The genetics of allergic contact hypersensitivity to nickel.

We have examined evidence for familial disposition to nickel allergic contact dermatitis (Ni ACD). 258 patients attending for routine patch testing were recruited prospectively. 39 patients were diagnosed with Ni ACD. 31 of 209 1st-degree relatives (15%) of probands had a history of nickel hypersensitivity. 84 patients with no history of nickel hypersensitivity and negative patch tests to nickel were used as controls. 24 of 458 1st degree relatives of controls (5.2%) had a history of Ni ACD. The risk ratio for 1st degree relatives of a patient with Ni ACD is 2.83 (95% confidence intervals are 2.45, 3.27). This is the 1st study to present a statistic to represent risk to relatives of developing ACD. Relatives of patients with Ni ACD have an increased risk of developing the condition, but the genetic basis for this is not yet known. With currently available techniques, this value of relative risk makes a positional cloning approach to gene identification impractical.