The signs and symptoms of IT can be classified according to the type they belong to:

• Ichthyosis vulgaris: In this case the skin might appear normal at birth, but begins to dry developing fine white scale by the age of 5 years. The most affected regions of the body are abdomen, arms and legs. Another typical sign is keratosis pilaris, a very common form of dry skin characterized by the appearance of rough and red bumps on the skin [15], which is frequently associated with excessively lined palms. Atopic eczema is another classical signs, appearing in 50% of the cases.
• Recessive X-linked ichthyosis: In this type the disorder appears very early in life, within 6 months from birth, with the development all over the skin of fined or rhomboid grey/brown scales. Scaling is most prominent on the extremities as well as neck, trunk and buttocks, while on the contrary to what happens in ichthyosis vulgaris palms appear normal. Other classical signs include corneal opacities and undescended testicles, appearing respectively in 50% and in 5-20% of the cases. The disorder occurs only in males.
• Autosomal recessive congenital ichthyosis-1 (ARCI1): Also appearing very early in life, this type causes the appearance of a collodion membrane, which afterwards cracks. One of the most life-threatening forms is the already mentioned harlequin ichthyosis, where the collodion membrane is very severe and appears together with ectropion (drooping lower eyelids), eclabium (out-turned lips) and contractures. The typical variants include lamellar ichthyosis, characterized by a dark scaling all over the body especially on arms and legs, nonbullous congenital ichthyosiform erythroderma (NCIE), with the scaling appearing as white, superficial and semi-adherent that is frequently accompanied by erythroderma, and palmoplantar keratoderma, which varies based on the gene involved.

• Keratinopathic ichthyoses: The skin appears moist, red, and tender, full of filled blisters which might afterwards become infected and give rise to a foul smell. Scaling is thick, white to brown in color, and appears especially over extensor joints. Growth failure is very frequent among affected individuals, together with the appearance of a general mosaic appearance of the skin. The major variants include epidermolytic ichthyosis, ichthyosis hystrix of Curth-Macklin (IHCM), and the already mentioned palmoplantar keratoderma.
• Acquired ichthyosis: This form is very similar to ichthyosis vulgaris, even though it develops later in life. As previously stated, this form might be the clinical manifestation of an underlying disease such as Hodgkin lymphoma, or the severe side effect of a particular drug.

• Hodgkin Lymphoma

  Associated diseases Malignancy non-Hodgkin lymphoma Kaposi sarcoma multiple myeloma leiomyosarcoma breast ovarian cervical Non-malignancy autoimmune systemic inflammatory disease endocrine/metabolic disorders HIV infection medication-related Generalized [radiopaedia.org]

  Other cancers that have been related with AI include non-Hodgkin lymphoma, Kaposi's sarcoma, multiple myeloma, leiomyosarcoma and breast, ovarian, cervical and lung cancer. [archbronconeumol.org]

  Acquired cases are most often caused by an underlying disorder such as: Cancer: Hodgkin's disease, non-Hodgkin lymphoma (including mycosis fungoides), lung cancer, breast cancer, ovarian cancer, and cervical cancer Sarcoidosis Leprosy Thyroid disease [verywellhealth.com]

  Other cancers associated with the condition include: non-Hodgkin’s lymphoma; cutaneous T cell lymphoma; lymphomatoid papulosis; multiple myeloma; breast, lung, cervical and liver cancers; and sarcomas. [dermcoll.edu.au]

  lymphoma is the most common Hypothyroidism Renal failure Bowel conditions causing malabsorption HIV infection Leprosy Drugs - several medications have been associated including allopurinol, hydroxyurea, nicotinic acid, cimetidine and clofazimine Images [pcds.org.uk]

• Sepsis

  In the newborn period, the risk for infection (sepsis) is great, therefore it is important that appropriate therapies be initiated immediately following delivery. [myriadwomenshealth.com]

  During the neonatal period, there is a risk of sepsis and hydro-electrolytic troubles. The disease often remains stable over the life, with periods of exacerbation. The life expectancy is normal. [orpha.net]

  Infection HI neonates are particularly prone to sepsis. [pediatrics.aappublications.org]

  […] respiratory infections Frequent respiratory infections Multiple respiratory infections respiratory infections, recurrent Susceptibility to respiratory infections [ more ] 0002205 Renal insufficiency Renal failure Renal failure in adulthood [ more ] 0000083 Sepsis [rarediseases.info.nih.gov]

  Fissuring and denudation can provide a means of entry for microorganisms, leading to skin infections and sepsis. [ncbi.nlm.nih.gov]

• Recurrent Infection

  EI can impact the quality of life and may cause social handicap due to the skin's aspect, pain, pruritus, body odor, and/or recurrent infections. EI can also be life-threatening during the neonatal period due to infections and/or dehydratation. [orpha.net]

  If recurrent infections are a problem, adding bleach to your child's baths (along with the bath oil or wash) can help to reduce the bacteria on the skin and prevent further infections. See our fact sheet Skin infections – bleach baths. [rch.org.au]

  Cardiac and hematologic abnormalities, hypogonadism and recurrent infections can also occur.5-9 Hairs are short, brittle and coarse. [scielo.br]

  Some people with mal de Meleda have recurrent fungal infections in the thickened skin, which can lead to a strong odor. [ncbi.nlm.nih.gov]

• Pathologist

  Some of the diagnostic steps for Ichthyosis Vulgaris may include: A through family history and a complete physical examination Complete blood count (CBC) Examination of peripheral blood smear under a microscope by a pathologist Genetic testing for specific [dovemed.com]

  All this information is collegially discussed by the dermatologist, geneticist and pathologist. [ojrd.biomedcentral.com]

• Corneal Opacity

  There may be associated corneal opacities that do not affect vision. Sjögren-Larsson syndrome is an autosomal recessive ichthyosis associated with progressive spastic paralysis and mental retardation. [ncbi.nlm.nih.gov]

  Approximately 25% of female carriers have minor corneal opacities. The corneal opacities are not known to affect visual acuity. An example of findings in X-linked ichthyosis is shown in the image below. [emedicine.medscape.com]

  Extracutaneous manifestations like testicular maldescent and/or corneal opacities are possible for rare cases, if the ichthyosis is part of a disease syndrome (syndromic RXLI; see this term). [orpha.net]

  Other classical signs include corneal opacities and undescended testicles, appearing respectively in 50% and in 5-20% of the cases. The disorder occurs only in males. [symptoma.com]

• Decrease in Height

  […] body height Small stature [ more ] 0004322 Showing of 22 | Last updated: 3/1/2020 Making a diagnosis for a genetic or rare disease can often be challenging. [rarediseases.info.nih.gov]

• Dry Skin

  Marie Lodén, The Use of Urea in the Treatment of Dry Skin, Treatment of Dry Skin Syndrome, 10.1007/978-3-642-27606-4_33, (481-492), (2012). [doi.org]

  Other treatments include keeping the skin moist with moisturizers and avoiding having the skin dry out. [msdmanuals.com]

  E45 Cream is an effective emollient that is specially formulated by our dry skin experts and can be used to help manage dry skin associated with ichthyosis. [e45.co.uk]

  Ichthyosis (IT) is a term referring to at least 28 different genetic skin disorders, where the skin predominantly appears dry, thickened, scaly and cracked. [symptoma.com]

• Skin Thickening

  The project in short Sjögren-Larsson Syndrome (SLS) is a rare inborn error of aldehyde metabolism characterized by severe skin thickening (ichthyosis), retinal disease, and neurological dysfunction. [lipotype.com]

  Symptoms Symptoms may include any of the following: Dry skin, severe Scaly skin (scales) Possible skin thickening Mild itching of the skin The dry, scaly skin is usually most severe on the legs. [mountsinai.org]

  Symptoms Dry skin, severe Scaly skin ( scales) Possible skin thickening Mild itching of the skin The dry, scaly skin is usually most severe on the legs. But it can also involve the arms, hands, and middle of the body. [nicklauschildrens.org]

  Symptoms may include any of the following: Dry skin, severe Scaly skin (scales) Possible skin thickening Mild itching of the skin The dry, scaly skin is usually most severe on the legs. [medlineplus.gov]

  Symptoms Symptoms may include any of the following: Dry skin, severe Scaly skin ( scales ) Possible skin thickening Mild itching of the skin The dry, scaly skin is usually most severe on the legs. [ufhealth.org]

• Anhidrosis

  Pruri¬tus, skin fragility, ectropion and anhidrosis are sometimes associated with the rare types of ichthyosis. [medicaljournals.se]

  Severe anhidrosis is common in childhood, but often improves with adolescence. Growth can be delayed. [pcds.org.uk]

  Systemic Features: All patients have anhidrosis resulting in alacrima and xerostomia with heat intolerance. Nails and hair are normal. [disorders.eyes.arizona.edu]

  Anhidrosis: Problems with sweating are often overlooked for patients with ichthyosis. When the outside temperature is above 70°F, patients should be careful, avoiding strenuous activity and increasing fluid intake. [jaad.org]

• Eruptions

  We report a 21-year-old man with recurrent bullous eruptions and severe itching on the lower legs and feet since 5 years of age. Dry, dirty brown, tile-like scales covered his lower legs with dystrophic toenails. [ncbi.nlm.nih.gov]

  Similarly in our case, we reported multiple carious teeth, over retained deciduous teeth, delayed eruption of permanent teeth and lingually erupting premolar tooth. [omicsonline.org]

  Patient's parent gave a history of delayed eruption of his milk teeth. The boy was born to a consanguineous couple as a collodion baby. [ijpd.in]

  Types: xeroderma, xerodermia a mild form of ichthyosis characterized by abnormal dryness and roughness of the skin xeroderma pigmentosum a rare genetic condition characterized by an eruption of exposed skin occurring in childhood and photosensitivity [vocabulary.com]

  Allergic contact dermatitis Asteatotic eczema Drug eruptions Harlequin ichthyosis Impetigo Irritant contact dermatitis Lamellar ichthyosis Pediatric atopic dermatitis X-linked ichthyosis. [lecturio.com]

• Exfoliation of the Skin

  The main goal of treatment is to moisturize and exfoliate. This helps prevent dryness, scaling, cracking and build-up of skin. People with ichthyosis need to bathe, moisturize and exfoliate their skin on a daily regular basis. [aocd.org]

  The main goal of treatment is to moisturise and exfoliate. This helps prevent dryness, scaling, cracking and build-up of skin. People with ichthyosis need to bathe, moisturise and exfoliate their skin on a daily regular basis. [novatretin.co.nz]

• Kidney Failure

  It may be associated with an internal disease (for example, kidney failure, cancer, AIDS). You should consult a doctor regarding the diagnosis. [web.archive.org]

  failure HIV infection Autoimmune disorders: systemic lupus erythematosus, dermatomyositis Acquired ichthyosis has also been associated with the use of certain medications, such as niacinamide, Tagamet (cimetidine) and Lamprene (clofazimine). [verywellhealth.com]

  In adults, the disease is called acquired ichthyosis vulgaris, and can be caused by other diseases, including kidney failure, certain cancers, sarcoidosis, leprosy, and human immunodeficiency virus (HIV). [my.clevelandclinic.org]

  Other conditions such as chronic liver disease, kidney failure, thyroid and parathyroid diseases, sarcoidosis, leprosy, bone marrow related conditions and rarely autoimmune connective tissue diseases (e.g. lupus, dermatomyositis) may also cause ichthyosis [dermcoll.edu.au]

  Diseases that can trigger ichthyosis include kidney failure, some cancers, and human immunodeficiency virus (HIV). Whether ichthyosis vulgaris begins in childhood or adulthood, it can be so mild that it is mistaken for extremely dry skin. [wederm.com]

The diagnosis of IT is mainly based on the physical examination of the skin. As it is an inherited disorder, a family history of the patient might be useful to detect and classify the disorder. Both approaches can be largely supported by performing a skin biopsy and genetic testing. The presence of systemic disorders such as diabetes mellitus can support the diagnosis of IT [16].

As IT is mainly an inherited disorder, no permanent cure has been developed, and treatment is largely based on palliative approaches. Very common is the application of creams and emollient oils to hydrate the skin, especially those products containing lactic acid which have proved to be exceptionally effective to treat dry skin. Other classes of chemical compounds which appear effective in treating IT include propylene glycol and retinoids. Exposure to sunlight might improve the condition in certain cases, even thought it can have severe side effects, while the use of oral antibiotics to avoid secondary infections is highly recommended.

Other effective measures can include the use of non-soap cleansers, bathing in salt water, rubbing with a pumice stone to remove scales, or the use of vitamin D supplementations, especially in the most severe cases.

As the severity of IT depends on the type taken into consideration, prognosis too varies according to the case. For the majority of the patients who suffer for mild forms of IT, topical therapy is already sufficient and generally they do well after treatment. On the contrary, prognosis is not good in the most severe forms involving major systemic disorders, where the skin is only the minor clinical concern for the patients.

For example, prognosis is very good with ichthyosis vulgaris, where the major concern is skin moisturization, but not with X-linked ichthyosis, where patients are at higher risk to develop testicular cancer, a far more lethal disorder than IT itself.

The formation of epidermis is the result of an intricate interaction among several components, such as intracellular and extracellular proteins, lipids, nuclear filaments, and key enzymes, each one of them playing a pivotal role in skin development. Any defects in one of this component might be catastrophic and can lead to the occurrence of IT. Although generally inherited, some forms of IT can be acquired. These are usually caused by certain medications, including some of frequent use such as clofazimine, lipid-lowering agents, and butyrophenone [3] [4] [5]. It should be noted that several important systemic disorders, such as lymphoma [6] [7] or diabetes mellitus [8], might also cause IT.

The major genes and proteins involved in IT include:

• Filaggrin: A filament-associated protein which plays an important role in epidermal homeostasis by binding to keratin fibers in epithelial cells.
• Keratins: A group of fibrous structural proteins representing one of the major components of cytoskeleton. 
• ATP-binding cassette transporter 12: Transmembrane proteins using the energy coming from ATP molecules to perform key biological processes such as substrates translocation, RNA translation and DNA repair [9] [10].
• Steroid sulfatase: Sulfatase enyme with a pivotal role in steroids metabolism, found in great abundance as monomer in the endoplasmic reticulum. 
• Ceramide synthases: Integral membrane proteins involved in the synthesis of ceramide (an important membrane component) in the endoplasmic reticulum [11].

The incidence and prevalence of IT vary according to the type considered as well as the population under investigation. For instance, prevalence of ichthyosis vulgaris has been estimated to be around 1 case every 250 individuals in UK [12] and around 2 cases every 100 individual in China [13]. The prevalence of the other less frequent forms is lower, on average around 1 case every 300,000 individuals [14].

As previously said, the underlying cause of the IT clinical manifestations is the genetic mutations on the genes playing a pivotal role in skin development, which result in a marked increase of keratinization. The major clinical manifestation is undoubtedly the presence of scales all over the skin of the affected person, whose size and thickness vary according to the particular type of IT considered. The degree of scaling is an important pathological factor in itself, as it might cause or extensively influence other important clinical manifestations such as erythema, pruritus, bacterial colonization, and hair loss. Furthermore, as these mutated genes and proteins might play an important role for the entire body, they can frequently cause systemic clinical manifestations.

IT is a chronic condition which requires a lifelong treatment. Therefore, any of the previously indicated measures should be performed permanently during the entire course of the patient’s life, especially to avoid major side effects such as chronic water loss or dangerous skin infection, which might severely affect the quality of life in adults and impair growth and development in children.

The name ichthyosis (IT) derives from the Greek word ἰχθύς (ichthys) meaning fish, with clear reference to the fishy resemblance of the skin of the people affected. The severity of this disorder varies very much, according to the type taken into consideration. The most common type of IT is undoubtedly ichthyosis vulgaris accounting for the 95% of the cases [1] , which is mild in nature and frequently mistaken for normal dry skin. By contrast, one of the most life-threatening forms is harlequin type ichthyosis, which causes the skin to thicken and frequently results in fatal infections.

These skin disorders are the result of the presence of excessive amounts of dry surface scales due to marked keratinization or cornification, as a consequence of abnormal epidermal differentiation and metabolism. To date, five major types of IT have been officially described, which include ichthyosis vulgaris, lamellar ichthyosis, epidermolytic hyperkeratosis, congenital ichthyosiform erythroderma, and X-linked ichthyosis. These can be differentiated based on the general clinical manifestations, histological findings, as well as genetic makeup [2].

Ichthyosis (IT) is a term referring to at least 28 different genetic skin disorders, where the skin predominantly appears dry, thickened, scaly and cracked. The name of this group of disorders comes from the Greek word ἰχθύς (ichthys) meaning fish, with clear reference to the fishy resemblance of the skin. This disorder originates from one or more defects in skin development, which might have catastrophic consequences in terms of abnormal clinical manifestations.

There are 5 major types of IT: Ichthyosis vulgaris (the most common of the five), recessive X-linked ichthyosis, autosomal recessive congenital ichthyosis-1 (ARCI1), keratinopathic ichthyoses, and acquired ichthyosis. Each one of these has its own particular repertoire of clinical manifestations, the most common of which include dry skin, rough and red bumps on the skin, atopic eczema, scales, corneal opacities and collodion membrane.

As IT is mainly an inherited disorder, no permanent cure has been developed, and treatment is largely based on palliative approaches. Very common is the application of creams and emollient oils to hydrate the skin, especially those products containing lactic acid which have proved to be exceptionally effective to treat dry skin. Other effective measures can include the use of non-soap cleansers, bathing in salt water, rubbing with a pumice stone to remove scales, or the use of vitamin D supplementations, especially in the most severe cases. IT is a chronic condition which requires a lifelong treatment. Therefore, any of the previously indicated measures should be performed permanently during the entire course of life, especially to avoid major side effects such as chronic water loss or dangerous skin infection.

1. Okulicz JF, Schwartz RA. Hereditary and acquired ichthyosis vulgaris. International Journal of Dermatology 2003 42 (2): 95–8. 
2.  Moeschler JB, Shevell M. Clinical genetic evaluation of the child with mental retardation or developmental delays. Pediatrics. Jun 2006;117(6):2304-16. 
3. Caver CV. Clofazimine-induced ichthyosis and its treatment. Cutis. 1982;29:341-343. 
4. Williams ML, Feingold KR, Grubauer G, et al. Ichthyosis induced by cholesterol-lowering drugs: implications for epidermal cholesterol homeostasis. Arch Dermatol. 1987;123:1535-1538. 
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12. Wells RS, Kerr CB. Clinical features of autosomal dominant and sex-inked ichthyosis in an English population. Br Med J. 1966;1:947-950. 
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