DISORDERS OF NAILS:

Nail pitting can be caused by psoriasis, alopecia areata and atopic eczema. A few pits can be present because of trauma.
Onycholysis (distal nail plate separation) is caused by psoriasis, thyrotoxicosis, following trauma and rarely due to a photosensitive reaction to drugs such as tetracyclines.

Koilonychia (thin spoon-shaped nails) can be caused by iron deficiency anaemia or rarely is congenital.

Leuconychia (white nails) is seen in hypoalbuminaemia. A striate congenital leuconychia exists.

Beau's lines (transverse lines) appear as solitary depressions which grow out slowly over many months. They arise due to a severe illness or shock which causes a temporary arrest in nail growth.

Yellow-nail syndrome is a rare disorder of lymphatic drainage. It presents with thickened, slow-growing, yellow nails with associated pleural effusions, bronchiectasis and lymphoedema of the legs.

Onychogryphosis is a gross thickening of the nail which is seen in later life especially in the big toe-nail. There is often a history of preceding trauma. Both psoriasis and fungal infection can also cause nail thickening.

Nail-patella syndrome is an autosomal dominant condition which presents with triangular rather than half-moon-shaped lunulae, especially of the thumb and forefingers. The nail plates may be small or dystrophic. The patellae are hypoplastic or absent. Other skeletal anomalies can be present and renal impairment (glomerulonephritis) occurs in up to 30% of individuals.

Melanonychia (longitudinal brown streaks) are seen as a normal variant in black-skinned patients. In a white patient it may reflect an underlying subungual melanoma, especially if the pigmentation progresses proximally onto the nail fold ('Hutchinson's sign').

Clubbing is discussed on page 884.



FURTHER READING

Baran R, Dawber RPR (eds.) (2001) Diseases of the Nails and their Management, 3rd edn. Oxford: Blackwell Scientific Publications.