What is the relationship between psoriasis and streptococcal infections?

Relationship Between Psoriasis and Streptococcal Infections

Guttate psoriasis has the strongest established relationship with streptococcal infections, particularly group A beta-hemolytic streptococci, which can trigger the onset of this psoriasis subtype in genetically predisposed individuals. 1

Specific Relationships by Psoriasis Subtype

Guttate Psoriasis

• Strong association with streptococcal infections

  • Characterized by small (1-10mm), salmon-pink, drop-like papules with fine scale 1
  • Most commonly affects individuals younger than 30 years 1
  • Typically appears on the trunk and proximal extremities 1
  • Accounts for less than 2% of psoriasis cases 1

• Pathophysiologic mechanism:

  • Streptococcal infections trigger an immune response that cross-reacts with skin antigens 2
  • Serologic evidence of recent streptococcal infection is present in 58% of patients with acute guttate psoriasis 3
  • Group A beta-hemolytic streptococci are isolated from 26% of patients with acute guttate psoriasis compared to 7% of controls 3
  • Streptococcal-specific T lymphocytes have been isolated from guttate psoriatic lesions 4

• Clinical considerations:

  • Most commonly follows pharyngitis, but can be triggered by streptococcal infections at other sites, including perianal region 5
  • Multiple streptococcal serotypes can trigger guttate psoriasis, suggesting the trigger is not serotype-specific 3
  • Often self-limiting, but may require treatment 1
  • Repeated attacks following documented tonsillitis may warrant referral to otolaryngologist for consideration of tonsillectomy 1

Pustular Psoriasis

• Limited association with streptococcal infections
  • Characterized by sterile pustules on erythematous base 1
  • Can be localized (palms and soles) or generalized 1
  • No strong evidence linking streptococcal infections to pustular psoriasis in the literature reviewed 1

Erythrodermic Psoriasis

• No established relationship with streptococcal infections
  • Characterized by widespread erythema and scaling affecting >90% of body surface area 1
  • Can be life-threatening due to impaired thermoregulation and barrier function 1
  • Increased risk of staphylococcal septicemia rather than streptococcal infections 1
  • No evidence linking streptococcal infections to erythrodermic psoriasis in the literature reviewed 1

Management Implications

1. For guttate psoriasis:

   • Investigate for streptococcal infection (throat swab, perianal examination) 1, 5
   • Treat documented streptococcal infections with appropriate antibiotics (phenoxymethyl penicillin or erythromycin) 1
   • Consider UVB phototherapy for widespread lesions 1
   • Low concentrations of tar and dithranol may be helpful but are less tolerated in acute eruptions 1

2. For chronic plaque psoriasis with exacerbations:

   • Consider streptococcal throat infections as potential triggers for flares 6
   • Patients with chronic psoriasis report sore throats significantly more often than controls 6
   • Early treatment of streptococcal throat infections might be beneficial in preventing exacerbations 6

Clinical Pearls and Pitfalls

• Pitfall: Failing to investigate for streptococcal infection in patients presenting with guttate psoriasis

  • Solution: Always perform throat swabs and consider perianal examination, especially in children 5

• Pitfall: Overlooking streptococcal infections as triggers for exacerbation in chronic plaque psoriasis

  • Solution: Encourage patients with chronic psoriasis to report sore throats promptly for evaluation 6

• Pitfall: Assuming all psoriasis subtypes have equal association with streptococcal infections

  • Solution: Recognize that guttate psoriasis has the strongest established relationship with streptococcal infections 1, 3

• Pitfall: Focusing only on throat infections

  • Solution: Consider other sites of streptococcal infection, including perianal region, especially in children 5