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INTRODUCTION

Nail diseases are often challenging to diagnose and manage. Non-specific nail changes such as onycholysis and pitting may be seen in many disparate entities, while a single medical condition like psoriasis, may present with multiple nail changes. The potential for permanent nail dystrophy resulting from nail matrix biopsies has also caused clinicians to be more reluctant in performing nail biopsies in doubtful cases. Therapy is often challenging as topical medications need to penetrate through the nail fold or nail plate to reach the nail matrix and nail bed, respectively, for effective treatment.

The nail matrix, which is situated under the proximal nail fold, is the site of production of the nail plate. Therefore, abnormalities of the nail matrix give rise to nail plate changes such as pitting, nail thickening, and Beau’s lines. Abnormalities in the nail bed may give rise to changes such as onycholysis, subungual hyperkeratosis, and apparent leukonychia. An understanding of the nail unit anatomy is essential in the interpretation of clinical signs, guiding the choice of biopsy site, as well as targeting treatment to the correct area.

NAIL CHANGES AFFECTING SPECIFIC AGE GROUPS

Nail changes affecting children

Some nail changes may be more commonly seen in children (Figures 20–1, 20–2, 20–3, 20–4, 20–5, 20–6). For example, trachyonychia of several or all fingernails and toenails in twenty-nail dystrophy with subsequent spontaneous resolution is seen almost exclusively in children (Figures 20–1 and 20–2). Congenital syndromes and genetic disorders such as ectodermal dysplasias may present with nail changes at birth or in childhood. Pachyonychia congenita (PC), a group of inherited conditions, present with marked nail bed hyperkeratosis in association with an increased transverse curvature of the nail plate (Figures 20–3, 20–4, 20–5). Some nail conditions such as childhood koilonychia, may be idiopathic and may resolve with time. Others such as pterygium inversus unguium, may persist into adulthood (Figure 20–6).

Figure 20-1

Trachyonychia

Trachyonychia refers to the longitudinal ridging and roughness affecting nails, resulting in a sand-papered texture. Apart from twenty-nail dystrophy as seen in this patient, trachyonychia may also be associated with psoriasis, lichen planus, or alopecia areata.

Figure 20-2

Twenty-nail dystrophy

Twenty-nail dystrophy describes trachyonychia that affects several or all fingernails and toenails. This condition most commonly affects young children and generally resolves spontaneously with age. No treatment is required.

Figure 20-3

Pachyonychia congenita type I

PC is an autosomal dominant condition with two main clinical subtypes: type 1 PC (Jadassohn-Lewandowsky) is more common and is due to a defect in keratins 6a and 16, while type 2 PC (Jackson-Lawler) is due to a defect in keratins 6b and 17. This ...

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