Hyperkeratosis (Thickened Skin)

How hyperkeratosis develops

Skin cells are made in the deeper layer and move up to form a protective layer of dead, keratin-filled cells that normally shed. Hyperkeratosis occurs when:

• the skin makes extra keratin in response to pressure, friction, inflammation or UV damage
• cells do not shed normally (retention), as in some inherited conditions
• a virus, such as HPV in warts, drives excess growth

Types of hyperkeratosis

Causes and risk factors

• tight or ill-fitting shoes, high heels, walking barefoot
• foot deformities such as bunions and hammer toes
• manual work, gym equipment, musical instruments
• chronic sun exposure
• dry skin and cold weather
• smoking, linked with some palmar and plantar thickening
• diabetes and peripheral neuropathy
• genetic conditions
• some medicines and hypothyroidism in acquired keratodermas

Symptoms

• thick, hard, rough or scaly skin
• yellow, gray or brown color
• pain with pressure, especially corns
• cracks or fissures, which can bleed or become infected
• reduced flexibility of the skin

When hyperkeratosis is a concern

• Actinic keratoses can progress to squamous cell skin cancer in a small proportion. They should be treated.
• Calluses in diabetes can hide pressure ulcers underneath. Blood under a callus is a warning sign.
• New, rapidly growing or bleeding rough lesions may be skin cancer and need a biopsy.

Diagnosis

A doctor or dermatologist usually diagnoses the type by examination. Paring a lesion distinguishes a corn (a translucent core) from a wart (tiny black dots of clotted blood vessels). A biopsy is done for uncertain lesions. Genetic testing helps confirm inherited forms.

Treatment

Moisturizers and keratolytics

• urea creams (10% to 40%)
• salicylic acid preparations
• lactic acid or ammonium lactate lotions
• apply after bathing, while skin is damp

Reduce pressure and friction

• shoes with a wide toe box and cushioning
• corn pads, toe separators and insoles
• gloves for manual work
• orthotics for foot deformities

Physical removal

• gentle use of a pumice stone or foot file after soaking
• paring by a podiatrist (not with razors at home, especially if you have diabetes)

Cause-specific treatment

• warts: salicylic acid, freezing (cryotherapy)
• actinic keratoses: cryotherapy, prescription creams (5-fluorouracil, imiquimod), photodynamic therapy
• psoriasis and eczema: steroid creams, vitamin D analogues, systemic treatments
• ichthyosis and keratoderma: keratolytics and, for severe cases, oral retinoids
• seborrheic keratoses: removal only for irritation or cosmetic reasons

Frequently asked questions

What causes hyperkeratosis?

Hyperkeratosis is caused by excess keratin in the skin's outer layer. Common triggers are pressure and friction (calluses and corns), viruses (warts), sun damage (actinic keratoses), inflammation (eczema, psoriasis) and inherited conditions such as ichthyosis.

Is hyperkeratosis dangerous?

Usually not. Most forms, such as calluses and keratosis pilaris, are harmless. Actinic keratoses can be precancerous, and thick calluses in people with diabetes can hide ulcers, so these need medical attention.

How do you treat hyperkeratosis on the feet?

Soak feet, gently file thickened skin with a pumice stone, and apply a urea or salicylic acid cream daily. Wear well-fitting cushioned shoes. People with diabetes should have calluses treated by a podiatrist.

What is follicular hyperkeratosis?

Follicular hyperkeratosis means keratin plugs in hair follicles, causing rough small bumps. The most common form is keratosis pilaris, which affects the upper arms and thighs. Vitamin A deficiency can rarely cause a similar pattern.

Can hyperkeratosis be cured?

It depends on the cause. Calluses and corns go away when pressure is removed. Warts can be cleared. Inherited forms and keratosis pilaris are long term but can be controlled with regular moisturizing and keratolytic creams.