Nail psoriasis

Approximately 50% of patients with psoriasis have nail involvement (Crowley et al. 2015; Jiaravuthisan et al. 2007). The lifetime incidence of nail abnormalities in psoriatic patients is 80–90% (Crowley et al. 2015; Samman and Fenton 1994). Nail disorders in psoriasis can present commonly as nail pitting and distal separation of the nail plate and less frequently as discoloration and splinter hemorrhages in the nail bed (Jiaravuthisan et al. 2007). Fingernail psoriasis tends to create more problems for patients compared to toenail psoriasis (Crowley et al. 2015). A positive association has been reported between nail abnormalities and the duration of psoriatic skin disease as well as severity of psoriasis (de Jong et al. 1996; de Vries et al. 2013; Armesto et al. 2011). Moreover, nail psoriasis has been noted to be painful for patients, often limiting daily housekeeping and professional tasks (de Jong et al. 1996).

Pitting and deformation are the most common nail dystrophies in psoriasis (de Jong et al. 1996). Pitting manifests as depressions in the topmost layers of the nail plate, with the length of the pit indicating the amount of time that the nail matrix was affected by psoriasis (Jiaravuthisan et al. 2007). Nail matrix psoriasis involves pitting, transverse grooves or Beau’s lines, leukonychia, red spots in lunula, and nail plate crumbling (Zaias 1969; Crowley et al. 2015; Rich and Scher 2003; Pasch 2016; Baran 2014). Nail bed or hyponychium involvement manifests as discoloration, onycholysis, splinter hemorrhages, “oil drop” or “salmon-colored” patches, and subungual keratosis (Zaias 1969; Crowley et al. 2015; Rich and Scher 2003). There is an increased risk of infection with onycholysis, as the separation of the nail plate allows for access and occupation by various microorganisms (Jiaravuthisan et al. 2007). Additionally, subungual keratosis can present as yellow, lubricous nails or a white-silvery counterpart, arising from an inflammatory process as well as accumulation of a glycoprotein (Zaias 1969; Jiaravuthisan et al. 2007). A white-silvery counterpart is the less common form of subungual keratosis seen in psoriatic nails (Jiaravuthisan et al. 2007). Oftentimes, with psoriatic nail changes, there is also evidence of onychomycosis. In toenails especially, a secondary fungal infection can be seen (Crowley et al. 2015). Prior literature indicates a higher incidence of onychomycosis in psoriatic patients than non-psoriatic patients (Klaassen et al. 2014).