Linear lesion is seen in -

Sporotrichosis : Is a subacute or chronic infection caused by sporothrix scheinkii characterised by nodular lesions and ulcers in the skin and subcutaneous tissue and lymph nodes with occasional involvement of internal organs. Etiology : Causative organism:sporothrix scheinkii Dimorphic fungus Mycelia at 26c- bearing flower head endings of mycelia Yeast at 37c Saprophyte in soil and dead plants Route of entry scratches thorn prick Histopathology: Asteroid bodies basphilic yeast like body surrounded by radiating homogeneous eosinophilic material surrounded by granulomatous reaction. Clinical features Lymphocutaneous sporotrichosis =Trauma followed by development of nodules and ulcers along the line of lymphatic stocks Mucocutaneous sporotrichosis Fixed cutaneous sporotrichosis Pulmonary sporotrichosis Disseminated sporotrichosis Laboratory diagnosis. Sabourauds dextrose agar culture Animal inoculation cigar bodies in pus from lesions Sporotrichin skin test Treatment: Treatment of choice for lymphocutaneous lesion: saturated solution of potassium iodide three drops tid Itraconazole Terbinafine Voriconazole Iadvl textbook of dermatology page 306 PSORIASIS:-Inflammatory skin disease.Genetic predisposition. Psoriasis susceptibility 1 (PSORS1) is the most impoant susceptibility locus. 1. Classic lesion-Well defined erythematous plaque with a silvery white scales.2. Size varies from pin point papules to plaques. LICHEN PLANUS:- Inflammatory T cell mediated auto immune disorder affecting skin, hair,nails and mucous membranes. Four Ps- purple , polygonal and pruritic papule. Classic lesion- small polygonal shaped, and red/ violet, flat topped papule. Surface is slightly shiny/ transparent,and a network of fine,white lines called 'Wickhams striae' or small grey white puncta is also seen.