Dermatology Made Simple : Psoriasis : Definition Pathogenesis and Risk Factors

Psoriasis:

Psoriasis is a dermatological disease that has a variety of clinical types.

It has a genetic component and a number of exacerbating factors.

Nail changes and arthropathy may be associated in a number of cases.

Risk factors that can predispose to psoriasis include :

Hormonal Changes.

Stress

Infection

Pathogenesis:

Keratinocytes are skin cells that predominate in the epidermis,they grow from bottom/basal layer and slowly migrate to the surface.

In normal skin,this process of turnover usually takes 23 days.In patienst with psoriasis,cell turnover is rapidly accelerated taking only 3-5 days for cells to reach the surface and accumulate in large numbers.

This leads to one of characteristic features of psoriasis namely thickened skin due to scaling (hyperkeratosis).
Keratinocytes usually lose their nucleus as they move to the skin surface,In psoriasis however,they move so quickly that cell retain their nucleus throughout the epidermis.

Nail Involvement:

In a patient with psoriasis,nail involvement occurs and may have the following changes:

Onycholysis:

This means lifting of nail plate off the nail bed.

Sub-ungal hyperkeratosis:

Excessive proliferation of nail bed tissue.

Pitting:

Very small depressions in the nail plate.

Beau”s Lines:

Transverse lines on the nail plate.

Splinter haemorrhages:

Longitudinal black lines on nail