Table 45 Causes of thick nails andor subungual hyperkeratosis Frequent

Onychomycosis (Figure 4.19) Psoriasis (Figures 4.14-4.15) Contact eczema Mineral oils Cement

Hair styling products Repeated microtrauma Single major trauma Subungual clavus Less frequent Bowen's disease Lichen planus (Figure 4.24) Norwegian scabies

Pachyonychia congenita (Figures 4.21-4.23)

Pityriasis rubra pilaris (Figure 4.20)

Acrokeratosis paraneoplastica (Bazex's syndrome)

Reiter's syndrome

Darier's disease (Figure 4.25)



Sezary's syndrome

Onychopapilloma of the nail bed Rare

Alopecia areata Radiodermatitis Arsenic keratosis


Splinter haemorrhages

The subungual epidermal ridges extend from the lunula distally to the hyponychium and fit 'tongue and groove' fashion between similarly arranged dermal ridges. The disruption of the fine capillaries along these longitudinal dermal ridges results in splinter haemorrhages (Figures 4.26-4.29).

Macroscopically, splinter haemorrhages appear as tiny linear structures, usually no more than 2-3 mm long, arranged in the longaxis of the nail. The majority originate within the distal third of the nail from the 'spirally wound' capillary which produces the pink line normally seen through the nail about 4 mm proximal to the tip of the finger. When splinter haemorrhages originate from the proximal portion of the nail accompanied by a longitudinal xanthonychia, the diagnosis of onychomatricoma should be considered. Splinter haemorrhages rarely involve the whole nail bed. When first formed they are plum-coloured but darken to brown or black within 1-2 days; subsequently they move superficially and distally with the growth of the nail, and at this stage they can be scraped from the undersurface of the nail plate. The nature of splinter haemorrhages is not clearly known. They may result from emboli in the terminal vessels of the nail bed; the emboli may be septic, or due to trauma of various types; they are more common in the first three fingers of both hands, and develop at the line of separation of the nail plate from the nail bed. Familial capillary fragility may cause splinter haemorrhages in otherwise healthy individuals. Occasional haemorrhages are of no clinical significance and are probably traumatic. There is a statistically greater incidence of splinter haemorrhages in men than in women, and in black compared with white individuals. In healthy women they are usually confined to a single digit. Histochemical studies of nail parings confirm that the linear discoloration is derived from blood. The blood pigments give a negative Prussian blue and Pearls' reaction.

Many conditions may be associated with splinter haemorrhages (Table 4.6). In all cases it is probable that, whatever the pathogenesis, the nail bed capillaries are more susceptible to minor trauma leading to linear haemorrhages.

Splinter Haemorrhages

Figure 4.26

Splinter haemorrhages.

Figure 4.26

Splinter haemorrhages.

Black Splinter Line Fingernails Picture

Figure 4.27

Psoriatic distal subungual splinter haemorrhages.

Figure 4.28

Sites of splinter haemorrhages in the nail bed.

Figure 4.28

Sites of splinter haemorrhages in the nail bed.

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    What causes a black line on fingernail?
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