Some other nail abnormalities
A few people are born with one or more nails missing. In addition there are many conditions, either inherited or associated with chromosomal abnormalities and usually rare, in which nail changes form a minor part of the clinical picture. Most cannot be dealt with here.
In the rare nail–patella syndrome, the thumbnails, and to a lesser extent those of the fingers, are smaller than normal. Rudimentary patellae, and renal disease iliac spines complete the syndrome, which is inherited as an autosomal dominant trait linked with the locus controlling ABO blood groups.
Pachyonychia congenita is also rare and inheritedas an autosomal dominant trait. The nails are grossly thickened, especially peripherally, and have a curious triangular profile (Fig. 13.22). Hyperkeratosis may occur on areas of friction on the legs and feet.
Permanent loss of the nails may be seen with the dystrophic types of epidermolysis bullosa.
In the yellow nail syndrome (Fig. 13.30) the nail changes begin in adult life, against a background of hypoplasia of the lymphatic system.
Peripheral oedema is usually present and pleural effusions may occur. The nails grow very slowly and become thickened and greenish-yellow; their surface is smooth but they are overcurved from side to side.
The nail ‘en racquette’ is a short broad nail(Fig. 13.16), usually a thumbnail, which is seen in some 1–2% of the population and inherited as an autosomal dominant trait. The basic abnormality is shortness of the underlying terminal phalanx.