Ichthyosis Vulgaris is an inherited or acquired skin condition that occurs when the skin does not shed its dead skin cells. This results in the accumulation of dry dead skin cell patches on the surface of the skin. The origin of the word dates back to its Greek roots, with the name, ‘ichthyosis’ being derived from ‘ichthys’ meaning fish. It is thus known as fish scale disease as the dead skin accumulates in a similar pattern to a fish’s scale. This disease is a type of ichthyosis, a group of related skin conditions that interfere with the skin’s ability to shed dead skin cells and has more than 2o varieties! This particular disease, Ichthyosis Vulgaris is the most common form of inherited ichthyosis.
The Cause?
This disease results from loss-of-function mutations in the gene encoding the protein filaggrin (FLG), which is mapped on the epidermal differentiation complex (a gene complex comprising over 50 genes encoding a protein involved in the differentiation of keratinocytes, the primary cell type of epidermis) on chromosome 1q21. The mutations lead to the defective production of filaggrin. But what is the role of filaggrin?
Filaggrin is a filament-associated epidermal protein required for the binding of keratin fibres in epidermal cells to form an effective and impertenable skin barrier. It helps maintain the pH of the skin, retain moisture in the stratum corneum(the outer layer of the skin) and reduce trans-epidermal water loss (the loss of water that passes from inside a body through the epidermis to the surrounding atmosphere via diffusion and evaporation processes).
The dryness results from the reduced skin hydration associated with defective filaggrin. Excessive scale results from the inability of the skin cells to remain hydrated as they move upward through the stratum corneum.
Clinical features
The symptoms vary in severity and tend to be less severe in a warm, humid climate and more severe in the winter when the air is colder and drier.
Flaky scalp
Itchy skin
Polygon-shaped scales on the skin
Scales that are brown, grey or white
Severely dry skin
Thickened skin
The patches of dry skin typically appear on the elbows and lower legs. It can range from thick dark segments on the shins to deep, painful cracks on the soles of the feet or palms of the hands.
Atopic dermatitis (eczema) is present in 50% of people with ichthyosis Vulgaris. There is also an increased risk of asthma, rhinitis and food allergy.
The diagnosis
This condition is usually just diagnosed from its clinical features but filaggrin mutations can be detected by research laboratories from a buccal smear or saliva sample. A skin biopsy also reveals clues. The histology shows hyperkeratosis (an umbrella term for a number of skin conditions) in the stratum corneum and reduced/absent granular layer. Electron microscopy also shows reduced/absent keratohyalin granules consisting of the protein pro-filaggrin, the precursor to the protein filaggrin.
This disease may be present at birth or appear in the first few years of a child’s life. It can disappear during childhood but can recur in adulthood.
The role of genetics
The condition follows an autosomal dominant pattern. This means that only one parent needs to possess the mutated gene in order to pass it on to his or her child. In rare cases, adults can develop ichthyosis Vulgaris even if they don’t carry the defective gene. It can be associated with taking certain types of medications like cimetidine (an antacid and antihistamine used to treat ulcers and acid reflux), and clofazimine (a drug used to treat leprosy) and nicotinic acid (a B vitamin). Lastly, it can also occur along with other skin disorders and conditions like atopic dermatitis, keratosis pilaris, kidney failure or thyroid disease.
Treatment
There is no cure for this disease, but treatment does exist. Treatment aims to reduce dryness, scaling, and painful fissuring.
This includes,
Exfoliation and moisturisation of skin on a regular, daily basis
Application of emollients (a preparation that softens the skin) with high lipid content
Bath in saltwater
Application of creams or lotions containing salicylic acid, glycolic acid, lactic acid or even urea to exfoliate and moisturise skin.
Oral retinoids such as acitretin or isotretinoin.
Exfoliating with loofah sponges and pumice stones
Living with Ichthyosis Vulgaris.
For people with the inherited type, the outlook is excellent. Many people have a normal lifespan and it can become less serious with age. Only regular treatment of the skin is required. For people with the acquired type, however, treatment of the disease that triggered ichthyosis is vital. If the disease is cured, the ichthyosis goes away.
Written by: Svasti Tewari
Edited by: Sakshi Deshpande
Bibliography
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