1. Take a full history
Important things to ask about include:
- Occupation and hobbies – in particular if any of these have led to trauma to nails/wet work /exposure to irritant chemicals at work.
- Do they have manicures, pick and chew at the cuticle, or wear false nails?
- Do they suffer from any skin disease e.g. eczema, psoriasis, alopecia areata or suffer from any systemic disease (hyperthyroidism causes onycholysis).
- Do not forget to ask how their condition affects them.
2. Remember a thorough examination may well extend beyond the nails
A full examination involves the skin and a general assessment that may well extend beyond the nails – especially to the skin and sometimes to other systems such as the heart and lungs. Examine all the nails and the skin, teeth and mouth. A magnifying glass or dermatoscope can be useful here. If only the fingernails are affected think of contact dermatitis to nail polish or artificial nails. If only toenails are affected think of fungal infections or trauma from ill-fitting shoes.
Check for symmetrical abnormalities of nails – think of endogenous conditions like psoriasis, eczema and lichen planus. Look for evidence elsewhere – in the mouth, flexures, extensor aspects and scalp.
Look at the skin adjacent to the nail – nail dystrophy occurs with chronic paronychia due to chronic eczema and treating the eczema will treat the nail dystrophy.
3. Nail care advice is more important than a prescription for onycholytic nails
Separation of the nail plate from the bed can be due to a variety of causes:
- Long nails – secondary to chronic lifting of nail from nail bed during normal activity
- Psoriasis
- Photo-onycholysis (drugs eg naladixic acid or tetracyclines)
- Allergic contact dermatitis eg acrylic nails, polish
- Systemic causes eg thyrotoxicosis, pregnancy
- Fungal infections
- Trauma – usually great toe.
Offering advice is more useful in this case. You can trim the nail back as far as possible to prevent lifting and to keep subungual area as dry as possible, but advise the patient not to clean beneath the nail as this exacerbates the condition. They should keep hands out of water as much as possible and dry thoroughly after washing and use emollients.
Pseudomonas colonises onycholytic nails, producing a characteristic greenish black colour. Treat by keeping the area dry and using acetic acid soaks – the cheapest option is to get the patient to apply vinegar under nail, and it has fewer side effects than systemic therapy.
4. Do not treat onychomycosis without taking nail clippings for microscopy
Nail dystrophy is very common, especially in the elderly, but not all is due to onychomycosis, which is most commonly caused by dermatophytes and occasionally yeasts. It can be difficult to diagnose in thickened nails.
It is important to take nail clippings – try to obtain the crumbly soft subungual material to improve culture rate – and start treatment only after results are known. Fungal culture has low sensitivity so negative results should result in repeat culture if fungal infection is clinically likely (e.g. in presence of diabetes). Yeasts or moulds cultured from non-thickened nails may be commensals and do NOT require treatment. Topical agents are generally ineffective and oral agents should be used for at least two months for fingernails and three months for toenails.
5. Curing chronic paronychia can take a long time
Chronic paronychia is characterised by redness, swelling and inflammation of periungual areas. The cuticle which acts as a seal is destroyed and significant nail dystrophy occurs.
Causes include:
- Physical damage – manicures and pushing back the cuticle
- Wet work – laundry and bar work
- Chronic colonisation with candida and bacteria.
- Eczemas such as irritant and allergic contact dermatitis (solvents, detergents, saliva, nail polish and artificial nails).
Treat eczema in the periungual area with topical steroid, emollient and allergen avoidance if relevant. Apply imidazole cream tds to destroy any candida. Importance of good hand care cannot be too highly emphasised. It takes time to reverse the changes and patients need to be warned of this.
6. Careful examination is especially important when there is pigmentation under nail
Pigmentation can be caused by subungual haematoma, melanoma or longitudinal melanonychia. To differentiate, subungual haematoma occurs acutely while that of melanoma does not.
Subungual haematoma is more likely to be blue or red with a smooth scalloped border. Look for haematoma under adjacent toenails. Melanoma usually involves skin of the digit or the lateral proximal nail fold (Hutchinson sign). Benign causes of longitudinal melanonychia have parallel edges whereas melanoma will tend to converge from the proximal nail fold to the free edge of the nail.
7. Leave digital mucous (myxoid) cysts alone unless they are very symptomatic
A digital mucous cyst is a translucent papule on the dorsal part of the digit. They communicate with the distal interphalangeal joint and if punctured clear viscous synovial fluid is released. They can cause grooving of nail plate if they are impinging on nail matrix.
The many treatments reflect the poor success rates - cryotherapy, intralesional steroid injection, aggressive curettage. I recommend that you leave them alone or refer to plastic surgeons if they are very symptomatic.
8. Antibiotics are only part of the management for ingrowing nails
Irritation of the lateral nail fold by the nail plate causes swelling, and this leads to a vicious cycle of production of granulation tissue and more swelling. Conservative treatment consists of oral antibiotics, regular warm soaks and cutting the nail straight across. If this fails, referral for wedge resection of ⅓ of the nail with phenolisation of the matrix to stop regrowth is appropriate.
9. Know where to look for signs of systemic skin disease affecting the nails
Psoriasis can induce pitting, salmon pink patches, ‘oil spots’ and onycholysis. Severe nail disease will require systemic therapy and often causes significant psychological distress. Alopecia areata causes nail pitting and observation of the nails can help with the diagnosis. Lichen planus can cause thinning, onycholysis and pterygium formation. Aggressive treatment (second-line agents) may be justified to prevent scarring.
Beau’s lines are transverse furrows due to the arrest of growth during systemic illness or chemotherapy. The lines may take six months to grow out in fingernails.
10. Have a low threshold for referral of subungual nodules
It is important to know the differential diagnosis: subungual exostosis, viral wart, squamous cell carcinoma, keratoacanthoma, melanoma or glomus tumour. If there is uncertainty about the diagnosis then consider biopsy. Diagnoses of SCCs are often delayed significantly.
Dr Andy Jordan is a locum GP and hospital practitioner in dermatology at Amersham Hospital, Buckinghamshire.
