Many changes are characteristic for psoriasis:
Hyperkeratosis, which refers to increased thickness of the stratum corneum.
Parakeratosis is the phenomenon where the cell of the stratum corneum have nuclei (they usually lose their nuclei).
Neutrophilic microabscesses are focal accumulation of neutrophil remnants in the stratum corneum. (don’t mix these with parakeratosis)
The epidermis has lost its stratum granulosum.
There is acanthosis, which refers to increased thickness of the epidermis. It is equal to epidermal hyperplasia.
The dermal papillae are elongated and penetrate long into the epidermis.
Lymphoplasmocytic inflammatory foci are present in the dermis.
- Mechanical irritation
- Genetic predisposition
- Bacterial upper respiratory tract infection
Psoriasis can be diagnosed clinically by the Auspitz sign. When the scaly plaques are scraped off small pinpoint bleedings will appear underneath. This is because of the elongated dermal papillae. When the scale is ripped of the thin epidermis above the dermal papillae is ripped off too, which damages the arteries of the dermal papillae, causing these pinpoint bleedings.
47. Bullous pemphigoid
49. Giant cell tumor of bone (osteoclastoma)