Munro microabscesse are seen in

PSORIASIS. It usually appears first between the age of 15 and 30 years. The lesions are characterised by brownish-red papules and plaqueswhich are sharply demarcated and are covered with fine, silvery white scales. As the scales are removed by gentle scraping, fine bleeding points appear termed Auspitz sign. In about 25% of cases, peculiar pitting of nails is seen. Psoriatic ahritis resembling rheumatoid ahritis is produced in about 5% of cases but the rheumatoid factor is absent.Histologically, the following features are observed in fully-developed lesions.i) Acanthosis with regular down growth of rete ridges to almost the same dermal level with thickening of their lower poion.ii) Elongation and oedema of the dermal papillae with broadening of their tips. iii) Suprapapillary thinning of stratum Malpighi.iv) Absence of granular cell layer.v) Prominent parakeratosis.vi) Presence of Munro microabscesses in the parakeratotic horny layer is diagnostic of psoriasis. Ref: Harsh Mohan - Textbook of Pathology, 6th Edition.page no.778