6.1.5 Palmoplantar Keratoderma

Keratosis palmoplantaris.

Includes genetic as well as acquired forms. Uncommon disorders. Autosomal dominant (1:100 000) and autosomal recessive disorders.

Persistent thickening of the epidermis of palms and soles.

Hereditary palmo-plantar keratodermas (PPK) include a high number of genodermatoses with different prognoses with multiple associated cutaneous and extracutaneous features.

Many different genes have been identified in diffuse PPK secondary to keratin mutations (epidermolytic and non-epidermolytic) in an autosomal dominant and recessive pattern of inheritance. Many different clinical variants with multiple implicated genes in focal, striated complex and syndromic hereditary PPKs.

In acquired PPKs, a spectrum of disorders of different etiology may be involved: occupational, irritative, contact allergies, keratoderma climatericum, chemicals, drugs, systemic diseases, malignancies, infectious disorders, inflammatory dermatoses, lymphomas, paraneoplastic etc. 

Onset usually in infancy, symmetrical, palms and soles thickened, yellow and fissured with diffuse or focal symmetrical lesions, often hyperhidrosis. Some variants may worsen by age. Association with other ectodermal defects possible.

Acquired PPK may also be focal, diffuse or punctate.

Palms and soles. In some cases may extend to the dorsal surfaces of the hands and feet, wrists and Achille’s tendons.  Different disorders may present associated hyperkeratotic cutaneous or mucosal lesions, often involving the extensor surfaces of the extremities (knees, elbows), hair, nail and teeth abnormalities.

1. Depending on aetiology: Hereditary or acquired PPK

          1.1 Hereditary PPK

Diffuse or focal hyperkeratosis, with or without associated findings, exact classification based on molecular genetic identification of mutations. Hereditary PPK can be divided into:

-    Non-syndromic isolated PPK: Predominant or unique palmo-plantar involvement

-    Complex PPK:  Non-syndromic PPK with additional distinctive cutaneous and adnexal manifestations

-    Syndromic PPK: PPK associated with specific extracutaneous manifestations

• PPK associated with sensorineural deafness
• PPK associated with prominent mucosal involvement
• PPK associated with cardiomyopathy and woolly hair
• PPK associated with other systemic signs

          1.2. Acquired PPK

  2. Classification according the observed clinical patterns: 

-    Diffuse PPK: Generalized epidermal thickening involving the entire palmo-plantar surfaces.

-    Focal PPK: Multiple callosities (soles)

-    Striate PPK: Linear hyperkeratotic bands in correspondence with the underlying tendons

-    Punctate PPK: Multiple papular lesions with epidermal thickening (with a central pit or spiny projection) 

No abnormalities are usually detected. For certain forms in 1.1. molecular profiling has to be done, and for 1.2 individual workup necessary depending on the underlying disease.

Non-epidermolytic PPK: Acanthosis, hypergranulosis, hyperkeratosis, orthokeratosis.

Epidermolytic PPK variants: Perinuclear vacuolization, granular degeneration of keratinocytes, large, irregular keratohyaline granules. Subcorneal intaepidermal cleavage.

In acquired PPK the histopathological features are non-specific: hyperkeratosis with orthokeratosis or parakeratosis and different amount of inflammation. 

Chronic.

Secondary fungal infection. In syndromic PPK the associated features (cardiomyopathy) may have prognostic implications.  Psychosocial problems.

Clinical history and features combined with histopathological findings. Positive family history and onset in infancy or childhood may be helpful to distinguish between hereditary and acquired PPK. The clinical pattern (diffuse, striate/focal or punctate) along the presence with other cutaneous or extracutaneous manifestations may also be helpful. In some cases,  the genetic study may confirm the diagnosis. In acquired PPK a systematic search for an underlying cause is mandatory.

The different acquired etiologies that may lead to PPK. Other causes of palmoplantar keratoses: Hand dermatitis (hyperkeratotic, fissured), Psoriasis and hyperkeratotic lesions in secondary syphilis, cutaneous T-cell lymphoma (especially Sézary syndrome), dyskeratosis folicularis (Darier).

Topical keratolytics: salicylic acid (5-10%), urea, lactic acid, vitamin A acid, abrasive soaps, mechanical removal. Customized footwear.

Systemic: low dose retinoids (acitretin) or 9-cis retinoic acid.

In the acquired variants of PPK: To identify (if possible) and treat the underlying etiology.