INTRODUCTION
Psoriasis is a chronic, often lifelong inflammatory skin disease
that affects as many as 7.5 million Americans and
125 million people worldwide.1 Traditional treatments,
such as topical applications, phototherapy, methotrexate, and
cyclosporine have the potential to be ineffective, inconvenient
or toxic after long-term use.2 Improvements in the understanding
of the pathogenesis of psoriasis have allowed for the development
of treatment strategies that act on specific components
of the immune system.2 As tumor necrosis factor-α
(TNF-α
)
plays a key role in the etiopathogenesis of psoriasis, anti-TNF-α
biologic agents are now used increasingly as an effective, longterm
treatment of psoriasis.3
However, there have been some concerns regarding the safety
of anti-TNF-α
agents. Anti-TNF-α
agents have recently been reported
to induce thrombocytopenia. Reports of this adverse
event had been sporadic until a retrospective, observational
study of 93 patients by Brunasso et al. reported a 5.97 percent
(4 of 67 patients, 95% CI, 0% to 8.59%) rate of thrombocytopenia
occurrence among their cohort of patients receiving anti-TNF-α
agents for psoriasis and psoriatic arthritis.4
The anti-TNF-α
biologic drugs that are currently approved by the
U.S. Food and Drug Administration (FDA) include three agents
that are unique in structure, development and mechanism.
Etanercept is a recombinant human TNF-α
receptor protein
fused with the FC portion of IgG1 and adalimumab is a fully
human anti-TNF-α
monoclonal antibody.2 Infliximab is a chimeric
mouse-derived monoclonal IgG1 antibody with human
constant and murine variable components.5
A fourth biologic agent not of the anti-TNF-α
class, efalizumab,
was also included in the study by Brunasso et al. It is a recombinant
monoclonal antibody targeting the CD11a subunit of the
lymphocyte function-associated antigen 1 (LFA-1) integrin that
mediates T-cell adhesion.2 Efalizumab was withdrawn from the
worldwide market in 2009 due to reports of progressive multifocal
leukoencephalopathy in long-term users of the drug.
The present study was conducted to evaluate the frequency of
thrombocytopenia among psoriasis patients treated with any
of the three anti-TNF-α
agents. We sought to expand on the
findings by Brunasso et al. and to substantiate or refute the
reported rate of thrombocytopenia related to the use of anti-
TNF-α drugs for psoriasis in a larger patient group.
METHODS
A retrospective chart review was performed of 187 psoriatic patients
(male:female=93:94; mean age 47; median age 40; range
18–76) treated with anti-TNF-α
agents at the Adult Dermatology
Clinic, Baylor College of Medicine, Houston, Texas during the
period from December 2000 to November 2009.
Among all patients, 143 had received adalimumab, 81 had received
infliximab, and 43 had received etanercept. Of the 187
patients, 126 had received only one anti-TNF-α
agent, 47 had
received two anti-TNF-α
agents, and 14 had received all three
anti-TNF-α
agents over the course of their treatment. Thirteen
