Psoriasis in the nails can cause thimble pitting of the nails, accumulation of chalky scale under the nails or cause the nails to become detached from the nail bed. Psoriasis in the scalp is similar to psoriasis on the body but scaling is very variable and the plaques are hidden by the hair so the sufferer usually complains of scaling and lumps in the scalp. Erythrodermic psoriasis is where the whole body is red and has fine scaling over the surface. This is a serious event as the body loses heat and fluid from the skin and is more open to infection. Usually this occurs when treatment for psoriasis, particularly tablet treatment, is suddenly withdrawn.
Pustular psoriasis is where the areas of psoriasis are studded with small pustules.
This, like erythrodermic psoriasis is a serious condition and can arise because of sudden withdrawal of treatment or can be caused by certain treatments. The vast majority of patients with psoriasis can be treated by the GP with creams and lotions. The most useful are based on vitamin D but preparations containing tar and dithranol have their place. Tests for rheumatoid arthritis are negative but the arthritis can look like rheumatoid arthritis. There is no correlation between the extent or severity of the psoriasis and the severity of the arthritis.