When A Patient Has Increased Thickening Of The Skin And Increased Discoloration

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By M. Joel Morse, DPM

The color of lesions or keratodermas depends on the degree of vasodilation, epidermal thickness, the type and density of inflammatory infiltrate, and the amount and location of the melanin.4 The density of melanocytes is similar among all racial and ethnic skin types but they produce more melanin in darkly pigmented people. It is interesting that the dyspigmentation or loss of pigmentation appears to be exaggerated and more noticeable in darkly pigmented individuals.5 In ethnic skin, there is an exaggerated reaction of skin to illness, inflammation and trauma.6
Most of the inherited skin disorders are rare and of minimal medical significance. However, there are others that are life threatening and debilitating. Treatment is available for some conditions but for others, there is no management beyond diagnosis. Identification of a genodermatosis may require referral for a genetics evaluation if this involves a woman of childbearing age.7

Pertinent Insights On Skin Morphology

The PPKs are due to inherited genetic defects, which affect the structural components of the keratinocyte.8 Most keratin disorders exhibit autosomal dominant inheritance.9 In order to resist the mechanical traumas, the plantar region is equipped with highly specialized proteins such as keratins. These form the cytoskeleton of epithelial cells, which are important for structural integrity. In keratoderma, excessive production of altered keratin occurs.10

Patients can inherit these in both an autosomal dominant and recessive fashion. Palmoplantar keratodermas are divided into three subgroups according to their phenotype. Simple keratodermas manifest as lesions only on the palmoplantar skin whereas complex keratodermas are associated with lesions of non-volar skin, hair, teeth, nails or sweat glands. Syndromic keratodermas are associated with abnormalities of other organs such as deafness, cancer, cardiomyopathy and adrenal insufficiency.11

We can divide simple keratodermas into three main groups, the diffuse, focal and punctate PPK. In diffuse PPK, the pattern of keratoderma is uniform across the palmoplantar skin. In focal PPK, the keratoderma develops at pressure points or sites of trauma. Punctate keratoderma has numerous small hyperkeratotic nodules.

Diffuse epidermolytic PPK is the most common pattern of PPK and is also known as Vorner’s disease. It is autosomal dominant and presents within the first months of life. Diffuse non-epidermolytic PPK is also autosomal dominant, is seen early in infancy and is known as Unna-Thost disease.11

With diffuse non-epidermolytic PPK, the lesions on the skin in NEPPK are often susceptible to secondary dermophyte infection and hyperhidrosis is common. Nail changes may occur in both disorders.

Both the hyperkeratosis and erythematous patches can be triggered by trauma to the skin, temperature changes, UV exposure and emotional stress.

Focal palmoplantar keratoderma and punctate palmoplantar keratoderma are less common. Keratosis punctata palmaris et plantaris is an autosomal dominant PPK that develops at 12 to 30 years of age. Physical trauma can induce the lesions and paring and debridement can worsen them.12 The lesions may coalesce into a diffuse pattern on the soles.

Clinically, PPK is characterized by symmetrical keratosis to the palms and soles. In this patient, only the soles were involved. When the keratosis is intense, it may reach the lateral edges of the feet and hands. Some patients may have a red-bluish band that begins at the outer edge of the palms and quickly reaches the center and inner sides of the fingers and toes. Therefore, the plantar skin slowly moves into the dorsal skin “zone” and changes the skin morphology.13 Once the skin morphology changes, it is difficult for it to revert back to the original “dorsal skin.”

Essential Keys To The Differential Diagnosis

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