Nail pitting is caused by all except -

Nail involvement is common in alopecia areata, paicularly in severe forms. Pitting is the most common finding, but other abnormalities such as trachyonychia have been repoed. Nail plate pitting tends to be more shallow and regularly spaced than in psori-atic nail pitting Nail pitting is often a sign of another condition that can include: psoriasis, which causes skin inflammation. reactive ahritis or inflammation caused by an infection elsewhere. alopecia areata, which causes temporary bald patches on the scalp. Ref Harrison20th edition pg 1278