Topical Cyclosporine Suspension for the Treatment of Brittle Nails

Brittle nail syndrome (BNS) is a heterogeneous abnormality, characterized by increased fragility of the nail plate. About 20% of the population is affected by brittle nails and women are affected twice as frequently as men. (2). The diagnostic criteria for brittle nails are not well defined but most authors agree in at least these 3 criteria: onychoschizia (lamellar splitting of the free edge and distal portion of the nail plate), onychorrhexis (longitudinal thickening and thinning or ridging of the nail plate) and fraying or raggedness of the distal edge causing transverse splitting.

Although the cause of nail brittleness is unknown, most authors believe that it is caused by dehydration of the nail plate and that frequent cycles of hydration and dehydration as well as various mechanical and chemical insults increase the incidence of brittle nails. (7) The nail plate contains about 15% water and a very low lipid content so water permeation through the nail plate is high.(8) In fact, it has been demonstrated that the flux of water across the nail plate is 10 times more than the epidermis and 1000 times more permeable than the stratum corneum.(9) A recent report show that there was no significant difference in water content of brittle nails when compared to normal nails and suggested that nail plate water content is random and that nail plates are in a constant state of influx and efflux of water. (10) Keratoconjunctivitis sicca is a chronic, bilateral desiccation of the conjunctiva and cornea due to an inadequate tear film. There are two types: one caused by an inadequate tear volume and the other one caused by an accelerated tear evaporation due to poor tear quality (11). Restasis® (cyclosporine 0.05% topical emulsion) is effective in treating keratoconjunctivitis sicca.

BNS and keratoconjunctivitis sicca have in common a disruption of water balance which gives rise to problematic clinical disorders. We hypothesize that a product which improves corneal dehydration would also be effective for brittle nails. Our rationale for using occlusion is that is has been shown that occluding the skin with a vapor-permeable membrane increases the water flux and the barrier function is recovered at a normal rate. (12) We also hypothesize that using Restasis® (cyclosporine 0.05% topical emulsion) or its vehicle (Refresh Dry Eye Therapy®) under occlusion with a finger cot will increase the nail plate hydration balance and as a consequence will improve nail brittleness. Topical cyclosporine has been shown to be safe in the treatment of other dermatological conditions such as nail psoriasis and oral lichen planus. (13,14) An investigator-blinded design will differentiate if the observed effects are caused by the active ingredient in Restasis® (cyclosporine 0.05% topical emulsion) or its vehicle (Refresh Dry Eye Therapy®).