Eruptive papules during efalizumab (anti-CD11a) therapy of psoriasis vulgaris: a case series.
BACKGROUND
Newer biological therapies for moderate-to-severe psoriasis are being used more frequently, but unexpected effects may occur.


METHODS
We present a group of 15 patients who developed inflammatory papules while on efalizumab therapy (Raptiva, Genentech Inc, anti-CD11a). Immunohistochemistry showed that there were increased CD11b+, CD11c+ and iNOS+ cells (myeloid leukocytes) in the papules, with relatively few CD3+ T cells. While efalizumab caused a decreased expression of CD11a on T cells, other circulating leukocytes from patients receiving this therapy often showed increased CD11b and CD11c. In the setting of an additional stimulus such as skin trauma, this may predispose to increased trafficking into the skin using these alternative beta2 integrins. In addition, there may be impaired immune synapse formation, limiting the development of these lesions to small papules. There is little evidence for these papular lesions being "allergic" in nature as there are few eosinophils on biopsy, and they respond to minimal or no therapy even if efalizumab is continued.


CONCLUSIONS
We hypothesize that these papules may represent a unique type of "mechanistic" inflammatory reaction, seen only in the context of drug-induced CD11a blockade, and not during the natural disease process.
Lowes
Michelle A
MA
Laboratory for Investigative Dermatology, The Rockefeller University, New York, New York, USA. jgk@rockefeller.edu.
Chamian
Francesca
F
Abello
Maria V
MV
Leonardi
Craig
C
Dummer
Wolfgang
W
Papp
Kim
K
Krueger
James G
JG
D000911:Antibodies, Monoclonal / Q000009:adverse effects* / Q000276:immunology / Q000627:therapeutic use; D061067:Antibodies, Monoclonal, Humanized; D040881:CD11a Antigen / Q000276:immunology / Q000378:metabolism; D039481:CD11b Antigen / Q000378:metabolism; D039521:CD11c Antigen / Q000378:metabolism; D017252:CD3 Complex / Q000378:metabolism; D003713:Dendritic Cells / Q000201:enzymology / Q000276:immunology / Q000473:pathology; D003875:Drug Eruptions / Q000201:enzymology / Q000209:etiology* / Q000276:immunology / Q000473:pathology; D006801:Humans; D007150:Immunohistochemistry; D007962:Leukocytes / Q000201:enzymology / Q000276:immunology; D052247:Nitric Oxide Synthase Type II / Q000378:metabolism; D011565:Psoriasis / Q000188:drug therapy*; D012867:Skin / Q000201:enzymology / Q000276:immunology / Q000473:pathology; D013601:T-Lymphocytes / Q000276:immunology / Q000473:pathology
D000911:Antibodies, Monoclonal; D061067:Antibodies, Monoclonal, Humanized; D040881:CD11a Antigen; D039481:CD11b Antigen; D039521:CD11c Antigen; D017252:CD3 Complex; D052247:Nitric Oxide Synthase Type II; C472181:efalizumab