Psoriatic transversal nail grooves on biologics
Transverse grooves on the nails of a psoriasis vulgaris patient being treated with ixekizumab were noticed. The indentation might have appeared during the period when the effective concentration of ixekizumab was low and psoriasis activity in the nail matrix had increased shortly before the monthly dose.

A 47-year-old man with a history of psoriasis vulgaris for 15 years was treated using ixekizumab, a selective humanized neutralizing monoclonal antibody against IL-17A. The eruption was well controlled, and arthropathy did not occur. He was prescribed 80 mg of Ixekizumab as a monthly self-administered dose. We noted three transverse grooves on the patient's left middle fingernail at one consultation.

These appeared equidistant, with normal nail gloss and quality between them. However, peripheral circulatory failure was absent. The transverse grooves that appeared similar to the annular rings of a tree were the deformed nail similar to nail dystrophy produced when the effective blood concentration of ixekizumab was low, and the psoriatic activity in the nail matrix was high, shortly before the monthly administration of ixekizumab. In contrast, the nails produced during effective antibody concentration had a normal shape.

The serum ixekizumab concentration showed peak level 4 days after injection with gradual decline1; however, stable trough concentration during the long-term use with individual differences. Since drug concentration was not measured in the current case, the grooves might be considered a finding indicating residual activity.