Ichthyosis Hystrix Fact Sheet

Ichthyosis hystrix is a clinical term that has been applied to several disorders that are characterized by very warty, spine like scales. The terms derive from the Greek roots for fish (ichthys) and porcupine (hustriks).

1. Ichthyosis hystrix of Curth-Macklin is a rare from of ichthyosis characterized by palmar plantar hyperkeratosis that is often severe and s6ometimes occurring in a striped or “striated” pattern. Additionally, there are warty or spiny keratotic plaques that may be limited to certain regions like the elbows and knees, or more widely distributed and generalized. The histology of a skin biopsy shows an unusual feature of perinuclear edema with binucleate keratinocytes (epidermal cells containing two nuclei). This disorder is caused by dominant mutations in keratin 1, in the portion of the gene that encodes the ‘tail’ region of the keratin protein. Mutations in other parts of keratin 1 underlie some cases of epidermolytic ichthyosis (see FIRST information on epidermolytic ichthyosis for more information). Many cases are sporadic, representing a new mutation in the affected individual. The disorder is passed on as an autosomal dominant trait, meaning that each offspring has a 50:50 chance of inheriting the disorder from an affected parent (for more information on inheritance, request FIRST’s publication, Ichthyosis: the Genetics of its Inheritance). The severity of the disorder may vary considerably among family members. The treatment for this disorder is similar to that for epidermolytic ichthyosis, and includes topical keratolytic agents and retinoids, both topical and oral.

2. Ichthyosis hystrix of Rheydt is a disorder of generalized warty hyperkeratosis and deafness, also called Hystrix-like ichthyosis deafness, or HID, syndrome. It is caused by mutations in GJB2, the gene encoding for connexin 26. The same mutations also underlie KID (keratitis ichthyosis deafness) syndrome, such that many researchers categorize KID and HID syndromes as a single disorder (for more information see FIRST’s information on KID syndrome.)

3. Ichthyosis hystrix of Lambert (synonym: ichthyosis hystrix gravior, Lambert type) has only been reported in a few families. The clinical phenotype is similar to Ichthyosis hystrix of Curth-Macklin, including the characteristic histopathology of binucleate corneocytes, except that palms and soles are spared in these kindreds. In one kindred, the onset was delayed until childhood, and lesions improved dramatically in the summer. No keratin mutation was identified, suggesting this form to be a genetically distinct entity.

4. Ichthyosis hystrix form of epidermal nevus. Epidermal nevus is the clinical term for disorders in which the hyperkeratosis occurs in linear and swirling patterns within typically larger areas of uninvolved, normal skin. They are mosaic skin disorders caused by several different genes (for more information see FIRST’s information on epidermal nevi). The term ‘mosaic’ indicates that only some of the cells in the body harbor the mutation. In some instances, mosaic disorders are heritable (for more information, request FIRST’s publications, Ichthyosis: the Genetics of its Inheritance and epidermal nevi). The ichthyosis hystrix form of epidermal nevus refers to those with a more warty appearance, and may show features of epidermolytic hyperkeratosis on skin biopsy (for more information, see the FIRST information on epidermolytic ichthyosis). The name can be confusing with other, unrelated types of ichthyosis hystrix, and is therefore not preferred.

5. Other reported types of ichthyosis hystrix. The disorder referred to in older literature as ichthyosis hystrix of Brocq is now considered to be the same as epidermolytic ichthyosis (also referred to as epidermolytic hyperkeratosis; for more information see the FIRST publication on this disorder). Another type, ichthyosis hystrix of Bäyverstedt, has only been reported in a single patient, prior to the advent of genetic diagnosis. The clinical description of this patient is consistent with ichthyosis follicularis alopecia photophobia (IFAP) syndrome, a disorder of cholesterol metabolism.

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1. Richardson EF, Lee JB, Hyde PH et al. A novel mutation and large size polymorphism affecting the V2 domain of keratin 1 in an African-American family with severe diffuse palmoplantar keratoderma of the Ichthyosis Hystrix Curth-Macklin Type. J. Invest. Derm. 2006; 126:79-84.

2. van Geel M1, van Steensel MA, Küster W, et al. HID and KID syndromes are associated with the same connexin 26 mutation. Br J Dermatol. 2002;146:938-42.

3. Biswas P, De A, Sendur S, Nag F, et al. A case of ichthyosis hystrix: unusual manifestation of this rare disease. Indian J Dermatol. 2014;59:82-84.

4. Wang WH, Song SJ, Zhang L et al. Disturbed keratin expression and distinct genotype of ichthyosis hystrix Lambert type. Eur J Dermatol 2010;20:567-572.

This information is provided as a service to patients and parents of patients who have ichthyosis.  It is not intended to supplement appropriate medical care, but instead to complement that care with guidance in practical issues facing patients and parents.  Neither FIRST, its Board of Directors, Medical & Scientific Advisory Board, Board of Medical Editors nor Foundation staff and officials endorse any treatments or products reported here.  All issues pertaining to the care of patients with ichthyosis should be discussed with a dermatologist experienced in the treatment of their skin disorder.

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