Many diseases can affect the nails. The nail is made up of a protein called keratin. The nail grows all the time, the speed of growth decreases with age and poor circulation. Fingernails grow at a rate of about 3mm per month and the toenails grow at a slower rate of 1 mm per month.
To understand the nail disorders and diseases we need to understand the components of the nails first. There are 6 parts mainly the nail bed, nail root, nail plate, cuticle (eponychium), perionychium and hyponychium. Any disruptions of these parts will result in a diseased nail.
Nail Root: It is also known as the germinal matrix that produces most of the volume of nail bed and nail. It is the portion of the nail beneath the skin behind the nail which extends few millimeters into the finger. It does not contain melanocytes (pigment producing cells).
Nail Bed: It is called the sterile matrix which contains nerves, blood vessels and melanocytes. It extends from the nail root to the hyponychium. The nail starts growing from the root and extends down along the nail bed which adds material to make the nail thicker. If nail bed is not smooth the nail may split or have grooves.
Nail Plate: The nail plate is the nail which makes up of translucent keratin. It looks pink because of the blood vessels beneath. The nail plate’s underneath surface has grooves which attaches it to the nail bed.
Cuticle: It is also called eponychium which is between the skin of fingernail and the nail plate which fuses them together providing a waterproof barrier.
Lunula: It is the white half-shaped moon area at the base of the nail.
Perionychium: It is also called the paronychia edge, the part of the skin that overlies the nail plates on its sides. An infection of the skin at this area is called paronychia. It is also the site of ingrown nails.
Hyponychium: This is the junction between the free edge of nail and the skin which is also a waterproof barrier. It is also called the area between the fingertip and nail plate.
Nail Plate Abnormalities
Nail plate abnormalities changes are due to inflammation going on in the nail bed matrix. The abnormalities include:
1.Transverse Ridging of nails: It can be caused by atopic dermatitis,psoriasis, paronychia (infection of the perionychium) and parakeratosis pustulosa. Beau’s lines are horizontal lines across the nails plates of all nails which can be caused by systemic diseases that disrupt nail growth. Diseases like pemphigus, Raynaud’s disease and trauma can cause beau’s lines.
2.Onychorrhexis (longitudinal ridging) of nails: It can be caused bylichen planus, aging, psoriasis, fungal nail infection, picking of nails and Darier.
4.Onychogryphosis: The nail will become thick and curved upwards like a Ram’s horn. It can be due to trauma, aging and psoriasis.
7.Longitudinal splitting of nails: This can be caused by psoriasis,fungal nail infection and lichen planus.
8.Trachyonychia of nails: Nails that look roughened can be caused bylichen planus or tight shoes/heels.
10.Onycholysis (separating of nail plate from nail bed) can be caused byPsoriasis, nail infection, hyperthyroidism, sarcoidosis, trauma, amyloidosis and connective tissue disorders.
There are a number of conditions that causes the nail plate to change color. They will be discussed below:
1.Yellow nails: It can be caused by lung conditions like bronchiectasis and pleural effusions. It can also be caused by sinusitis, cancers, immunodeficiency conditions like HIV, fungal nail infections, psoriasisand rheumatoid arthritis. It is also linked with impaired lymphatic drainage in patients with lymphedema. It can also be caused by nicotine staining from long term smoking.
2.Green Nails: It can be caused by candida or pseudomonas infection of the nails.
3.Brown nails: It can be caused by staining from nicotine, nail varnish, potassium permanganate and Podophylin used for warts treatment. It can also be as a side effect from chemotherapy treatment.
4.White Nails: It can be caused by low albumin levels, chronic kidney failure, Beau’s lines (mentioned above) and manicure procedures. White spotting can be due to fungal nail infection. Terry’s nails characterized by proximal white nail and distal red nail is caused by liver failure, liver cirrhosis, congestive heart failure, diabetes, hyperthyroidism and malnutrition.
Mee’s lines is characterized by partial white lines is caused by arsenic poisoning, Hodgkin’s disease, congestive heart failure, leprosy, malaria, chemotherapy and carbon monoxide poisoning.
5.Red/purplish-black nails: It is caused by trauma with resultant blood clot/bleeding beneath the nail plate.
6.Blue nails: It is caused by drugs like minocycline.
Cuticle and nail fold abnormalities
The cuticle is the area of keratin which joins the posterior nail fold to the nail plate. The abnormalities at this area are:
1.Telangiectasia (dilatation of blood vessels): It can be caused by connective tissue diseases like lupus erythematous and rheumatoid arthritis.
2.Vasculitis changes in the nail resulting in distal nail infarcts (localized dead tissue).
3.Subungal hyperkeratosis: scaling and thickening under the nail plate can be caused by fungal nail infection and psoriasis.
4.Pterygium: scar tissue in the nail matrix can be due to trauma, Steven Johnson syndrome and lichen planus.
6.Paronychia: infection of the perionychium area can be due to bacterial, viral and fungal infections.
Nail shape abnormalities
The nail shape may be abnormal due to various reasons mentioned below:
1.Clubbing of nails: Clubbing is due to the thickening of soft tissue beneath the proximal nail plate resulting in the end of fingers to enlarge and curve downwards. This makes the nail looks like an upside down spoon or drumstick like fingers.
Clubbing of nails is associated with certain cancers (especially those involving lung and pleural) and also lung diseases like bronchiectasis, lung abscess, empyema, pulmonary fibrosis, and cystic fibrosis. Arteriovenous malformations or fistulas, celiac disease, cirrhosis, and inflammatory bowel disease are also associated with clubbing.
Clubbing also occur in patients with heart conditions like congenital heart disease and endocarditis. Sometimes the cause is unknown and not associated with diseases (idiopathic cause).
2.Koilonychia: The longitudinal or transverse concavity of nail resulting in “spoon shaped”. It is often associated with iron deficiency anemia. It can also occur in Raynaud’s disease, SLE, trauma, nail-patella syndrome, acitretin treatment and hemochromatosis.
3.Onychocryptosis: This means in-growing nail with granuloma formations which can be caused by isotretinoin treatment.
4.Pincer shaped nails: This can be caused by psoriasis.
Around the nails, there may be abnormal growths like:
1.Melanocytic nevus: Pigmented skin lesions on nail which are non-cancerous.
2.Viral warts: Viral infection resulting in non-cancerous growth on the skin.
3.Subungal melanoma: A dark pigmented cancerous tumor growth from the nail bed.
4.Keratoacanthoma: A low grade tumor that originates in pilosebaceous glands and resembles squamous cell carcinoma.
5.Squamous cell carcinoma: A cancerous skin condition.
6.Corn: Painful area of thickened skin caused by pressure
7.Inclusion cyst: abnormal membranous sac containing a gaseous, liquid, or semisolid substance.
8.Subungal fibroma: It is a non-cancerous fibrous tumor of connective tissue that occurs under the nail plate.
9. Onychomatricoma: Tumor of the nail matrix
10. Subungual exostosis: Non-cancerous bony growth beneath the nail plate.
11.Myxoid Cyst: abnormal closed epithelium-lined cavity in the body, containing liquid or semisolid material.
12. Pyogenic granuloma: mass of inflamed granulation tissue.