Onychodermal Band

Figure 7.1

Leukonychia—hereditary type.

Subtotal leukonychia

In subtotal leukonychia there is a pink arc of about 2-4 mm in width distal to the white area. Nucleated cells in the distal area were believed to mature, lose their keratohyalin granules and then produce normal nail keratin several months after their formation. It was also suggested that parakeratotic cells are present along the whole length of the nail; these decrease in number as they approach the distal end, thus producing the normal pink colour up to the point of separation from the nail bed. There might, however, be sufficient nucleated onychocytes remaining for the nail to acquire a whitish tint after loss of contact with the nail bed. Some authorities feel that subtotal leukonychia is a phase of total leukonychia based on the occurrence of both types in different members of one family and the simultaneous occurrence in one person. In addition, either type may be found alone in some individuals at different times.

Transverse leukonychia

One or several finger nails exhibit a band, usually transverse, 1-2 mm wide and often occurring at the same site in each nail (Figures 7.2, 7.3). Transverse leukonychia is almost always due to trauma affecting the distal matrix, for example overzealous manicuring. The condition is more frequently seen in children and adolescents. There is apparently an inborn tendency to develop transverse leukonychia from minor repeated trauma.

Multiple transverse leukonychia may involve the great toes and/or the second toe nails. In these patients, whose nails are never trimmed short, the free margin is presumed to impinge on the distal part of the shoe. Cutting the affected nails short leads to complete cure.

Muehrcke Nails

Figure 7.2

Leukonychia—transverse banded type.

Figure 7.2

Leukonychia—transverse banded type.

Longitudinal Leukonychia

Figure 7.3

Extensive variant of the type in Figure 7.2.

Figure 7.3

Extensive variant of the type in Figure 7.2.

Punctate leukonychia

Punctate leukonychia is characterized by white spots 1-3 mm in diameter occurring singly or in groups almost exclusively on finger nails. They are usually due to repeated minor trauma to the matrix. The evolution of the spots is variable; appearing generally on contact with the cuticle, they grow distally with the nail. Approximately half of them disappear as they migrate towards the free edge. This is believed to prove that parakeratotic cells are capable of maturing and losing their keratohyalin granules to produce keratin, even though they have been without a blood supply for many months. Some white spots enlarge, while others appear at a distance from the lunula, suggesting that the nail bed is participating by incorporating groups of nucleated cells into the nail. A similar process could explain the exclusively distal leukonychia which is occasionally seen. A local or general fault in keratinization is not the only cause of punctate leukonychia; infiltration of air, which is known to occur in cutaneous parakeratoses, was for a long time believed to play a part. Disturbance of the nail plate's highly organized keratin fibre system alters its transparency and makes it look white. This is evidenced by polarization microscopy, as most clinically white spots lose their birefringence.

Leukonychia variegata Leukonychia variegata consists of white, irregular, transverse, thread-like streaks.

Isolated longitudinal leukonychia

Isolated longitudinal leukonychia is an example of localized metaplasia. It is characterized by a permanent, greyish-white longitudinal streak, 1 mm wide, below the nail plate. Histologically there is a mound of horny cells causing the white discoloration due to a lack of transparency, leading to alteration in light diffraction. Subungual filamentous tumour is the most common cause. Imbibition of blood may turn distal parts brown or even black.

Apparent leukonychia

The cause of apparent leukonychia is an alteration of the subungual tissue, either a vascular abnormality or onycholysis/nail bed hyperkeratosis.

White opacity of the nails in patients with cirrhosis is also called Terry's nails. In the majority of cases, the nails are of an opaque white colour, obscuring the lunula (Figure

7.4). This discoloration, which stops suddenly 1-2 mm from the distal edge of the nail, leaves a pink area corresponding to the onychodermal band. It lies parallel to the distal part of the nail bed and may be irregular. The condition involves all nails evenly.

A variation of Terry's nail is the Morey and Burke type in which the whitening of the nail extends to the central segment with a curved leading edge. Muehrcke's lines (Figure

7.5), which are mainly seen in hypoalbuminaemia, run parallel to the lunula and are separated from one another and from the lunula, by stripes of pink nail. They disappear when the serum albumin level returns to normal and reappear if it falls again. It is possible that hypoalbuminaemia produces oedema of the connective tissue in front of the lunula just below the epidermis of the nail bed, changing the compact arrangement of the collagen in this area to a looser texture, resembling the structure of the lunula; hence the whitish colour. The direct correlation between the presence or disappearance of the white bands and the serum

Onychodermal Band

Figure 7.4

Leukonychia (apparent) due to onycholysis.

Figure 7.4

Leukonychia (apparent) due to onycholysis.

Muehrcke Lines

Figure 7.5

White bands due to hypoalbuminaemia (Muehrcke's lines).

Figure 7.5

White bands due to hypoalbuminaemia (Muehrcke's lines).

albumin level appears to confirm this hypothesis. However, white finger nails preceded by multiple transverse white bands have been reported with normal serum albumin levels. Muehrcke's lines are common in patients undergoing systemic chemotherapy.

The uraemic half-and-half nail of Lindsay (Figure 7.6) consists of two parts separated more or less transversely by a well-defined line. The proximal area is dull white, resembling ground glass and obscuring the lunula; the distal area is pink, reddish or brown, and occupies between 20% and 60% of the total length of the nail (average 33%). In typical cases the diagnosis presents no difficulty, but in Terry's nail the pink, distal area may occupy up to 50% of the length of the nail; under these circumstances the two types may be confused. Half-and-half nail may display a normal proximal half, the colour of the distal part being due to an increase in the number of capillaries and thickening of their walls, or melanin granules in the nail bed. Sometimes the distinctly abnormal onychodermal band extends approximately 20-25% from the distal

Onychodermal Band

Figure 7.6

Uraemic half-and-half nail of Lindsay.

Figure 7.6

Uraemic half-and-half nail of Lindsay.

portion of the finger nail as a distal crescent of pigmentation with pigment throughout the brown arc of the nail plate.

Nail changes similar to those reported by Terry, Lindsay and Muehrcke have been termed 'Neapolitan nails'; they are probably simply a phenomenon of old age in otherwise normal individuals.

Anaemia may produce pallor of the nail (apparent leukonychia), if the haemoglobin level falls sufficiently, similar to mucous membrane and conjunctival pallor.

Dermatoses causing leukonychia

All conditions leading to onycholysis also cause apparent leukonychia. Psoriasis may cause both true and apparent leukonychia. True leukonychia is due to matrix involvement, and apparent leukonychia to onycholysis and/or parakeratosis of the nail bed. One of the earliest signs of leprosy is apparent macrolunula, which may become total in dystrophic leprosy.

Hailey Hailey Disease

Figure 7.7

Longitudinal white lines in Hailey-Hailey disease. (Courtesy of S.Burge, UK.)

Figure 7.7

Longitudinal white lines in Hailey-Hailey disease. (Courtesy of S.Burge, UK.)

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Responses

  • wegahta
    What causes onychodermal bands?
    6 years ago
  • christine whitson
    Is onychodermal band part of the nailbed?
    2 years ago
  • JUHO PAJU
    How to tell if the onychodermal band is healthy?
    9 months ago
  • liberty
    How to reshape the onychodermal band?
    7 months ago

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