Download The nails

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DERMATOLOGY
The nails
The hard keratin of nail plate is formed in nail matrix, which lies in an invagination
of the epidermis (the nail fold) on the back of the terminal phalanx of each digit. The
matrix runs from the proximal end of the floor of the nail fold to the distal margin of
lunule. From this area the nail plate grows forward over the nail bed, ending in a free
margin at the tip of the digit. Longitudinal ridges and grooves on the under surface of
the nail plate dovetail with similar ones on the upper surface of the nail bed.The nail
bed is capable of producing small amounts of keratin which contribute to the nail and
which are responsible for the ‘false nail’. The cuticle acts as a seal to protect the
potential space of the nail fold from chemicals and from infection. The nails provide
strength and protection for the terminal phalanx. They help with fine touch and with
the handling of small objects. The rate at which nails grow varies from person to
person: finger nails average between 0.5 and 1.2 mm per week, while toe nails grow
more slowly. Nails grow faster in the summer, if they are bitten, and in youth.They
change with ageing from the thin, occasionally spooned nails of early childhood to the
duller, paler and more opaque nails of the very old. Longitudinal ridging and beading
are common in the elderly.
►Effects of trauma: Permanent ridges or splits in the nail plate follow damage to
the nail matrix. Splinter haemorrhages the linear nature of which is determined by
longitudinal ridges and grooves in the nail bed,are mostly seen under the nails of
manual workers and are caused by minor trauma, psoriasis and of subacute bacterial
endocarditis. Larger subungual haematomas are caused by trauma .Chronic trauma
from sport and from ill-fitting shoes contributes to haemorrhage under the nails of big
toes, to the gross thickening of toenails known as onychogryphosis and to ingrowing
nails. Onycholysis, a separation of the nail plate from the nail bed a result of minor
trauma. nail psoriasis and in thyroid disease. The space created colonized by
yeasts,or by bacteria such as Pseudomonas aeruginosa, which turns it an ugly green
colour. Some nervous habits damage the nails. Bitten nails are short and irregular;
some people also bite their cuticles and the skin around nails. Viral warts can be seen.
In the common habit tic nail dystrophy, the cuticle of the thumbnail is the target for
picking or rubbing. This repetitive trauma causes a ladder pattern of transverse ridges
and grooves to run up the centre of the nail plate Lamellar splitting of the distal part
of the fingernails in housewives, attributed to repeated wetting and drying .Attempts
to beautify nails can lead to contact allergy. Culprits include the acrylate adhesive
used with artificial nails and formaldehyde in nail hardeners. contact dermatitis
caused by allergens in nail polish seldom affects the fingers but presents as small
itchy eczematous areas where the nail plates rest against the skin during sleep. The
eyelids, face and neck are favourite sites.
►Systemic disease:The nails can provide useful clues for general physicians.
Clubbing is a bulbous enlargement of the terminal phalanx with an increase in the
angle between the nail plate and the proximal fold to over180. It occur in chronic lung
disease , cyanotic heart disease, familial. The mechanisms un known. Koilonychia, a
spooning and thinning of the nail plate, indicates IDA.Colour changes: the ‘half-and-
half’ nail, with a white proximal and red or brown distal half in chronic renal
failure.Whitening of the nail plates in hypoalbuminaemia,as in cirrhosis of the liver.
Some drugs, antimalarials, antibiotics and phenothiazines,can discolour the
nails.Beau’s lines are transverse grooves which appear on all nails a few weeks after
an acute illness, and which grow steadily to the free margin.Connective tissue
disorders: nail fold telangiectasia or erythema in dermatomyositis, systemic sclerosis
and SLE. In dermatomyositis the cuticles shaggy, and in systemic sclerosis loss of
finger pulp leads to overcurvature of the nail plates.Thin nails, longitudinal ridging
and partial onycholysis,are seen if the peripheral circulation is impaired,in
Raynaud’s phenomenon.Nail changes in the common dermatoses:Psoriasis Most
patients with psoriasis have nail changes; severe nail involvement is more in presence
of arthritis.nail pitting of the surface of the nail plate. Almost as common is psoriasis
under the nail plate, showing up as red or brown areas, with onycholysis bordered by
obvious discoloration.There is no effective treatment for nails psoriasis. Eczema:
nails are polished by scratching.,eczema of the nail folds may lead to a coarse
irregularity with transverse ridging of the adjacent nail plates. Lichen planus 10% of
patients have nail changes.(thinning of the nail plate with irregular longitudinal
grooves and ridges , pterygium in which the cuticle grows forward over the base of
the nail and attaches itself to the nailplate) /Alopecia areata if severe roughness or
fine pitting of nail plates and the lunulae mottled. Infections: Acute paronychia The
portal of entry for the organisms( staphylococci), is a break in the skin or cuticle as a
result of minor trauma.The acute inflammation,with pus formation in nail fold or
under the nail, requires systemic flucloxacillin or erythromycin and surgical drainage.
Chronic paronychia a mixture of opportunistic pathogens (yeasts, Gram-+ve cocci
and Gram-ve rods) colonize the space between the nail fold and nail plate.
Predisposing factors ( poor peripheral circulation, wet work, working with flour,
diabetes, vaginal candidosis and over vigorous cutting back of the cuticles.nail folds
become tender and swollen, pus discharge. The cuticular seal is damaged and the
adjacent nail plate becomes ridged and discoloured. it may last for years. DDX:In
atypical cases, consider the outside chance of an amelanotic melanoma.in
dermatophyte infection the nail folds are not primarily affected.Investigations Test the
urine for sugar, check for vaginal candidosis. Pus should be cultured.
Treatment Manicuring of the cuticle should cease. The hands should be kept warm
and dry, and the damaged nail folds packed several times a day with an imidazole
cream and if swabs confirm candida, a 2-week course of itraconazole .
► Dermatophyte infections The common dermatophytes that cause tinea pedis
can invade the nails. Presentation Toenail infection is common and associated with
tinea pedis. The early changes occur at the free edge of the nail and spread
proximally. The nail plate yellow, crumbly and thickened. Usually only a few nails
are infected or all are. The fingernails are involved less often and the changes,in
contrast to those of psoriasis, are usually in one hand.it seldom clears
spontaneously.DDX Psoriasis.Yeast infections. Coexisting tinea pedis favours
dermatophyte infection of nail.
IX. Microscopic examination of a nail clipping. Cultures in a mycology laboratory.
►Tumours. Peri-ungual warts are common,stubborn. Cryotherapy must be used
carefully to avoid damage to nail matrix. It is painful but effective. Peri-ungual
fibromas from nail folds, in childhood, in patients with tuberous sclerosis. Glomus
tumours beneath the nail plate.The small red or bluish lesions are exquisitely painful
if touched and when the temperature changes. Treatment is surgical.Subungual
exostoses protrude painfully under the nail plate secondary to trauma to terminal
phalanx, the bony abnormality seen on X-ray and treatment is surgical. Myxoid cysts
occur on the proximal nail folds, usually of the fingers. The smooth domed swelling
contains a clear jelly-like material transilluminates well. A groove may form on the
adjacent nail plate. Cryotherapy, injections of triamcinolone and surgical excision.
Malignant melanoma should be suspected in any subungual pigmented lesion,
particularly if the pigment spreads to the surrounding skin. Subungual haematomas
may cause confusion but ‘grow out’ with the nail. The risk of misdiagnosis is highest
with an amelanotic melanoma, which may mimic chronic paronychia or a pyogenic
granuloma.
► Other abnormalities: congenital nails missing. In the rare nail–patella
syndrome, the thumb nails, and to a lesser extent those of the fingers, are smaller
than normal. Rudimentary patellae, and renal disease iliac spines complete the
syndrome, which is inherited as an AD trait linked with the locus controlling ABO
blood groups. Pachyonychia congenita is also rare and inherited as an AD trait. The
nails are grossly thickened, and have a curious triangular profile . Hyperkeratosis may
occur on areas of friction on the legs and feet. Permanent loss of the nails in the
dystrophic types of epidermolysis bullosa. In the yellow nail syndrome the nail
changes begin in adult life, against a background of hypoplasia of lymphatic system.
Peripheral oedema and pleural effusions may occur.The nails grow very slowly and
become thickened and greenish-yellow; their surface is smooth but they are
overcurved from side to side. The nail ‘en racquette’ is a short broad nail usually a
thumbnail, which is seen in some 1–2% of the population and inherited as AD trait.
The basic abnormality is shortness of the terminal phalanx.