Other Immune-Mediated Dermatosis (Lichen Planus, Erythema Multiforme, Toxic Epidermal Necrolysis, Graft-Versus-Host Reaction)

There are several immune-mediated lichenoid/interface dermatoses, with peculiar clinical-pathological findings and a wide range of severity. Occasionally, they can present with some overlap findings that can lead to a challenging differential diagnosis. Lichen planus is a common idiopathic inflammatory disease characterized by intensely itchy, polygonal, violaceous papules. Erythema multiforme is a self-limiting mucocutaneous reaction marked by targetoid lesions that typically affect acro-facial sites, often occurring after infection with the herpes simplex virus. Stevens-Johnson syndrome and toxic epidermal necrolysis are two rare and potentially life-threatening severe cutaneous adverse drug reactions. Graft-versus-host disease is a multi-organ disorder resulting from the transfer of foreign donor hematopoietic stem cells into a host through an allogeneic bone marrow transplant, posing a significant risk of morbidity and mortality in hematological patients. In all cases, a thorough physical examination is crucial, and in many instances, a skin biopsy demonstrating the lichenoid or interface dermatitis is necessary for diagnostic confirmation.