Hypothesis--the natural selection of psoriasis

Area of Science:

• Immunology
• Genetics
• Dermatology

Background:

• Psoriasis is a common inherited skin disorder, particularly in northern populations.
• Streptococcal infections, like scarlet fever, trigger psoriasis and historically had high childhood mortality.
• Immune responses to streptococcal antigens, specifically delayed-type hypersensitivity, are altered in psoriasis patients.

Purpose of the Study:

• To explore the potential survival advantage conferred by psoriasis.
• To investigate the link between psoriasis prevalence and historical environmental hazards like scarlet fever.
• To examine the role of altered immune responses in this potential protective effect.

Main Methods:

• The study reviews existing literature on psoriasis, scarlet fever, and immune responses.
• It analyzes the relationship between streptococcal infections, delayed-type hypersensitivity, and disease severity.
• The Dick test's historical use for assessing scarlet fever susceptibility is considered.

Main Results:

• Psoriatic patients exhibit a decreased cutaneous delayed-type hypersensitivity response to streptococcal antigens.
• This altered immune response may ameliorate the severity and mortality associated with scarlet fever.
• The pathogenesis of scarlet fever involves both primary and secondary streptococcal toxicity, including hypersensitivity.

Conclusions:

• The high genetic frequency of psoriasis may be an evolutionary adaptation providing protection against streptococcal infections.
• Altered immunological mechanisms in psoriasis patients could explain a reduced susceptibility or severity to scarlet fever.
• This suggests a potential survival advantage linked to psoriasis prevalence in certain populations.