This may be due to:
• Hyperkeratosis—psoriasis; fungal infection
• Hypertrophy—chronic trauma (onychogryphosis); pachyonychia congenita
• Atrophy lupus erythematosus—lichen planus; congenital dystrophy.
Thickening of the nail plate may be due to hyperkeratosis in psoriasis, in which case the changes will be symmetrical and there may well also be pitting of the nail and onycholysis. Similar changes are seen in fungal infection of the nail, which may be symmetrical on the toes. Nail clippings should be sent for microscopy and mycological culture.
Hypertrophy of the nail plate occurs as a result of chronic trauma, with only a few nails affected, and is usually seen in the feet.
Pachyonychia congenita is a rare congenital disorder characterised by hypertrophic nails.
Hyperkeratosis, due to the accumulation of keratin under the nail plate, is also seen in psoriasis. It occurs occasionally in association with chronic dermatitis.
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