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Howel-Evans syndrome - Skin
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Howel-Evans syndrome - Skin

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Contributors: Chris G. Adigun MD, Jeffrey D. Bernhard MD, Noah Craft MD, PhD, Lindy P. Fox MD, Lowell A. Goldsmith MD, MPH, Michael D. Tharp MD
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Synopsis

Howel-Evans syndrome, also known as Clarke-Howel-Evans-McConnel syndrome, is a rare genetic disorder characterized by non-epidermolytic palmoplantar keratoderma (NEPPK), oral leukoplakia, and an increased risk of squamous cell carcinoma of the esophagus. This very rare syndrome is inherited in an autosomal dominant fashion. Howel-Evans syndrome has been detected only in patients of Western European descent and in American families of similar ancestry, suggesting this condition is either exceedingly rare or has not yet been reported in other populations. Many studies have mapped the gene defect to a mutation in envoplakin.

Patients present with tylotic changes (a thickening of the skin, or callus formation) of the palms and soles, typically over areas of pressure, in early youth. The hyperkeratotic changes may be confluent over the palms and soles or localized to the areas of pressure, such as the heels and forefeet. Painful fissures are a common complication. In general, the feet tend to be more severely affected, most likely because of increased mechanical pressure in this area. The hyperkeratosis does not extend to the dorsum of the acral areas.

Howel-Evans syndrome is thought to have two separate forms: type A syndrome and type B syndrome. In type A syndrome, the first signs of palmoplantar keratoderma (PPK) arise between ages 5 and 15, whereas in type B syndrome, PPK develops at birth or in the first years of life. In addition, in type B syndrome, PPK lesions are well demarcated and rarely complicated by painful fissuring. It is important to delineate the type of Howel-Evans syndrome presenting in individual patients, as it has prognostic significance: the associated malignancies are more common in type A syndrome.

There have been a number of cases of Howel-Evans with associated ectodermal abnormalities. These findings suggest that this syndrome may be a variant of ectodermal dysplasia and thus support its classification as palmoplantar ectodermal dysplasia type III. Other associations with this syndrome include bronchial carcinoma, esophageal strictures, squamous cell carcinoma of the skin, and gastric and laryngeal carcinoma.

Codes

ICD10CM:
Q82.8 – Other specified congenital malformations of skin

SNOMEDCT:
111030006 – Howel-Evans syndrome

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Diagnostic Pearls

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Differential Diagnosis & Pitfalls

  • Mucosal hyperkeratosis syndrome – autosomal dominant (AD), white lesions of the gingiva, and PPK
  • Focal PPK with oral mucosa hyperkeratosis – focal PPK, oral hyperkeratosis, subungual hyperkeratosis (mutation keratin 16)
  • Pachyonychia congenita type I (Jadassohn-Lewandowsky syndrome) – AD, congenital pachyonychia, hyperhidrosis of the palms and soles, follicular keratosis, palmar and plantar, and leukoplakia of oral and anal mucosa
  • Acrokeratosis neoplastica (Bazex syndrome)
  • Acanthosis nigricans maligna
  • Other keratodermas

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Last Updated: 01/23/2015
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Howel-Evans syndrome - Skin
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Howel-Evans syndrome : Deep skin fissures, Palms and soles, Verrucous scaly plaque, Thickened skin of palms and soles
Clinical image of Howel-Evans syndrome
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