Palmoplantar keratoderma

Palmoplantar keratoderma is a term used to define a marked thickening of the skin on the palms and soles, either as a focal entity, or diffuse. Keratoderma can be inherited, acquired, and rarely, paraneoplastic ie secondary to an internal malignancy.

This chapter provides a practical overview of keratoderma, and is set out as below:

• Keratoderma is usually acquired, but can be inherited as an autosomal dominant or autosomal recessive pattern 
• The feet are generally more severely affected than the hands. Occasionally keratoderma can affect other parts of the body
• It can be difficult to differentiate between the different types of keratoderma, however, the management principles are similar, and as such the key diagnostic elements are to exclude the rare malignant or other systemic causes

Clinical classification

Keratoderma can be defined by its clinical appearance, although there is often overlap:

• Diffuse - the whole of the palmar or plantar skin
• Focal - the pressure points are more severely affected eg heel margins and either side of the metatarsal arch 
• Punctate keratoderma - multiple small scattered lesions
• Striate - longitudinal involvement, especially along the fingers

Logical approach to management

For the purposes of this website keratoderma has been grouped as follows:

• Hereditary - with symptoms presenting in early childhood
• Acquired when it presents in later life
• Rarely keratoderma can be associated with malignancy

Hereditary keratoderma

Diffuse keratoderma 

• Several, rare, inherited forms have been described, most being autosomal dominant, although some are autosomal recessive 

• Epidermolytic keratoderma (Vorner's keratoderma) and non-epidermolytic keratoderma (Thost-Unna keratoderma) are two of the best described forms:
  • Both are autosomal dominant
  • Clinically the features can be indistinguishable with the development, usually in infancy, of diffuse, yellow, thickened skin affecting the palms and soles. There is usually a well-defined erythematous border
  • The two conditions vary in their histological features

• Several others types have been described. One particularly notable, but very rare condition, is keratoderma with scleroatrophy - in addition to diffuse keratoderma (especially of the palms) there is tightening and atrophy of the fingers and nails (sclerodactyly), and an increased risk of cutaneous squamous cell carcinoma

Focal and striate keratoderma

• ​​Focal keratoderma
• ​Characterised by the development of localised areas of painful skin thickening, and sometimes blisters, over the pressure points eg the heel margins and either side of the metatarsal arch of the feet. The palms of the hands are less severely affected. Some people with focal palmoplantar keratoderma also have abnormalities of the fingernails and toenails

• There are several inherited types, which are all rare. One of the more commonly reported conditions is pachyonychia congenita, which is characterised by focal keratoderma and subungual hyperkeratosis of the distal nails ususally usually becoming apparent within the first few years of life. Rarely, pachyonychia congenita can arise in older children and adults when it is known as pachyonychia congenita tarda

• Striate keratoderma 
  • ​Is usually inherited as autosomal dominant
  • It is characterised by linear hyperkeratosis running along a finger and onto the palm. The soles can also be affected
  • Patients may also have areas of focal keratoderma
  • Some inherited cases of focal and striate keratoderma can occasionally have extracutaneous features, such as hearing impairment, sparse hair, woolly hair with cardiac disease, and focal hyperkeratosis with oesophageal carcinoma (referred to as the Howell-Evans' syndrome or 'tylosis with oesophageal carcinoma') 

Punctate keratoderma

• ​Is characterised by multiple, small, maculo-papular lesions on the palms and soles
• Most cases are autosomal dominant 
• It presents most commonly in young adults
• Distribution - mainly the palms and soles, although a few cases predominantly affect the medial and lateral margins of the hands and feet 
• Morphology - lesions may be atrophic, firm and scaly, have spiny projections, or occasionally warty

Acquired keratoderma

Is more common than inherited keratoderma. Can be focal or diffuse. There are many causes including:

• Moderate-severe callosities
• Inflammatory - eczema, psoriasis and lichen planus
• Infective - crusted scabies, syphilis, Reiter's disease 
• Drugs - verapamil, lithium, arsenic and fluorouracil
• Systemic disease - thyroid disease, diabetes mellitus, and malignancy (refer below) 
• Chronic lymphoedema
• Keratoderma climactericum - characterised by hyperkeratosis of the palms and soles in women of menopausal age, and associated with obesity and hypertension. It usually affects the sole of the feet around the margins of the heel and under the metatarsal heads. The palms of the hands may be affected with discrete, centrally placed lesions. Patients present with erythema, hyperkeratosis and painful fissures 

Keratoderma associated with internal malignancy 

The Howell-Evans' syndrome is inherited and should be suspected from a family history of oesophageal carcinoma.

Paraneoplastic associations: 

• Acquired diffuse palmoplantar keratoderma has occasionally been associated with carcinoma of the bronchus

• Keratoderma with features of acanthosis nigricans, especially if atypical with a rapid progression of florid skin lesions and additional mucosal membrane involvement. The vast majority are associated with adenocarcinoma of the stomach, but other malignancies sometimes found include other GI tract tumours, lung, uterus, ovaries, and urinary tract

• Tripe palms - the appearance differs to that of keratoderma with thickened velvety palms that have the appearance of tripe. It is often associated with acanthosis nigricans (AN). Approximately 90% of cases of tripe palms are associated with internal malignancy. The cutaneous features usually pre-date the diagnosis of the cancer. When seen in conjunction with AN the underlying malignancy is most commonly stomach (35%) or lung (11%). In cases where tripe palms occur without AN, lung cancers are usually responsible. Less commonly associated malignancies include head and neck tumours, and tumours of the genitourinary tract

• Basex's acrokeratosis paraneoplastica - has features similar to psoriasis. It is associated with squamous cell carcinoma of the upper aerodigestive tract (oral cavity, pharynx, larynx, oesophagus). Three stages have been described:
• Stage 1: characterised by poorly defined psoriasiform plaques involving the ears (helices), nose, fingers, and toes. A painful paronychia develops with no evidence of bacterial or fungal infection. Nail changes include dystrophy, horizontal and vertical ridging (75%), subungual hyperkeratosis, and nail plate atrophy 
• Stage 2: characterised by involvement of larger and more proximal cutaneous regions; a palmoplantar keratoderma with central clearing; and there may be involvement of the cheeks
• Stage 3: characterised by involvement of the legs, knees, thighs, and arms

• Most patients will not require investigation

• In cases of acquired palmoplantar keratoderma, in the absence of an underlying inflammatory dermatosis or other obviously benign condition (eg multiple callosities, keratoderma climactericum), consider:
  • Skin scrapings to send for mycology to exclude tinea
  • TFT and fasting glucose levels in symptomatic patients
  • Rarely, more detailed investigations if an underlying malignancy is suspected (refer to the section above in clinical findings) 

• Urea-based emollients are the most effective and can be used under occlusion at night (eg cotton gloves for the hands and socks for the feet - see below) 

• Very thick scale on the feet can be treated by higher strengths of urea (eg Flexitol 25% ® Urea Heel Balm; various 20% urea products can be purchased online) should be applied to the skin under a damp sock with a dry sock on top, starting 3 nights a week. In Secondary Care 10-20% preparations of salicylic acid in yellow soft paraffin can be used, however, these are often made up as a 'special' and can be costly

• Diprosalic ointment ® can be used at night (under occlusion if needed) if there is associated inflammation eg secondary to eczema or psoriasis

• Physical methods of scale removal such as Pumice stones, emery boards, and paring (with or without soaking in water). Some patients may benefit from referral to podiatry if they are not capable of removing scale themselves and/or if advice is need to help relieve pressure from foot involvement

• Systemic retinoids, especially acitretin, can be provided by specialists. They can be very effective for some patients, but cannot be used in fertile women due to their teratogenicity