Ichthyosis in a Nutshell

Tor Shwayder

doi:10.1542/pir.20-1-5

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Tor Shwayder, MD^*

^*Director, Pediatric Dermatology, Henry Ford Hospital and Children’s Hospital of Michigan; Assistant Professor of Pediatrics and Dermatology, Wayne State University School of Medicine, Detroit, MI.

OBJECTIVES

After completing this article, readers should be able to:

Characterize the presentation of ichthyosis vulgaris.
Describe the presentation of recessive x-linked ichthyosis and the syndrome with which it is associated.
Describe the presentation and etiology of epidermolytic hyperkeratosis.
Identify and describe the two major autosomal recessive primary ichthyoses and their etiologies.
the primary technique for dry skin care.

Overview

The ichthyoses are a heterogeneous group of diseases that share one presentation: scaly skin. Not too long ago, all patients who exhibited this characteristic were lumped into one group. In reality, there are differences ranging from localized to generalized scaling; spiny to flat scales; tiny to huge and plate-like scales; and blistering or redness beneath the scale. Careful observation, histopathology, genetics, and biochemistry allow ichthyoses to be categorized into several classes. The term “ichthyosis” comes from the Greek, meaning fish. To understand the ichthyoses, one must be familiar with the internal to external progression of normal skin.

Normal Skin

Ichthyoses represent abnormalities in the formation and desquamation of the keratinocytes, the most common epidermal cell. The epidermis is arranged in four layers: basal cell, squamous cell (or spiny), granular, and horny. As keratinocytes progress from the basal layer to the horny layer, different keratin proteins are manufactured. Keratins form a structural framework inside the cell that holds the shape similarly to steel girders inside a blimp. As skin tissue matures and moves outward, the keratin proteins are manufactured in a predictable sequence, but mutations can lead to keratins that have different size, shape, and assembly defects, which can affect the size and shape of the cell. At the basal layer, keratin types 5 and 14 are expressed, and as the cell moves up, keratins 1 and 10 are expressed in the spinous and granular layers. Depending on where the genetic error in keratin coding …