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

By M. Joel Morse, DPM

Key Questions To Consider

1. What essential question does one still need to ask to help make the diagnosis?
2. What is the tentative diagnosis?
3. Can you list at least three differential diagnoses?
4. What features in this condition differentiate it from other conditions?
5. What is the suitable treatment of this condition?

A 26-year-old African-American female presents with thickening of the skin on the soles and sides of her feet as well as discoloration on two of her toes. She says the discoloration and thickening started eight years ago and has slowly become worse over time.

The examination revealed no thickening on any other part of the body and there was no depigmentation elsewhere on the body. She has no nail or hair involvement. It is not known whether this condition was present when she was an infant or a child. She recalls that it became much worse after a session at the nail salon where the staff rubbed her foot vigorously with a pumice stone. It is more so the thickening rather than the loss of coloration that is difficult for the patient.

The patient notes that her mother has a similar condition but it is not as severe. No other members of the extended family have the condition. The patient notes that she initially was using home remedies that her mother had used and believes these remedies may have made matters worse.

In terms of treatment, the patient has used various products with salicylic acid and urea under the care of a previous doctor with little success. She also notes that mechanical debridement has led to increased thickening of the skin.

Answering The Key Diagnostic Questions

1. Does the patient have depigmentation?
2. Transgressive genetic keratoderma
3. Hyperkeratotic eczema, acquired
punctuate keratoses, arsenical keratoses
4. Hyperkeratosis defines her condition more than leukoderma
5. Systemic retinoids

What You Should Know About Transgressive Genetic Keratoderma

The diagnosis is transgressive genetic keratoderma, which is a form of palmoplantar keratoderma (PPK).1 It consists of hyperkeratosis spreading from the soles (and palms) to the dorsum of the foot across the transgradient line splitting the dorsal skin from the plantar skin. These are rare conditions and are caused by mutations in the keratinocytes.

In this particular patient, there is also noticeable depigmentation in the lower extremity. This condition is known as leukoderma. Most reports show a higher incidence of leukoderma in darker-skinned patients but this may be a result of the ease with which one observes leukoderma on pigmented skin.2 In this patient, it is more so the hyperkeratosis that defines the condition than the leukoderma. The more common causes of leukoderma include: vitiligo, dermatitis (eczema), severe trauma, burns and deep skin infections.

The color of skin and hair comes from the production, transport and distribution of melanin. It is synthesized by melanocytes and transferred to the keratinocytes. Genetic defects can account for many pigmentation defects and can affect the process at many sites along the production of melanin.3

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