Severe Nail Fold Psoriasis Extending from Nail Psoriasis Resolved with Ustekinumab: Suggestion of a Cytokine Overflow Theory in the Nail Unit

Abstract

Because nail psoriasis is difficult to treat, therapy with many biological drugs has been attempted. Ustekinumab is approved for chronic plaque psoriasis and psoriatic arthritis (PsA), with some trials reporting nail improvement using this agent. A 51-year-old man with severe chronic plaque psoriasis had severe involvement of all fingernails and toenails, with accompanying nail fold psoriasis. He also had PsA of the small joints of the fingers. Despite multiple conventional therapies, the nail lesions did not improve, and his nail psoriasis severity index score was 97. After a fourth ustekinumab injection, most of the fingernail psoriasis was resolved, and only hyperkeratosis remained on both large toenails. Because the nail plate, nail fold, and small joints of the fingers are closely apposed structures within a small area, cytokines produced from the nail units overflow to the nail fold and small joints and can induce nail fold psoriasis and PsA.

Keywords: Arthritis; Nail diseases; Psoriasis; Psoriatic; Severity of illness index; Ustekinumab.

Fig. 1. Severe 20-nail and nail fold psoriasis before ustekinumab treatment. Fingernails showing relatively less change than the toenails because of the effect of repetitive triamcinolone intralesional injections. Proximal nail fold atrophy caused by steroid injection can be seen.

Fig. 2. Improvement in nail psoriasis after the fourth injection of ustekinumab. There is complete remission of fingernail psoriasis. Both large toenails show subungual hyperkeratosis, which was completely resolved after treatment.