#2214 Incidence, risk factors and outcome of calciphylaxis in Iceland
Authors: Palsdottir Gudbjorg Eva , Jonasdottir Asta D , Pálsson Runólfur , Indriðason Ólafur S 
Published: May 2024

Abstract

Background and Aims
Calciphylaxis is a rare and serious medical condition that primarily affects patients with end-stage kidney disease (ESKD). The disorder is characterized by calcium deposition in blood vessels and soft tissues, resulting in skin ulceration and tissue necrosis. The aim of the study was to investigate the incidence, risk factors, and outcomes of calciphylaxis in Iceland.

Method
This was a retrospective case-control study that included individuals diagnosed with calciphylaxis in 1990-2022. Patients were identified by searching electronic medical records (EMR) for the ICD-10 diagnosis codes E83.5 and L94.2, SNOMED histology codes T01000-T03900 in combination with M55400, M55500 or M54000-M54200, documented sodium thiosulfate (STS) therapy, and by consultation with practicing nephrologists. Data on medical history, medication use, and survival were obtained from EMR. A control group of ESKD patients was matched (1:1) based on age, sex, and duration of dialysis. Total annual incidence was calculated per 1,000,000 population of Iceland each year, and for ESKD patients per 10,000 dialysis patients at the end of each year. Poisson regression was used to estimate changes in incidence. Groups were compared using non-parametric tests and survival estimated by Kaplan-Meier method and Cox regression.

Results
Twenty-one cases of calciphylaxis were identified, of which 18 (86%) had ESKD. The average incidence was 2/1,000,000/year. For ESKD patients, the median (interquartile range, IQR) age was 69 (66-75) years, and 50% were women. Three patients (17%) had not yet initiated dialysis at the time of diagnosis and the median duration of dialysis was 0.12 (IQR 0.0-2.8) years. The average incidence of calciphylaxis was 75 per 10,000 dialysis patients/year, increasing by 9.0% annually (Fig. 1). No significant differences between calciphylaxis cases and controls were observed for comorbid diseases or other risk factors. The median body mass index of cases was 29.5 (IQR 27.1-33.7) compared with 27.6 (IQR 24.3-30.6) kg/m2 in controls (p=0.20), and 50% of cases and 22% of controls (p=0.16) were on warfarin treatment at diagnosis. Fifteen patients received treatment with sodium thiosulfate (STS). Three of 6 patients received STS therapy before 2016 and all 12 patients after 2016. One-year mortality of ESKD patients with calciphylaxis was 44%. The median survival was 134 days in 1990-2016, increasing to 644 days after 2016. Survival difference between cases and controls was significant (p=0.04) by log rank test, while adjusted Cox regression did not show a statistically significant association between calciphylaxis and death (HR 2.0 (95% CI, 0.67-6.1)).

Conclusion
The incidence of calciphylaxis in Iceland seems to be increasing and is high compared to incidence rates reported in other countries. Survival, although poor, appears to have improved in recent years. The small sample size is a limitation and further research will require collaborative efforts to generate large patient samples.