What are the precipitating factors and risk factors for psoriasis, including percentages?

Precipitating Factors and Risk Factors for Psoriasis

Psoriasis is triggered by an interplay of genetic susceptibility, environmental exposures, medications, infections, and lifestyle factors, with the HLA-Cw6 allele being the major genetic risk factor and obesity, smoking, alcohol, stress, skin trauma, and certain medications serving as the most clinically significant precipitating factors. 1, 2, 3

Genetic Risk Factors

• HLA-Cw6 allele (PSORS1) is the major susceptibility gene for psoriasis 1, 2
• At least 8 chromosomal loci (PSORS I-VIII) have been identified with statistically significant linkage to psoriasis 1, 2
• Psoriasis is a complex genetic disease of dysregulated inflammation, though the complete mechanism of inheritance remains undefined 1

Environmental and Physical Precipitating Factors

Skin Trauma (Koebner's Phenomenon)

• Physical injury to the skin can trigger psoriasis lesions at the site of trauma 1, 2, 4
• This represents one of the most well-documented environmental triggers 2

Infections

• Streptococcal infections are particularly associated with guttate psoriasis, which frequently appears abruptly after bacterial or viral febrile episodes of upper respiratory inflammation 1, 5
• Bacterial superantigens such as streptococcal antigens can exacerbate psoriasis 1
• Systemic viral infections show increased risk in psoriasis patients 1

Weather and Climate

• Cold weather may exacerbate psoriasis manifestations 4

Lifestyle and Behavioral Risk Factors

Obesity

• 65% of people older than 20 years in the United States are either overweight or obese (BMI >25) 1
• In the Nurses Health Study II (78,626 women followed for 14 years), obesity and weight gain were strong risk factors for developing psoriasis in women 1
• The relative risk of developing psoriasis was highest in those with the highest BMIs, while a low BMI (<21) was associated with lower risk 1
• Increased adiposity and weight gain are strong risk factors for psoriasis development 1
• Higher BMI is associated with increased risk of developing psoriasis and may worsen existing disease 2

Smoking

• Smoking is a well-documented behavioral risk factor that may be provoked by the psychosocial burden of the disease 1
• Smoking is associated with increased cardiovascular risk in psoriasis patients 1

Alcohol Consumption

• Multiple studies have shown that increased alcohol use and abuse are independent risk factors for psoriasis 1
• A positive dose-response relationship between alcohol intake and psoriasis severity was demonstrated in women in one prospective study 1
• Alcohol can precipitate or worsen psoriasis in individuals with a history of the condition 6, 2
• Men with higher pretreatment daily average alcohol consumption showed less treatment-induced improvement 1

Psychological Stress

• Psychological stress is a well-documented trigger for psoriasis flares 2, 4
• Excessive stress (both physical and psychological) may trigger or exacerbate the disease 4

Medication-Induced Precipitating Factors

High-Risk Medications

• Lithium can cause severe, even life-threatening deterioration of psoriasis in patients with pre-existing disease 6, 2, 4
• Antimalarials (chloroquine, hydroxychloroquine) can severely worsen pre-existing psoriasis 6, 2
• Beta-blockers can exacerbate pre-existing psoriasis or trigger new onset in susceptible individuals, with stronger association in long-term use 6, 2, 4
• NSAIDs (non-steroidal anti-inflammatory drugs) can worsen existing psoriasis 6, 2
• TNF inhibitors can paradoxically trigger psoriasis in some patients despite being used to treat the condition 6, 2

Cytokine Therapies

• Exacerbation of psoriasis occurs with certain cytokine therapies including interferons alfa, beta, and gamma; interleukin (IL)-2; and granulocyte colony-stimulating factor 1

Associated Comorbidities as Risk Indicators

Metabolic Syndrome

• 34% of psoriasis patients met criteria for metabolic syndrome compared with 26% of controls (OR 1.50,95% CI 1.40-1.61) 1
• Individual components significantly more common in psoriasis patients include:
  • Obesity: 38% vs 31% in controls (OR 1.38) 1
  • Elevated triglycerides: 36% vs 28% (OR 1.49) 1
  • Hypertension: 31% vs 28% (OR 1.20) 1
  • Elevated glucose: 22% vs 16% (OR 1.44) 1

Cardiovascular Disease

• Psoriasis patients have increased frequency of hyperlipidemia, hypertension, insulin resistance, diabetes mellitus, and homocysteinemia 1
• The chronic inflammatory nature of psoriasis itself may be an independent risk factor for atherosclerosis and myocardial infarction 1

Mental Health

• Prevalence of depression in psoriasis patients is approximately 24% 1
• Psoriasis patients are at least 1.5 times more likely to have depression than controls 1
• Psoriasis patients had significantly increased risk for anxiety (OR 2.91,95% CI 2.01-4.21) and depression (OR 3.01,95% CI 1.86-4.90) 1

Inflammatory Bowel Disease

• Likelihood of Crohn's disease was 0.92% for psoriatic patients versus 0.45% for controls 1
• Likelihood of ulcerative colitis was 1.1% for psoriasis patients versus 0.56% for controls (prevalence rate 1.91) 1

Clinical Implications

Identifying and avoiding triggers is an important aspect of psoriasis management 2. For medication-induced psoriasis, consider alternative therapies when possible, though discontinuation must be balanced against the need for the medication 2. Weight management may help reduce psoriasis severity in overweight patients 2. Patients should be counseled on smoking cessation, achieving ideal BMI, exercising 3 times weekly for 30 minutes, and moderating alcohol intake 1.