Description

• Acute manifestations
  • Formation of multiple, sterile, painful pustules that have an erythematous base located surrounding and under the nail(s) that coalesce to form polycyclic “lakes of pus,” which subsequently rupture and crust
• Chronic sequelae
  • Nail changes: paronychia, onychodystrophy, onycholysis, onychomadesis, and anonychia
  • Scaling of the nail bed and periungual skin
  • Sclerosis or atrophy of soft tissue adjacent and deep to nail bed
  • Osteolysis of underlying bone, particularly distal phalanges
• Distribution
  • Typically affect distal extremities, affecting 1 to 2 digits, most frequently the 1st digits of the hands; can involve all fingers and toes
  • Predilection for dorsal surfaces of hands and feet
  • Spare the central palmar/plantar regions
  • Rarely spread proximally to involve feet, ankles, hands, and forearms. Isolated proximal psoriatic plaques are rare.

Epidemiology

• Exceedingly rare: Only case studies and series are available.
• Female predominance
• Predominantly in adults but also seen in children: observed in 4.7% cases of infantile psoriasis in one series

Etiology and Pathophysiology

• Immune dysregulation: Acute-phase reactants such as IL-1 and IL-36 likely play a role in pathogenesis (1).
• In some instances, digital trauma or infection may be an inciting event.

Genetics

• Reported associations with mutations in the IL36RN gene, which codes for the IL-36 receptor antagonist and is a cause of familial generalized pustular psoriasis (1,2)
• No observed relationship with plaque psoriasis–associated alleles HLA-B13, HLA-B17, or HLA-BW37

Risk Factors

• History of psoriasis, particularly pustular variant
• Digital trauma
• Local infection
• Smoking may contribute to exacerbations.