to be due to haemoconcentration from dehydration, with his Hb at 10 g/dL on discharge.The patient was admitted 3 more times over the next 4 years, with hypotension, polycythaemia and hypoalbuminemia during each episode. Based on the clinical features, he was diagnosed with systemic capillary leak syndrome (SCLS), also known as Clarkson disease. Myeloma panel showed monoclonal gammopathy.

Discussion: SCLS was first described in 1960. It is a rare disorder, with approximately 300 cases reported worldwide. It is diagnosed clinically and characterized by (1) hypotension, (2) haemoconcentration and (3) hypoalbuminemia. It has been reported in all age groups. It is most commonly reported in the Caucasian population, but this is likely a result of poor recognition. It has since been reported in Asian, African American, Hispanic and Middle Eastern patients. There is no sex predominance.During acute attacks, dysfunction in vascular endothelium results in leakage of plasma proteins and intravascular fluid into the interstitial compartment. This results in haemoconcentration and hypotension. Patients develop peripheral oedema and hypotension, with severe cases developing multi-organ failure and cardiopulmonary collapse. Treatment of acute attacks is supportive with intravenous fluids. The fluid extravasation phase usually lasts for a few days. Recovery is then characterized by a decrease in the amount of intravenous fluids required to maintain adequate intravascular volume. During this period, there is a high risk for volume overload and pulmonary oedema as extravasated fluid is recruited back into intravascular space.As SCLS has a similar presentation as conditions like severe sepsis and anaphylaxis, it is under-recognized and diagnosis is oftentimes delayed. It has been associated with the presence of monoclonal gammopathy in 60 to 80 percent of cases. There is still no standard prophylactic therapy, though studies have shown that IVIG, terbutaline and theophylline decrease attack frequency and mortality rates.

Conclusions: SCLS remains a rare disease. It is diagnosed based on clinical features. It is thus under-recognized and patients experience delays in diagnosis. As it is potentially life-threatening, recognition is important, as patients with SCLS can be counselled to seek medical attention during the early phase of an acute attack.