Local causes

Trauma (accidental, occupational, self-inflicted (Figure 4.6) or mixed) as with clawing, pinching or stabbing

Foreign bodies

Infection

Fungal

Bacterial

Viral (e.g. warts, herpes simplex, herpes zoster) Chemical irritants (accidental or occupational)

Prolonged immersion in (hot) water with alkalis and/or detergents, sodium hypochlorite, etc. Paint removers Sugar solution

Gasoline and similar solvents

Cosmetics (formaldehyde, false nails, depilatory products, nail polish removers);

nickel derived from metal pellets in nail varnish

Physical

Thermal injury (accidental or occupational) Microwaves are onychogryphosis and, in children, congenital malalignment of the hallux nails. In fungal onycholysis, primary Candida infection is almost exclusively confined to the finger nails. In distal subungual onychomycosis of the toe nails, the horny thickening raises the free edge with secondary disruption of the attachment of the nail plate to the nail bed. The nail bed epithelium is irreversibly transformed into epidermis, thus prohibiting reattachment of the nail.

Primary candidal onycholysis is almost exclusively confined to the finger nails. In distal subungual onychomycosis of the toe nails, the horny thickening raises the free edge of the nail with disruption of the normal nail plate-nail bed attachment: this gives rise to secondary onycholysis. Some authors have questioned whether great toe nail onychomycosis is ever truly primary. Its presence should always lead to a search for abnormalities of the foot such as hyperkeratosis of the metatarsal heads, thickening of the ball of the foot or pressure on the great toe by an overriding second toe.

Table 4.1 lists many potential causes of onycholysis. The most common types presenting to dermatologists are due to psoriasis, onychomycosis and the cosmetic 'sculptured' varieties of adult women.

ONYCHOMADESIS AND SHEDDING

Nails may be shed by the progression of any severe type of onycholysis causing the nail plate to separate more proximally (Figures 4.7-4.12). Onychomadesis is the spontaneous separation of the nail plate from the matrix area; this is associated with some arrest of nail growth (see the section on transverse lines, Chapter 3). At first a split appears under the proximal portion of the nail, followed by the disappearance of the juxtamatricial portion of the surface of the nail. A surface defect is thus formed, which does not usually involve the deeper layers. It is due to a 'limited' lesion of the proximal part of the matrix. In latent onychomadesis the nail plate shows a transverse split because of transient, complete inhibition of nail growth for a minimum of 1-2 weeks. It may be characterized by a Beau's line which has reached its maximum dimensions, although the nail continues growing for some time because there is no disruption in its attachment to the underlying tissues. Growth ceases when it is shed after losing this connection. In some severe, general acute diseases, such as Lyell's syndrome, the proximal edge of all the nail plates may be elevated. Growth proceeds because of the continued movement of the nail bed to which the nails remain attached (Figures 4.7-4.9).

The terms 'onychoptosis defluvium' or 'alopecia unguium' are sometimes used to describe traumatic nail loss. Onychomadesis usually results from serious generalized diseases, bullous dermatoses, drug reactions, intensive X-ray therapy, acute paronychia or severe psychological stress; or it may be idiopathic. Nail shedding may be an inherited disorder (as a dominant trait); the shedding may be periodic, and rarely associated with the dental condition amelogenesis imperfecta. Longitudinal fissures, recurrent onychomadesis and onychogryphosis can be associated with mild degrees of keratosis punctata. Minor traumatic episodes (as in 'sportsman's toe') may cause onychomadesis of the toe nails (Figure 4.12).

Retronychia has been described in patients with acute onychomadesis involving individuals with a 3-6 months' history of inflammation of the affected digits. After ineffective conservative treatment avulsion revealed three generations of nail joined distally but separated proximally, with the upper and oldest generation embedded into the overlying proximal nail fold. Failure of longitudinal growth, combined with the wedgelike effect of the new nail beneath, directed the overlying nail upwardsinto the proximal nail fold. This non-recurrent condition resolves through loss of the nail.

Total nail loss with scarring may be due to permanent damage of the matrix following trauma, or the late stages of acquired onychatrophy following lichen planus, bullous diseases or chronic peripheral vascular insufficiency. In texts on congenital anomalies this defect is sometimes referred to as aplastic anonychia, which does not always produce scarring, Temporary, total nail loss may also result from severe progressive onycholysis.

Peripheral Bullous Lesion Child

Figure 4.7

Lyell's syndrome—early proximal changes.

Figure 4.7

Lyell's syndrome—early proximal changes.

Retronychia

Figure 4.8

Lyell's syndrome—nail shedding. (Courtesy of S.Goettmann.)

Figure 4.8

Lyell's syndrome—nail shedding. (Courtesy of S.Goettmann.)

Congenital Anonychia

Figure 4.9

Lyell's syndrome—nails shed and permanent scarring. (Courtesy of S. Goettmann.)

Toenails Onychomadesis

Figure 4.10

Onychomadesis due to psoriasis.

Figure 4.10

Onychomadesis due to psoriasis.

Figure 4.11

Nail shedding due to pustular psoriasis.

Figure 4.12

Post-traumatic onychomadesis. Table 4.2 lists many of the recognized causes of nail shedding.

Figure 4.12

Post-traumatic onychomadesis. Table 4.2 lists many of the recognized causes of nail shedding.

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Responses

  • dahlak
    What causes tow nail shed?
    5 years ago

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