In the ichthyoses-colloquially called fish scale disease-(synonyms: Fish scale; autosomal dominant lamellar ichthyosis; autosomal recessive lamellar ichthyosis; autosomal recessive multiple steroid sulfatase deficiency; bullous congenital ichthyosiform erythroderma (Brocq); Chanarin-Dorfman syndrome; Chondrodysplasia punctata type 2; Comél-Netherton syndrome; Conradi-Hünermann-Happle syndrome; Curth-Macklin; epidermolytic ichthyoses; Happle syndrome; Harlequin ichthyosis; HID syndrome; Hystrix-like ichthyosis with deafness; Ichthyosis; Ichthyosis bullosa; Ichthyosis follicularis with atrichia and photophobia; Ichthyosis hystrix; Ichthyosis linearis circumflexa; Ichthyosis vulgaris; IFAP syndrome; Keratitis-ichthyosis-deafness (deafness) syndrome; KID; Lamellar ichthyoses; non-bullous congenital ichthyosiform erythroderma; peeling skin syndrome; Refsum syndrome; Sjögren-Larsson syndrome; trichothiodystrophy; X-linked associated steroid sulfatase deficiency; X-linked recessive ichthyosis; ICD-10 Q80. -: Ichthyosis congenita; ICD-10-GM L85.0: Acquired ichthyosis) is a group of skin diseases associated with keratoses (cornification disorders) of the epidermis. Hyperkeratosis (accumulation of horny cells/increased callus formation) occurs. The skin surface becomes scale-like, which is why the disease is also called “fish scale disease” (ichthys = fish). Strictly speaking, however, the skin surface is more like reptile skin, since the scales do not overlap as in fish skin, but lie next to each other. A distinction is made between hereditary (inherited) ichthyoses and acquired forms:
- The hereditary ichthyoses are caused by gene mutations (gene changes, gene defects), which lead in different ways to the characteristic appearance of ichthyosis.
- Acquired ichthyoses are ichthyosis-like cornification disorders of the skin that occur during life and are due to another systemic disease, such as tumor diseases, malnutrition, hypovitaminosis, or even the use of certain drugs (see “Etiology – Pathogenesis”/”Causes”).
A further subdivision of ichthyoses is based on whether only the skin or, in addition, other organs are affected:
- Vulgar ichthyoses (occurrence: the disease is not apparent on the day of birth, but develops in the first weeks or months of life).
- Without other features (isolated ichthyosis form).
- With additional features (complex ichthyosis form).
- Congenital ichthyosis (congenital = congenital; occurrence: the disease is already recognizable on the day of birth or shortly thereafter).
- Without other features (isolated ichthyosis form).
- With additional features (complex ichthyosis form).
Mentionable ichthyosis syndromes are:
- Chanarin-Dorfman syndrome
- Comél-Netherton syndrome:
- Autosomal recessive inheritance
- Serine protease inhibitor mutation
- Preferentially affects girls or women (gynecotropy).
- KID syndrome
- Refsum Syndrome
- Sjögren-Larsson syndrome
- Trichothiodystrophy
It is believed that at least 20 types of ichthyosis exist. The four most common forms are:
- Ichthyosis vulgaris
- Autosomal dominant inheritance
- Mildest and most common form (accounts for 95% of all ichthyosis cases)
- In more than 50% of cases, there is an association with atopic dermatitis.
- X-linked recessive ichthyosis vulgaris (XRI).
- Sex-linked inheritance – affects only the male sex.
- Second most common form
- Lamellar ichthyosis (lamellar ichthyosis congenita).
- Autosomal recessive inheritance
- Epidermolytic ichthyosis (Bullous congenital ichthyosiform erythroderma Brocq).
- Autosomal dominant inheritance
The respective forms of ichthyosis are genetically and clinically heterogeneous (inconsistent). Sex ratio:Ichthyosis vulgaris affects males and females equally.X-linked recessive ichthyosis affects only males. In this form, women are conductors, i.e. they are carriers of the hereditary disposition but do not exhibit any characteristic corresponding to it (at most, changes in the cornea of the eye or a slight scaling, especially on the lower legs, can be observed).The prevalence (disease frequency) of ichthyosis vulgaris is 1: 100 to 1: 250.The prevalence of X-linked recessive ichthyosis vulgaris is 1: 4,000 (males). The prevalence of lamellar ichthyosis is 1: 100,000.The prevalence of epidermolytic ichthyosis is 1: 200,000 to 1: 500,000.The prevalence for rarer forms is 1: 300,000.Course and prognosis:The extent of the disease depends on the form of ichthyosis. Hereditary ichthyosis is not curable. Usually only mild symptoms occur. Daily intensive care can alleviate the symptoms.In ichthyosis vulgaris, the prognosis is good. From adulthood on, the symptoms may even regress. Nevertheless, ichthyosis is accompanied by changes in external appearance. The dryness and rigidity (rigidity) of the skin may cause physical disabilities. Some (rare) forms of ichthyosis are even associated with a reduced life expectancy (harlequin ichthyosis).Often, those affected are restricted in their private and professional lives by the external appearance associated with the disease. However, the disease does not only represent a great emotional burden for the affected persons themselves; the parents also face a challenge. For example, caring for the sick child is very time-consuming. Not infrequently, psychosocial care is required for all involved. Acquired ichthyoses are curable if the underlying disease is treated. The most common or important forms of ichthyosis are discussed below.
