Abstract
Background: Lichen planus is a dermatosis that occurs preferentially in middle-aged adults. Although its association with liver disease is widely documented, it remains a controversial subject with discordant results depending on the studies. We report a particular case of an eruptive lichen planus that revealed a recurrence of a hydatid cyst of the liver. Case report: 54-year-old man, operated on for a hydatid cyst of the liver 3 years ago. He presented 15 days before admission, a diffuse itchy rash with shiny flat violaceous polygonal papules, affecting the trunk, the upper and lower limbs. There was no mucosal or Phanerial involvement and the rest of the clinical examination were without particularity. The diagnosis of lichen planus was evoked and confirmed by a histological study. The biological assessment showed the presence of eosinophilia at 600 / mm3 and a minimal cholestasis. In front of this clinical and biological picture, we carried out a liver ultrasound completed by an abdominal computed tomography. They revealed the presence of a hydatid cyst type 3 of Gharbi. The diagnosis was confirmed by the positivity of the hydatid serology. The evolution was good with topical corticosteroids. The patient did not reoffend after three years. Discussion: The lichen planus is a frequent dermatosis of unknown etiology. His association with liver disease has been widely controversial. The data concerning the association with a parasitosis are even rarer, hence the interest of our observation. Indeed, it is a cutaneous manifestation nonspecific but never described, infection with Echinococcus granulosus. This is to our knowledge the first reported case of a lichen eruptive planus revealing this infection. This discovery allowed us to make an early diagnosis of a clinical situation that could lead to very serious and sometimes fatal complications. This could also alert us to the need for a minimal etiological balance in each case of eruptive lichen. Conclusion.: The lichen planus remains a mysterious dermatosis of unknown etiology, which involves immunological mechanisms not yet well understood. Extensive and wide-ranging studies are still needed for a better understanding of pathophysiological mechanisms and a broad understanding of the range of comorbidities that may be associated.

Key words: Lichen planus, Hydatid cyct, Comorbidities