Significant absorption of topical tacrolimus in 3 patients with Netherton Syndrome

Background: Tacrolimus is a macrolide immunosuppressant approved in oral an d intravenous formulations for primary immunosuppression in liver and kidne y transplantation. Topical 0.1% tacrolimus ointment has recently been shown to be effective in atopic dermatitis for children as young as 2 years of a ge, with minimal systemic absorption. We describe 3 patients treated with t opical 0.1% tacrolimus who developed significant systemic absorption. Observation: Three patients previously diagnosed as having Netherton syndro me were treated at different centers with 0.1% tacrolimus ointment twice da ily. Two patients showed dramatic improvement. All patients were found to h ave tacrolimus blood levels within or above the established therapeutic tro ugh range for oral tacrolimus in organ transplant recipients. None of these patients developed signs or symptoms of toxic effects of tacrolimus. Conclusions: Patients with Netherton syndrome have a skin barrier dysfuncti on that puts them at risk for increased percutaneous absorption. The Food a nd Drug Administration recently approved 0.1% tacrolimus ointment for the t reatment of atopic dermatitis. Children with Netherton syndrome may be misd iagnosed as having atopic dermatitis. These children are at risk for marked systemic absorption and associated toxic effects. If topical tacrolimus is used in this setting, monitoring of serum tacrolimus levels is essential.