Monoclonal gammopathy-associated systemic capillary-leak syndrome, also known as Clarkson disease, is a rare condition characterized by recurrent life-threatening episodes of capillary hyperpermeability in the context of a monoclonal gammopathy. This study was conducted to better describe the clinical characteristics, natural history, and long-term outcome of monoclonal gammopathy-associated systemic capillary-leak syndrome.

We conducted a cohort analysis of all patients included in the European Clarkson disease (EurêClark) registry between January 1997 and March 2016. From diagnosis to last follow-up, studied outcomes (eg, the frequency and severity of attacks, death, and evolution toward multiple myeloma) and the type of preventive treatments administered were monitored every 6 months.

Sixty-nine patients (M/F sex ratio 1:1; mean ± SD age at disease onset 52 ± 12 years) were included in the study. All patients had monoclonal gammopathy of immunoglobulin G type, with kappa light chains in 47 (68%). Median (interquartile range) follow-up duration was 5.1 (2.5-9.7) years. Twenty-four patients (35%) died after 3.3 (0.9-8) years. Fifty-seven (86%) patients received at least one preventive treatment, including intravenous immunoglobulins (IVIg) n = 48 (73.8%), theophylline n = 22 (33.8%), terbutaline n = 22 (33.8%), and thalidomide n = 5 (7.7%). In the 65 patients with follow-up, 5- and 10-year survival rates were 78% (n = 35) and 69% (n = 17), respectively. Multivariate analysis found preventive treatment with IVIg (hazard ratio 0.27; 95% confidence interval, 0.10-0.70; P = .007) and terbutaline (hazard ratio 0.35; 95% confidence interval, 0.13-0.96; P = .041) to be independent predictors of mortality.

We describe the largest cohort to date of patients with well-defined monoclonal gammopathy-associated systemic capillary-leak syndrome. Preventive treatment with IVIg was the strongest factor associated with survival, suggesting the use of IVIg as the first line in prevention therapy.