The nails are at the end of each fingertip on the dorsal surface. The primary function of nails is protection, which also helps a firm grip for holding articles. It consists of a strong, relatively flexible keratinous nail plate originating from the nail matrix. Under the nail plate, there is a soft tissue called a nail bed. There is a nail fold or cuticle between the skin and the nail plate. A regular healthy nail is slightly pink, and the surface is convex from side to side. Fingernails grow 1 cm in three months, and toenails take 24 months.
Importance of nails in disease diagnosis:
The colour, appearance, shape and nature of the nails give information about a person’s general health and hygiene. Nails are examined as a routine by all doctors to get clues about underlying diseases. Just looking at nails, we can make out the hygiene of a person. The abnormal nail may be congenital or due to some diseases. The cause for changes in the nail extends from simple reasons to life-threatening conditions. Hence the examination by a doctor is essential for diagnosis.
Some abnormal findings with probable causes are discussed here for general awareness.
We can make out an unhygienic nail very quickly. Deposition of dirt under the distal end of the nail plate can create a chance for ingestion of pathogens while eating. If nails are not cut correctly, it can result in worm troubles in children. When the worms crawl in the anal orifice, children will scratch, which lodges the ova of worms under the nails and consumed while eating. Prominent nails can also complicate a skin disease by habitual scratching. Sharp nails in small kids cause minor wounds when they do foot kicking or hand waving.
2. Colour of the nails:
Nails become pale in anaemia.
Opaque white discolouration (leuconychia) occurs in chronic renal failure and nephrotic syndrome.
Whitening occurs in hypoalbuminaemia as in cirrhosis and kidney disorders.
Drugs like sulpha group, anti-malarial and antibiotics can produce discolouration in the nails.
Fungal infection causes black discolouration.
In pseudomonas infection, nails become black or green.
Nail bed infarction occurs in vasculitis, especially in SLE and polyarteritis.
Red dots occur in nails due to splinter haemorrhages in subacute bacterial endo carditis, rheumatoid arthritis, trauma, and collagen vascular diseases.
Blunt injury produces haemorrhage and causes blue/black discolouration.
Nails become brown in kidney diseases and decreased adrenal activity.
In Wilson's disease, blue colour in a semicircle appears in the nail.
When the blood supply decreases, the nail becomes yellow. Jaundice and psoriasis also cause nails to become yellowish.
In yellow nail syndrome, all nails become yellowish with pleural effusion.
3. Shape of nails:
a. Clubbing: Here, nail base tissues thickens, and the angle between the nail base and the skin obliterates. The nail becomes more convex, and the fingertip becomes bulbous and looks like an end of a drumstick. When the condition becomes worse, the nail looks like a parrot beak.
Causes of clubbing: Congenital Injuries, severe chronic cyanosis, lung diseases like empyema, bronchiectasis, carcinoma of bronchus and pulmonary tuberculosis, abdominal diseases like Crohn’s disease, polyposis of colon, ulcerative colitis, liver cirrhosis and so on. Heart diseases like Fallot’s tetralogy, subacute bacterial endocarditis and so on.
b. Koilonychia: Here, the nails become concave like a spoon. This condition is seen in iron deficiency anaemia. In this condition, the nails become thin, soft and brittle. The average convexity is replaced by concavity.
c. Longitudinal ridging is seen in Raynaud’s disease.
d. Cuticle becomes ragged in dermatomyositis.
e. Nail fold telangiectasia is a sign in dermatomyositis, systemic sclerosis and SLE.
4. Structure and consistency:
a. Fungal infection of nails causes discolouration, deformity, hypertrophy and abnormal brittleness.
b. Thimble nail pitting is characteristic of psoriasis, acute eczema and alopecia Areata.
c. The inflammation of the cuticle or nail fold is called paronychia.
d. Onycholysis is the separation of nail beds seen in psoriasis, infection and after taking tetracyclines.
e. Destruction of the nail is seen in lichen planus and epidermolysis bullosa.
f. Missing nail is seen in nail patella syndrome. It is a hereditary disease.
g. Nails become brittle in Raynaud’s disease and gangrene.
h. Falling of nails is seen in fungal infection, psoriasis and thyroid diseases.
A reduction in blood supply affects the growth of nails. Nail growth is also affected by severe illness. When the disease disappears, the growth starts again, forming transverse ridges. These lines are called Beau's lines and are helpful to date the onset of illness.