Can psoriasis cause elevated lymphocyte levels?

Can Psoriasis Cause High Lymphocytes?

Yes, psoriasis can cause elevated lymphocyte levels due to its underlying immunopathogenesis involving T-cell mediated inflammation, particularly with increased CD4+ T helper cells, CD8+ T cells, and Th17 cells in the peripheral circulation.

Immunological Basis of Psoriasis and Lymphocyte Involvement

Psoriasis is a chronic inflammatory disease with a strong immunologic basis. The pathogenesis involves dysregulated interplay between the epidermis, dermis, cutaneous microvasculature, and the immune system 1. Key immunological features include:

• T-cell infiltration: Psoriatic synovial tissue is characterized by T-cell infiltrates with increased vascularity 1
• Altered lymphocyte populations: Patients with active psoriasis show significantly higher proportions of:
  • CD4+ T helper cells
  • CD8+ T cytotoxic cells
  • CD4+CD161+ Th17 cells 2

Specific Lymphocyte Abnormalities

Recent high-dimensional analysis using mass cytometry has identified three new lymphocyte subsets that are abundant in psoriasis peripheral blood:

1. CD3-CD4+ lymphoid tissue inducer cells
2. Tc17 cells
3. CD8+CXCR3+ Tregs 3

Inflammatory Markers in Psoriasis

Multiple studies have demonstrated altered inflammatory markers in psoriasis patients compared to healthy controls:

• Elevated white blood cell counts: Total WBC, neutrophil, and platelet counts are higher in psoriasis patients 4
• Neutrophil-to-lymphocyte ratio (NLR): Significantly elevated in psoriasis patients compared to controls 5, 4
• Lymphocyte abnormalities: Psoriasis patients show altered lymphocyte function with decreased regulatory T cells (CD4+CD25+ Treg cells) 2

Relationship to Disease Severity

The relationship between lymphocyte counts and disease severity shows some variability:

• Some studies show no significant correlation between NLR and PASI score (Psoriasis Area and Severity Index) 5
• Other research demonstrates that CD3-CD4+ cells have elevated OX40 and decreased FRA2 expression, which positively correlates with PASI 3

Different Psoriasis Subtypes and Lymphocyte Profiles

Lymphocyte abnormalities vary between psoriasis subtypes:

• Generalized pustular psoriasis (GPP) shows the highest NLR values
• Psoriasis vulgaris (PsV) has significantly lower NLR than GPP, erythrodermic psoriasis (PsE), and arthritic psoriasis (PsA) 4

Clinical Implications

The elevated lymphocyte levels in psoriasis have important clinical implications:

1. Lymphoma risk: Patients with psoriasis have an increased risk of developing lymphoma, particularly Hodgkin's lymphoma (RR 3.18) and cutaneous T-cell lymphoma (RR 10.75) 1

2. Treatment considerations:

   • NB-UVB phototherapy has been shown to reduce circulating Th1 and Th17 cells while increasing Treg cell levels 2
   • Biologic therapies targeting specific immune pathways may normalize lymphocyte profiles

Monitoring Recommendations

For patients with psoriasis who show elevated lymphocyte counts:

• Regular monitoring of complete blood counts is prudent
• Consider lymphocyte subset analysis in cases of persistent lymphocytosis
• Be vigilant for signs and symptoms of lymphoma, particularly in patients with severe disease

In conclusion, the elevated lymphocyte levels seen in psoriasis reflect the underlying immune dysregulation central to the disease pathogenesis, with specific patterns of T-cell subset abnormalities that may vary with disease subtype and severity.