title: Methotrexate-induced papular eruption following treatment of psoriasis.
abstract: OBJECTIVE
  To report a case of a diffuse papular eruption following treatment of psoriasis with methotrexate injections.
  
  
  METHODS
  A 52-year-old woman presented with an extensive flare of psoriasis associated with joint pain, especially in her knees and elbows. She was treated with intramuscular injections of methotrexate 20 mg/wk. Ten hours after the second methotrexate injection, the patient experienced a diffuse pruritic papular eruption located mainly on the limbs. Histology showed foci of dyskeratosis in the mucosal layer and a polymorphic perivascular inflammatory infiltrate of the papillary dermis, suggesting a drug-induced skin reaction. According to the Naranjo probability scale, the papular eruption was probably caused by methotrexate. The drug was discontinued and papular lesions gradually disappeared.
  
  
  CONCLUSIONS
  Methotrexate-induced papular eruption is rarely reported shortly after beginning methotrexate therapy in patients with acute exacerbation of collagen vascular diseases. Methotrexate-induced papular eruption following treatment of psoriasis has not been previously reported.
  
  
  CONCLUSIONS
  The pathogenesis of methotrexate-induced papular eruption in collagen vascular diseases may suggest cutaneous small-vessel vasculitis. In our patient, histology showed aspects of drug-induced skin reaction without vasculitis. Pathogenesis of methotrexate-induced papular eruption in psoriasis may involve immune mechanisms other than those of methotrexate-induced cutaneous vasculitis in collagen vascular disease.
authors: Department of Dermatology, Farhat Hached Hospital, Sousse Tunisia.
authors: Amel
authors: A
authors: Mebazaa
authors: Nesrine
authors: N
authors: Kenani
authors: Mohamed
authors: M
authors: Denguezli
authors: Chaker
authors: C
authors: Ben Salem
authors: Sonia
authors: S
authors: Ziadi
authors: Badreddine
authors: B
authors: Sriha
authors: Colandane
authors: C
authors: Belajouza
authors: Rafiaa
authors: R
authors: Nouira
mesh_terms: D003875:Drug Eruptions / Q000209:etiology* / Q000473:pathology; D005260:Female; D006801:Humans; D007166:Immunosuppressive Agents / Q000009:adverse effects*; D007273:Injections, Intramuscular; D008727:Methotrexate / Q000009:adverse effects*; D008875:Middle Aged; D011537:Pruritus / Q000139:chemically induced / Q000473:pathology; D011565:Psoriasis / Q000188:drug therapy; D012867:Skin / Q000187:drug effects / Q000473:pathology; D012871:Skin Diseases / Q000139:chemically induced* / Q000473:pathology
chemical_list: D007166:Immunosuppressive Agents; D008727:Methotrexate