Phenotypic familial aggregation in chronic chilblains.

BACKGROUND

Our clinical observations and two earlier studies indicate familial clustering to be involved in chronic chilblains. Demonstrating phenotypic familial aggregation is a next step to investigate the origin of familial clustering.

OBJECTIVE

This study was initiated to assess evidence for phenotypic familial aggregation in chronic chilblains.

METHODS

Using a case-control family design in a primary care setting, we computed the familial relative risk of at least one episode of chronic chilblains during life with 95% confidence intervals (CIs). The study population consisted of 192 relatives of 31 case probands (at least one confirmed episode of chronic chilblains). The control population consisted of 178 relatives of 31 sex- and age-matched index controls (no history of chronic chilblains).

RESULTS

The familial relative risk of chronic chilblains was 3.6 (95% CI 1.9-7.3). Additional sensitivity analysis shows similar figures.

CONCLUSION

We demonstrate robust phenotypic familial aggregation in chronic chilblains.