Psoriasis

•  Very common disease affecting about 1-2% of the U.S. population.
•  Pathogenesis poorly understood, with genetic, immunologic and environmental factors playing a role
•  Classic lesion is an erythematous plaque covered by silvery-white scale. May occur anywhere on body, but usually fairly symmetrical. Elbows, knees, lumbosacral area, gluteal cleft and scalp are favored areas.
  
•  Lesions often arise at sites of cutaneous trauma (Koebner phenomenon)
•  Typical pathology with hyperkeratosis, parakeratosis, acanthosis, elongated rete ridges, and collections of neutrophils in the upper part of the epidermis

•  Very common between ages 10-35
•  Infectious cause implicated, recently Herpesvirus type 7 suspected
•  May begin as a single “herald patch,” followed in days to weeks by oval, finely scaly, pink, 4-10 mm barely palpable papules. The herald patch does not always occur. Lesions most numerous on upper torso. May be slightly itchy. Patients usually otherwise well.


•  Resolves spontaneously in 4-12 weeks
•  Histology is that of a mild spongiotic dermatitis (eczema)

•  Inflammatory disease that can affect the skin, mucous membranes, hair and nails
•  Predilection for wrists, ankles and genitalia; very itchy!
• Small, flat-topped, polygonal, violaceous papules, sometimes with very fine, white, lacy lines on surface


• Characteristic pathology with destruction of the basal cell layer and a lymphocytic infiltrate just below the epidermis

•  Common form of hair loss affecting @ 1% of U.S. population
•  Most commonly presents as  small, circular patch of hair loss, but can become an extensive disease  causing loss of all body hair


•  Most cases of mild disease resolve spontaneously, but more severe disease can be resistant to even aggressive treatment
•  Histology shows miniaturization of hairs with a lymphocytic infiltrate surrounding the bulbs of some hairs