Psoriasis is a chronic, systemic T-cell mediated autoimmune skin disease, 
potentially associated with arthritis. The new understanding of 
immunopathogenesis and inflammatory cytokine pathways was actually the rationale 
for developing and introducing biological drugs in the treatment of moderate to 
severe psoriasis and psoriatic arthritis. Different from the traditional 
systemic drugs that impact the entire immune system, bio-logics target only 
specific points of the immune system. This review focuses on five biologics 
which target either T-cells (alefacept) or TNF-alpha (etanercept, adalimumab and 
infliximab) or interleukin IL-12/IL-23 (ustekinumab)--their efficacy, safety, 
patient monitoring and recommended dosage. The purpose of the treatment 
guidelines presented here is to provide a high standard of continuing care of 
psoriasis and psoriatic arthritis patients.