Fragile Brittle And Soft Nails

Many of the nail diseases that disrupt nail formation and structure cause secondary brittleness and fragility. In this chapter only those conditions leading to nail fragility or brittleness as a major sign are considered in any detail (Figures 6.1-6.7).

'Hapalonychia' is the term used for cryptogenic soft nail—cases for which there is no primary specific local nail disease to explain the change. Diseases and conditions associated with this include:

congenital types sulphur deficiency syndromes

Figure 6.1

Distal nail fissure.

Figure 6.2

Distal nail fragility. Crenellated distal splitting associated with distal

Figure 6.2

Distal nail fragility. Crenellated distal splitting associated with distal

A text atlas of nail disorders 168 onycho-schizia (splitting into layers).

Figure 6.3

Surface nail fragility and fractures due to nail varnish (keratin granulations).

Figure 6.3

Surface nail fragility and fractures due to nail varnish (keratin granulations).

Figure 6.4

Nail fragility in lichen planus. (ridging, splitting and onychoschizia).

Figure 6.4

Nail fragility in lichen planus. (ridging, splitting and onychoschizia).

Figure 6.5

Severe nail plate fragility after etretinate therapy before loss.

Figure 6.5

Severe nail plate fragility after etretinate therapy before loss.

Figure 6.6

Nail apparatus—amyloidosis.

Figure 6.6

Nail apparatus—amyloidosis.

Figure 6.7

Darier's disease, with some nail plate loss.

Figure 6.7

Darier's disease, with some nail plate loss.

• thin nail plate of any cause

• occupational disease (for example working with industrial oils)

• chronic arthritis

• hypothyroidism

• peripheral ischaemia

• peripheral neuritis

• hemiplegia

• cachexic states.

In some cases of hapalonychia the thinned nails assumed a semi-transparent, bluish-white hue, sometimes described as 'eggshell nails'. Nail fragility syndrome can be divided into six main types on morphological grounds:

1 An isolated longitudinal split at the free edge which sometimes extends proximally.

2 This may result from onychorrhexis with shallow parallel furrows running on the superficial layer of the nail.

3 Multiple, crenellated splitting which resembles the battlements of a castle. Triangular pieces may easily be torn from the free margin.

4 Lamellar splitting of the free edge of the nail into horizontal fine layers (onychoschizia) (see Figures 3.39, 3.43). This may occur alone or associated with the other types.

5 Transverse splitting and breaking of the lateral edge close to the distal margin.

6 Nail friability is observed in psoriasis, onychomycosis and as adverse effect of nail varnish (keratin granulations, figure 6.3).

The changes in brittle, friable nails are often confined to the surface of the nail plate; this occurs in superficial white onychomycosis and may be seen after the application of nail polish or base coat which causes 'granulations' in the nail keratin. In advanced psoriasis and fungal infection the friability may extend throughout the entire nail.

The changes in nail consistency may be due to impairment of one or more of the factors on which the health of the nail depends, for example variations in the water content or keratin structure and corneocyte adhesion. In addition, changes in the intercellular structures and cell membranes, and intracellular changes in the arrangement of keratin fibrils, have been revealed by electron microscopy. Normal nails contain approximately 18% water. After prolonged immersion in water this percentage is increased and the nail becomes soft; this makes toe-nail trimming and nail biopsies much easier. A low lipid content may decrease the nail's ability to retain water. If the water content is considerably reduced, the nail becomes brittle. Splitting, which results from this brittle quality, is probably partly due to repeated uptake and rapid drying out.

The keratin content may be modified by chemical and physical insults, especially in occupational nail disorders. Amino acid chains may be broken or distorted by alkalis, oxidizing agents and thioglycollates (used in the permanent waving of hair). These break or distort the multiple disulphide bond linkages which join

Table 6.1 Factors leading to fragile, brittle or soft nails_

Local factors

Trauma Occupational Onychotillomania Chemical

Dermatological conditions (may thin the nail plate) Alopecia areata Amyloidosis Darier's disease Eczema Lichen planus Lichen striatus Onychomycosis Psoriasis Slow nail growth

General factors

Aging (fingers) Anaemia (iron deficiency) Cachexic state

Chronic arthropathies (fingers or toes) Drugs

Antimetabolites Arsenic

Acitretine (etretinate) Gold salts

Penicillamine

Vitamin A, C and B6 deficiencies Gout

Graft-versus-host disease

Haemodialysis

Hyper- or hypothyroidism

Neurological

Hemiplegia

Neuropathies

Osteomalacia

Osteoporosis

Peripheral circulatory impairment (arterial) Pregnancy

Sulphur deficiency diseases_

the protein chains to form the keratin fibrils. Keratin structure can also be changed in genetic disorders such as dyskeratosis congenita, in which the nail plate is completely absent or reduced to thin, dystrophic remnants. The composition of the nail plate is sometimes related to generalized disease. A high sulphur content, predominantly in the form of cystine, contributes to the stability of the fibrous protein by the formation of disulphide bonds. A lack of iron can result in softening of the nail and koilonychia; conversely, the calcium content of the nail appears to contribute little towards its hardness. Age-dependant decrease in cholesterol sulfate levels might explain the higher incidence of brittle nails in women. Calcium is located mainly in the surface of the nail, in small absorbed quantities, and X-ray diffraction shows no evidence of calcite or apatite crystals.

Damage to either the central or the peripheral nervous system may result in nail fragility.

Local causes

The nail may be damaged by repeated trauma or by chemical agents such as detergents, alkalis, various solvents, sugar solutions and especially by hot water. The nail plate takes a minimum of 5-6 months to regenerate and therefore it is vulnerable to daily insults. Housework is commonly the cause; particularly at risk are the first three fingers of the dominant hand. Anything that slows the rate of nail growth will increase the risk. Cosmetic causes are rare. Some varnishes will damage the superficial layers of the nail. Drying may be enhanced by some nail varnish removers. Soaking fingers in warm soapy solution, for removing the cuticle, is especially dangerous; this is common practice among manicurists. It has been shown that climatic and seasonal factors may affect the hydration of the nail plate.

Fragility, due to thinning of the nail plate, may be caused by a reduction in the length of the matrix. Diminution or even complete arrest of nail formation over a variable width may be the result of many dermatoses such as eczema, lichen planus, psoriasis (rare) and impairment of the peripheral circulation. The frequency of nail fragility in alopecia areata lends credence to the popular belief that nail and hair disorders are often associated.

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