Netherton syndrome is a rare disorder inherited in an autosomal recessive pattern consisting of ichthyosiform dermatosis, hair shaft abnormalities (trichorrhexis invaginata), and an atopic diathesis. Patients with Netherton syndrome have been found to have a mutation on chromosome 5q32 in a gene named SPINK5 (serine protease inhibitor, Kazal type-5), which encodes an inhibitor of serine proteases called LEKTI. We report a female patient with previously undiagnosed Netherton syndrome who presented to participate in a clinical research trial investigating the benefit of topical tacrolimus 0.03% ointment [Protopic (Fujisawa Pharmaceutical Co. Ltd., Japan)] for the treatment of atopic dermatitis. This patient was confirmed to have a gene mutation in SPINK5. Current literature suggests a relative contraindication for use of topical tacrolimus in patients with Netherton syndrome owing to concern for increased systemic absorption of the drug. Our patient was not able to tolerate topical tacrolimus owing to local irritation, and did not derive any benefit from therapy. Though rare, when evaluating patients with a possible diagnosis of atopic dermatitis, an index of suspicion for Netherton Syndrome must be maintained. History and overall clinical findings, especially in regards to examination of the hair, will aid in diagnosis.