Chapter 129

### Introduction

A physician should wear white garments, put on a pair of shoes, carry a stick and an umbrella in his hand, and walk about with a mild and benignant look as a friend of all created beings. He should be cleanly in his habits and well shaved, and should not allow his nails to grow.

Sushruta-Samhita (5th century BC)

Making a diagnosis of abnormal nails for a concerned patient can be quite simple for a few obvious conditions. However, in many cases the diagnosis can be elusive when we are not familiar with classic patterns that are seen so infrequently. The diagnostic process can be facilitated by learning the basic anatomy and function of the nail, as well as characteristic patterns, which are presented with the aid of diagrams in this chapter. There are, in fact, only a limited number of ways in which injury, infection and inflammation can present in a nail.1

The main nail problems encountered in general practice are trauma, onychomycosis, infection, ingrowing toenails, paronychia and psoriasis. Fungal nail infection and psoriasis are the commonest causes of nail dystrophy. Damage to the nail from trauma or disease results in nail dystrophy. The problem of nail changes due to onychotillomania, be it from excessive nail biting, picking or cleaning, should be suspected from the history and examination.

The examination should include a general inspection of the skin including in the webbing of the toes, looking for evidence of a skin disorder such as psoriasis, atopic eczema, lichen planus and tinea.

Key facts and checkpoints

• The growth rate of nails varies between individuals: fingernails average 0.5–1.2 mm per week while toenails grow more slowly.2

• An avulsed or totally dystrophic nail will take up to 9 months to regrow.

• It takes approximately 6 weeks to grow a new cuticle.

• Beau’s lines associated with a severe acute illness take about 3 months to appear.

• Do not confuse chronic paronychia with onychomycosis. The former affects the nail folds, the latter mainly affects the distal nail.

• Nail clippings for culture and histology may be the only way to differentiate between nail dystrophy and onychomycosis.

• Not all white crumbly nails are caused by a fungus.

• Suspect melanoma in any subungual pigmented lesion. Do not confuse with subungual haematomas, which ‘grow out’ with the nail. They usually present as a longitudinal pigmented streak. Beware of amelanotic melanoma, which may mimic chronic paronychia or a pyogenic granuloma.23 Any suspicion necessitates early referral.

• Various dermatoses and connective tissue disorders can affect the nails—psoriasis, lichen planus, lupus erythematosus, scleroderma, bullous pemphigoid, Darier disease (keratosis follicularis).4

• Clubbing of the fingers is basically an abnormality of the fingertips—look for evidence of major pulmonary or cardiac disease.

• Significantly bitten or traumatised nails may be a symptom of a major anxiety disorder—explore psychogenic issues.

A summary of causes of abnormal ...

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