[Trachyonychia: 20-nail dystrophy].

Trachyonychia (20-nail dystrophy) is described in four patients with clinical, histological, and scanning electron microscopy techniques. Trachyonychia is a polyetiological symptom: psoriasis vulgaris, lichen planus, alopecia areata, atopic dermatitis, 20-nail dystrophy of childhood, and severe nail dystrophy can all lead to trachyonychia-like nail changes. Nail bed biopsies are necessary for proper diagnosis. In our patients, lichen planus, or psoriasis were excluded clinically and histologically. Spongiotic dermatitis of nail matrix and nail bed with column-like parakeratosis within the nail plate are found in trachyonychia due to alopecia areata, atopic dermatitis, and in its idiopathic form.