'Max Joseph space' is a histopathological feature of?

Ans. B Lichen planus. (Ref. Rook's dermatology7th/ 42.3)Histological features of Lichen planus (LP)# The earliest finding is an increase in epidermal Langerhans' cells, associated with a superficial perivascular infiltrate of lymphocytes and histiocytes, impinging on the dermal-epidermal junction (DEJ).# A focal increase in thickness of the granular layer and infiltrate corresponds to the Wickham's striae.0# Degenerating basal epidermal cells are transformed into colloid bodies (appear singly or in clumps).0# The rete ridges may appear flattened or effaced ('saw-tooth ' appearance).# Focal separation from the dermis may lead Max Joseph spaces.Q# In 'active' LP, band-like infiltrate of lymphocytes and histiocytes, rarely with plasma cells, obliterates DEJ.# Epidermal melanocytes are absent or considerably decreased in number, while pigmentary incontinence with dermal melanophages is characteristic.Histopathology of psoriasis# Hyperkeratosis# Parakeratosis (involves startum corneum)# Thinning / absence of stratum granulosum# Munromicro abscess in parakeratotic startum corneum# Spongiform pustules of kagoj in St. malpighi# Dilated and tortous papillary capillaries with thinning of supra paillary epidermal plates.