Irregular-Appearing Nails (Nail Dystrophy)

How the nail unit works

The nail is made by the matrix, a crescent of living tissue under the cuticle. The pale half-moon (lunula) is the visible part of it. The matrix makes hard keratin that slides forward over the nail bed, which holds it in place. The proximal nail fold and cuticle seal the base against germs.

Where damage occurs determines what you see:

• Matrix damage: pits, ridges, grooves, thinning, splitting, or loss of the nail.
• Nail bed damage: lifting (onycholysis), thickening under the nail (subungual hyperkeratosis), splinter hemorrhages.
• Nail fold damage: loss of the cuticle, wavy ridges across the nail, infection.

For a guide to what individual shape changes mean, see irregular-appearing nails.

Causes of nail dystrophy

Onychomycosis (nail fungus)

Onychomycosis causes about half of all nail dystrophy. Toenails are affected far more often than fingernails. The nail turns yellow, white or brown, thickens and crumbles, and debris builds up under it. Risk rises with age, diabetes, athlete's foot, sweaty feet and communal showers.

Psoriasis

Nail involvement occurs in roughly half of people with skin psoriasis and in most people with psoriatic arthritis. Typical signs are pits, oil-drop discoloration, lifting, crumbling and thickening. It can look identical to fungus, and both can coexist. Read more about nail psoriasis.

Trauma

A single crush injury or repeated microtrauma (running, tight shoes, ill-fitting toe boxes, habitual picking) damages the matrix or bed. Toenails of runners and dancers often thicken and lift. Damaged nails are also more easily infected by fungus.

Lichen planus

Lichen planus can attack the matrix, causing thinning, deep ridges, splitting and, if untreated, permanent scarring where skin grows over the nail bed (pterygium). Early treatment is important to prevent permanent loss.

Other causes

• Eczema and contact dermatitis around the nails: ridging, pitting and cuticle loss
• Chronic paronychia: long-lasting inflammation of the nail fold, often from wet work, leading to wavy ridges
• Alopecia areata: fine pits and rough nails (trachyonychia), especially in children
• Poor circulation and aging: slow-growing, thick, curved toenails (onychogryphosis)
• Medicines: chemotherapy, retinoids and some antibiotics
• Body-wide illness: Beau's lines after serious illness, spoon nails with iron deficiency, clubbing with lung disease
• Inherited conditions: such as pachyonychia congenita and nail-patella syndrome, present from early childhood
• Tumors: warts, myxoid cysts and glomus tumors are usually benign. Melanoma and squamous cell carcinoma are rare but important. Dark streaks are covered under melanonychia.

Diagnosis

1. History: which nails, how long, injuries, footwear, occupation, skin disease, joint pain, medicines and family history.
2. Examination: all fingernails and toenails, skin, scalp, mouth (for lichen planus) and joints. Dermoscopy helps assess pigmented bands.
3. Fungal tests: clippings and debris from under the nail are examined under a microscope, cultured, or tested by PCR. Testing is recommended before oral antifungals, because about half of thick, discolored nails are not fungal.
4. Nail biopsy: for unexplained dystrophy, suspected lichen planus, or a suspicious pigmented band or lump.
5. Blood tests and imaging: when a body-wide cause is suspected, and an X-ray for a lump under the nail.

Treatment

Fungal nails

• Oral terbinafine is the most effective treatment, usually for about 6 weeks for fingernails and 12 weeks for toenails. It requires a prescription and sometimes liver tests.
• Topical lacquers or solutions such as efinaconazole, tavaborole or ciclopirox suit mild disease that spares the base of the nail. They need daily use for up to a year.
• Treat athlete's foot at the same time to prevent reinfection.

Nail psoriasis and lichen planus

• Strong steroid creams or solutions around the nail, sometimes with vitamin D analogs
• Steroid injections into the nail fold for a few affected nails
• Systemic treatment, including biologic medicines, for widespread nail or joint disease

Trauma, aging and habits

• Shoes with a deep, wide toe box and properly trimmed toenails
• Gentle filing to reduce thickness, often by a podiatrist
• Habit reversal for nail picking

Removal

Surgical or chemical removal of a severely thickened, painful nail may be offered, sometimes with destruction of the matrix to prevent regrowth.

Outlook

Even when the cause is cured, the nail improves only as healthy nail grows out: about 6 months for fingernails and 12 to 18 months for big toenails. Fungal infection returns in a significant number of people within a few years. Scarring from lichen planus or severe injury can leave permanent changes.

Frequently asked questions

What is nail dystrophy?

Nail dystrophy is abnormal growth or appearance of a nail, such as thickening, pitting, ridges, splitting, lifting or deformity. It occurs when the area that makes the nail, or the skin beneath or around it, is damaged by infection, injury, skin disease or a body-wide condition.

Is nail dystrophy the same as nail fungus?

No. Fungus is the most common cause, but psoriasis, injury, lichen planus, eczema and aging can produce nails that look the same. That is why fungal testing is recommended before starting antifungal tablets.

Can nail dystrophy be cured?

Often, yes, if the cause is treatable. Fungal infections, injuries and many inflammatory conditions respond to treatment, but the nail takes months to grow out. Nails scarred by severe lichen planus, injury or inherited conditions may stay abnormal permanently.

What does nail dystrophy in one nail mean?

A single dystrophic nail usually reflects a local cause such as injury, a fungal infection, a wart, a cyst or nail fold inflammation. Rarely, it is caused by a tumor. A new dark band, bleeding or a lump in one nail should be examined by a dermatologist.

Does diabetes cause nail dystrophy?

Diabetes raises the risk of fungal nail infection and slow, thick nail growth because of reduced circulation and immunity. People with diabetes should have their feet and nails checked regularly and avoid cutting thick nails themselves if they have numbness or poor circulation.