By Dr Ting Hoon Chin

TO understand nail diseases, it is necessary to have some knowledge of the structure of a normal nail. The components of a normal nail include:

1. Nail plate - This is the hard, translucent portion which is made of a fibrous protein called keratin. It provides a protective layer for the finger tip.

2. Nail bed - This is the skin beneath the nail plate.

3. Nail folds - The skin that frames the nail plate on the sides and base of the nail plate.

4. Lunula - The whitish half-moon part of the nail plate near the base.

5. Cuticle - The tissue that is situated between the base of the nail plate and the adjacent nail fold, fusing these structures and providing a water-proof barrier against external irritants.

6. Nail matrix - The nail grows from the nail root or matrix which is located under the base of the nail plate. As new cells grow, older cells become hard and compacted and are eventually pushed out towards the the finger tips.

Nail abnormalities may be a local disorder or part of a systemic disease. This article will highlight the more common and important abnormalities seen.

Nail changes in systemic diseases

Spoon-shaped nail

Spoon shaped nails with a concave surface (koilonychia) is a classic sign of iron deficiency anaemia. Rarely, it occurs as an occupational disorder, probably due to the softening of the nail with oils or alkali.

Beau's lines.

Beau's lines.

These appear as transverse ridges across the nail and is the result of temporary interference with nail growth. They may appear following infection such as mumps, measles and severe pneumonia or subsequent to a severe sudden disease like a heart attack.

Finger clubbing

Clubbed nail.

In clubbed nails, there is increased longitudinal or transverse nail curvature with thickening of the tissue between the nail fold and the nail. This is typically associated with congenital cyanotic heart diseases (certain 'hole in heart' conditions) and lung diseases (eg lung cancer and bronchiectasis). It may also occur with liver diseases (eg cirrhosis) and bowel diseases (eg ulcerative colitis).

Nail changes in skin disorders

Psoriasis

Nail changes in psoriasis.

In about half of psoriasis patients, the nails are abnormal. The commonest change is the appearance of little shallow pits in the nail, giving it a 'thimble' appearance. Onycholysis is the next most common change. This refers to the separation of an area of the nail from the nail bed, giving it a whitish colour. Between the whitish loosened area and the normally attached nail there is often a pinkish band. The third change is that of dystrophy, in which the nail is discoloured, roughened and sometimes greatly thickened. Psoriasis is the commonest skin disease to involve the nails.

Eczema

When the skin around the nails is affected by eczema, the nails can become abnormal as well. The usual change is that of irregular cross-ridging, but pitting (usually coarser than the pits seen in psoriasis) may also be seen.

Many other skin disorders like lichen planus, alopecia areata and Darrier's disease can cause nail changes, but they are less commonly seen.

Localised nail and nail bed disorders

Fungal infection

The nails can be attacked by the ringworm group of fungi. Non-ringworm fungi also attack the nails, but this is rather uncommon. The earliest sign is usually a white or yellowish patch at the outer free end or one side of the nail plate. Later, there can be thickening and ridging of the nail. Onycholysis may also be seen.

The changes can closely resemble the changes seen in psoriasis. However, unlike psoriasis, pitting is infrequently seen. In contrast with eczema, cross-ridging is not usually seen.

In case of uncertainty, it is easy to confirm the diagnosis of infection by a fungus through scraping the abnormal nail tissue, putting it into potassium hydroxide solution and examining it under the microscope to look for fungal filaments.

Fungus nail infections normally require treatment with oral drugs. The older drugs like griseofulvin need to be given for a long time to clear fungal nail infections (about six months for fingernails and about one year for toenails). Even then, there is quite a high failure rate. The new antifungals like itraconazole and terbinafine have better success rates and can be given for a shorter duration.

Chronic paronychia

This ranks in importance with psoriasis and fungal infection as a cause of nail disease. It is common in those who wet their hands regularly, eg domestic workers, housewives, cooks, hair stylists, fish mongers and canteen workers.

The condition begins as a slight swelling at the base of the nail, which is usually tender. The cuticle (the covering between the nail fold and the nail) is soon lost. Detergent and other solvents then get trapped in the space under the nail fold, causing irritation and inflammation, resulting in the nail fold becoming thick and swollen.

Later, yellowish discolouration, ridging and surface irregularities often occur in the nail. Infection by a yeast organism also plays a role in the development of this condition.

The most important aspect in the treatment of this condition is to keep the hands dry. Patients should wear gloves when they work. Topical treatment with liquids and cream containing anti-yeast agents should be used. To reduce chronic irritation and inflammation, a topical steroid may be added to the anti-yeast preparation.

Ingrown toenail

Ingrown toenail.

An ingrown nail is also a common nail condition in which the nail plate penetrates and grows into the tissue of the fold of skin on the sides of the nail, resulting in pain, swelling and secondary bacterial infection, sometimes with pus.

Ill-fitting footware together with inappropriate trimming of the nail are the causative factors. In the treatment of ingrown nail, the first step is to wear shoes that are wide and soft, to avoid pressure on the toes from the sides.

The nail must be allowed to grow till its edges are clear of the end of the toes before it is cut. The nails should be cut straight across rather than in a semicircle.

In the early stages, the infection may be overcome by the application of an antiseptic or antibiotic lotion or cream. A systemic antibiotic taken by mouth may be necessary if the infection is severe.

If the condition fails to respond to these conservative measures, partial removal of the nail and nail bed by surgery or the use of ablative lasers is usually curative.

Viral wart

Viral warts due to the papilloma virus can occur in the nail fold as well as under the nail. Involvement of the nail bed can cause ridging and deformity of the nail. Severe cases resemble a malignant growth, a bit like squamous cell carcinoma. Warts may recover spontaneously but often require treatment by topical salicylic ointment, freezing (cryotherapy) or surgical removal with carbon dioxide laser or curettage.

Abnormal pigmentation

A thin, long blackish strip called longitudinal melanonychia (LM) sometimes occurs in the nail. This is often due to pigmented naevus, which can be considered a form of benign mole.

This abnormality is more commonly seen in certain races, eg. Afro-Caribbeans, Mediterranean races and Asians. The problem is that early malignant melanoma, a type of cancer, is another possible cause of such a strip of black pigmentation. A biopsy may be necessary to exclude this cancer.

The chance of a malignant melanoma is higher if there is associated brown-black pigmentation around the nail, if the involved digit is a thumb or great toe and if the nail shows thickening or irregularities.

If melanoma is found, amputation of the finger or toe may be necessary.

This article is contributed by The Star Health & Ageing Panel, which comprises a group of panellists who are not just opinion leaders in their respective fields of medical expertise, but have wide experience in medical health education for the public. The members of the panel include: Datuk Prof Dr Tan Hui Meng, consultant urologist; Dr Yap Piang Kian, consultant endocrinologist; Datuk Dr Azhari Rosman, consultant cardiologist; A/Prof Dr Philip Poi, consultant geriatrician; Dr Hew Fen Lee, consultant endocrinologist; Prof Dr Low Wah Yun, psychologist; Datuk Dr Nor Ashikin Mokhtar, consultant obstetrician and gynaecologist; Dr Lee Moon Keen, consultant neurologist; Dr Ting Hoon Chin, consultant dermatologist; Prof Khoo Ee Ming, primary care physician; Dr Ng Soo Chin, consultant haematologist. For more information, e-mail starhealth@thestar.com.my. AsiaOne and The Star Health & Ageing Advisory Panel provide this information for educational and communication purposes only and it should not be construed as personal medical advice. Information published in this article is not intended to replace, supplant or augment a consultation with a health professional regarding the reader's own medical care. AsiaOne and The Star Health & Ageing Advisory Panel disclaim any and all liability for injury or other damages that could result from use of the information obtained from this article.

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-The Star/Asia News Network