A physician often can diagnose ichthyosis by looking at the skin. A family history is very useful. In some cases, a skin biopsy is done to help to confirm the diagnosis. In some instances, genetic testing may be helpful in making a diagnosis. Diabetes has not been definitively linked to acquired ichthyosis or ichthyosis vulgaris; however, there are case reports associating new onset ichthyosis with diabetes.

Ichthyosis has been found to be more common in Native American, Asian, Mongolian groups. There is no way to prevent ichthyosis.

Ichthyosis is a genetically and phenotypically heterogeneous disease that can be isolated and restricted to the skin manifestations or associated with extracutaneous symptoms. One of which is limb reduction defect known as CHILD syndrome; a rare inborn error of metabolism of cholesterol biosynthesis that is usually restricted to one side of the body. A research done in Egypt proved that it is not a child syndrome and discussed all the case report.

The diagnosis of harlequin-type ichthyosis relies on both physical examination and certain laboratory tests.

Physical assessment at birth is vital for the initial diagnosis of harlequin ichthyosis. Physical examination reveals characteristic symptoms of the condition especially the abnormalities in the skin surface of newborns. Abnormal findings in physical assessments usually result in employing other diagnostic tests to ascertain the diagnosis.

Genetic testing is the most specific diagnostic test for harlequin ichthyosis. This test reveals a loss of function mutation on the ABCA12 gene. This gene is important in the regulation of protein synthesis for the development of the skin layer. Mutations in the gene may cause impaired transport of lipids in the skin layer and may also lead to shrunken versions of the proteins responsible for skin development. Less severe mutations result in a collodion membrane and congenital ichthyosiform erythroderma-like presentation. ABCA12 is an ATP binding cassette (ABC) transporter, and is a member of a large family of proteins that hydrolyze ATP to transport cargo across membranes. ABCA12 is thought to be a lipid transporter in keratinocytes necessary for lipid transport into lamellar granules during the formation of the lipid barrier.

Biopsy of skin may be done to assess the histologic characteristics of the cells. Histological findings usually reveal hyperkeratotic skin cells, which leads to a thick, white and hard skin layer.

There is no known cure for this syndrome. Patients usually need ophthalmic surgery and may also need dental surgery

Genetic counseling and screening of the mother's relatives is recommended.

An accurate diagnosis of retinitis pigmentosa relies on the documentation of the progressive loss photoreceptor cell function, confirmed by a combination of visual field and visual acuity tests, fundus and optical coherence imagery, and electroretinography (ERG),

Visual field and acuity tests measure and compare the size of the patient's field of vision and the clarity of their visual perception with the standard visual measurements associated with healthy 20/20 vision. Clinical diagnostic features indicative of retinitis pigmentosa include a substantially small and progressively decreasing visual area in the visual field test, and compromised levels of clarity measured during the visual acuity test. Additionally, optical tomography such as fundus and retinal (optical coherence) imagery provide further diagnostic tools when determining an RP diagnosis. Photographing the back of the dilated eye allows the confirmation of bone spicule accumulation in the fundus, which presents during the later stages of RP retinal degeneration. Combined with cross-sectional imagery of optical coherence tomography, which provides clues into photoreceptor thickness, retinal layer morphology, and retinal pigment epithelium physiology, fundus imagery can help determine the state of RP progression.

While visual field and acuity test results combined with retinal imagery support the diagnosis of retinitis pigmentosa, additional testing is necessary to confirm other pathological features of this disease. Electroretinography (ERG) confirms the RP diagnosis by evaluating functional aspects associated with photoreceptor degeneration, and can detect physiological abnormalities before the initial manifestation of symptoms. An electrode lens is applied to the eye as photoreceptor response to varying degrees of quick light pulses is measured. Patients exhibiting the retinitis pigmentosa phenotype would show decreased or delayed electrical response in the rod photoreceptors, as well as possibly compromised cone photoreceptor cell response.

The patient's family history is also considered when determining a diagnosis due to the genetic mode of inheritance of retinitis pigmentosa. At least 35 different genes or loci are known to cause "nonsyndromic RP" (RP that is not the result of another disease or part of a wider syndrome). Indications of the RP mutation type can be determine through DNA testing, which is available on a clinical basis for:

- (autosomal recessive, Bothnia type RP)

- (autosomal dominant, RP1)

- (autosomal dominant, RP4)

- (autosomal dominant, RP7)

- (autosomal dominant, RP13)

- (autosomal dominant, RP18)

- CRB1 (autosomal recessive, RP12)

- (autosomal recessive, RP19)

- (autosomal recessive, RP20)

For all other genes (e.g. DHDDS), molecular genetic testing is available on a research basis only.

RP can be inherited in an autosomal dominant, autosomal recessive, or X-linked manner. X-linked RP can be either recessive, affecting primarily only males, or dominant, affecting both males and females, although males are usually more mildly affected. Some digenic (controlled by two genes) and mitochondrial forms have also been described.

Genetic counseling depends on an accurate diagnosis, determination of the mode of inheritance in each family, and results of molecular genetic testing.

Treatments for ichthyosis often take the form of topical application of creams and emollient oils, in an attempt to hydrate the skin. Creams containing lactic acid have been shown to work exceptionally well in some cases. Application of propylene glycol is another treatment method. Retinoids are used for some conditions.

Exposure to sunlight may improve or worsen the condition. In some cases, excess dead skin sloughs off much better from wet tanned skin after bathing or a swim, although the dry skin might be preferable to the damaging effects of sun exposure.

There can be ocular manifestations of ichthyosis, such as corneal and ocular surface diseases. Vascularizing keratitis, which is more commonly found in congenital keratitis-ichythosis-deafness (KID), may worsen with isotretinoin therapy.

XLI can be suspected based on clinical findings, although symptoms can take varying amounts of time to become evident, from a few hours after birth, up to a year in milder cases. The diagnosis is usually made by a dermatologist, who also typically formulates the treatment plan (see below). STS enzyme deficiency is confirmed using a clinically available biochemical assay. Carrier detection can be performed in mothers of affected sons using this test (see Genetics, below). Molecular testing for DNA deletions or mutations is also offered, and can be particularly useful in the evaluation of individuals with associated medical conditions (see below). Prenatal diagnosis is possible using either biochemical or molecular tests. However, the use of prenatal diagnosis for genetic conditions that are considered to be generally benign raises serious ethical considerations and requires detailed genetic counseling.

Diagnosis can be made at birth by identifying the symptoms of the child. Ultrastructural diagnosis where tissues are analyzed is using electron microscopy is also conducted. A specimen of skin is obtained via a skin biopsy and analyzed to see any tell tale characteristics.Genetic testing can also be done to identify the mutation on the FATP4 gene associated with fatty acid synthesis. Genetic consultation through a genetic counsellor is done to determine whether the individual has this syndrome and reduces the chances of misdiagnoses with other cutaneous diseases.

The symptoms would appear at birth or shortly after birth. The combination of physical symptoms on the child would suggest they have CHILD syndrome. A skin sample examined under a microscope would suggest the characteristics of the syndrome and an X-Ray of the trunk, arms, and legs would help to detect underdeveloped bones. A CT scan would help detect problems of the internal organs.

Overheating: The scaling of the skin prevents normal sweating so hot weather and/or vigorous exercise can cause problems.

Eye problems: The eyelids can be pulled down by the tightness of the skin and this can make eyelids (but usually just the lower one) very red and they are prone to drying and irritation.

Constriction bands: Very rarely children with this condition can have tight bands of skin around their fingers or toes (usually at the tips) that can prevent proper blood circulation to the area.

Hair loss: Severe scaling of the skin on the scalp can lead to patchy loss of hair, but this is rarely permanent.

The diagnosis is usually based on clinical features present at birth.

Ultrasound in the second trimester may show abnormalities associates with NLS, including polyhydramnios, intrauterine growth restriction, microcephaly, proptosis and decreased fetal motility.

The prognosis is poor; affected individuals are either stillborn or die shortly after birth. The longest survival reported in literature is of 134 days.

This syndrome is transmitted as an autosomal recessive disorder and there is a risk for recurrence of 25% in future pregnancies.

Diagnosis can be established on clinical grounds and this may be enhanced with studies on surgically excised corneal tissue and in some cases with molecular genetic analyses. As clinical manifestations widely vary with the different entities, corneal dystrophies should be suspected when corneal transparency is lost or corneal opacities occur spontaneously, particularly in both corneas, and especially in the presence of a positive family history or in the offspring of consanguineous parents.

Superficial corneal dystrophies - "Meesmann dystrophy" is characterized by distinct tiny bubble-like, punctate opacities that form in the central corneal epithelium and to a lesser extent in the peripheral cornea of both eyes during infancy that persists throughout life. Symmetrical reticular opacities form in the superficial central cornea of both eyes at about 4–5 years of age in "Reis-Bücklers corneal dystrophy". Patient remains asymptomatic until epithelial erosions precipitate acute episodes of ocular hyperemia, pain, and photophobia. Visual acuity eventually becomes reduced during the second and third decades of life following a progressive superficial haze and an irregular corneal surface. In "Thiel–Behnke dystrophy", sub-epithelial corneal opacities form a honeycomb-shaped pattern in the superficial cornea. Multiple prominent gelatinous mulberry-shaped nodules form beneath the corneal epithelium during the first decade of life in "Gelatinous drop-like corneal dystrophy" which cause photophobia, tearing, corneal foreign body sensation and severe progressive loss of vision. "Lisch epithelial corneal dystrophy" is characterized by feather shaped opacities and microcysts in the corneal epithelium that are arranged in a band-shaped and sometimes whorled pattern. Painless blurred vision sometimes begins after sixty years of life.

Corneal stromal dystrophies - "Macular corneal dystrophy" is manifested by a progressive dense cloudiness of the entire corneal stroma that usually first appears during adolescence and eventually causing severe visual impairment. In "Granular corneal dystrophy" multiple small white discrete irregular spots that resemble bread crumbs or snowflakes become apparent beneath Bowman zone in the superficial central corneal stroma. They initially appear within the first decade of life. Visual acuity is more or less normal. "Lattice dystrophy" starts as fine branching linear opacities in Bowman's layer in the central area and spreads to the preiphery. Recurrent corneal erosions may occur. The hallmark of "Schnyder corneal dystrophy" is the accumulation of crystals within the corneal stroma which cause corneal clouding typically in a ring-shaped fashion.

Posterior corneal dystrophies - "Fuchs corneal dystrophy" presents during the fifth or sixth decade of life. The characteristic clinical findings are excrescences on a thickened Descemet membrane (cornea guttae), generalized corneal edema and decreased visual acuity. In advanced cases, abnormalities are found in the all layers of the cornea. In "posterior polymorphous corneal dystrophy" small vesicles appear at the level of Descemet membrane. Most patients remain asymptomatic and corneal edema is usually absent. "Congenital hereditary endothelial corneal dystrophy" is characterized by a diffuse ground-glass appearance of both corneas and markedly thickened (2–3 times thicker than normal) corneas from birth or infancy.

Many professionals that are likely to be involved in the treatment of those with Stickler's syndrome, include anesthesiologists, oral and maxillofacial surgeons; craniofacial surgeons; ear, nose, and throat specialists, ophthalmologists, optometrists, audiologists, speech pathologists, physical therapists and rheumatologists.

Diagnosis is based on appearance and family history. KID syndrome or keratosis follicularis spinulosa decalvans have some similar symptoms and must be eliminated.

Early stages may be asymptomatic and may not require any intervention. Initial treatment may include hypertonic eyedrops and ointment to reduce the corneal edema and may offer symptomatic improvement prior to surgical intervention.

Suboptimal vision caused by corneal dystrophy usually requires surgical intervention in the form of corneal transplantation. Penetrating keratoplasty, a common type of corneal transplantation, is commonly performed for extensive corneal dystrophy.

With penetrating keratoplasty (corneal transplant), the long-term results are good to excellent. Recent surgical improvements have been made which have increased the success rate for this procedure. However, recurrence of the disease in the donor graft may happen. Superficial corneal dystrophies do not need a penetrating keratoplasty as the deeper corneal tissue is unaffected, therefore a lamellar keratoplasty may be used instead.

Phototherapeutic keratectomy (PTK) can be used to excise or ablate the abnormal corneal tissue. Patients with superficial corneal opacities are suitable candidates for a this procedure.

As with all types of ichthyosis, there is no cure but the symptoms can be relieved.

- Moisturizers

- Prevention of overheating

- Eye drops (to prevent the eyes from becoming dried out)

- Systemic Retinoids (isotretinoin and acitretin are very effective, but careful monitoring for toxicity is required. Only severe cases may require intermittent therapy.)

Psychological therapy or support may be required as well.

Mild forms of IBS should be diagnosable from appearance and patient history alone. Severe cases of IBS are hard to distinguish from mild EHK.

A skin biopsy shows a characteristic damaged layer in the upper spinous level of the skin. Again it may be difficult to distinguish from EHK.

The gene causing IBS is known and so a definite diagnosis can be given by genetic testing.

Weissenbacher-Zweymüller syndrome is diagnosed upon a thorough clinical evaluation, detailed patient history, identification of characteristic symptom and a variety of specialized tests which includes x-rays.

A neuro-ophthalmologist is usually involved in the diagnosis and management of KSS. An individual should be suspected of having KSS based upon clinical exam findings. Suspicion for myopathies should be increased in patients whose ophthalmoplegia does not match a particular set of cranial nerve palsies (oculomotor nerve palsy, fourth nerve palsy, sixth nerve palsy). Initially, imaging studies are often performed to rule out more common pathologies. Diagnosis may be confirmed with muscle biopsy, and may be supplemented with PCR determination of mtDNA mutations.

There are no life-threatening complications after the perinatal period (around the time of birth) and the skin conditions persist but to a lesser degree of severity. Individuals have a favourable prognosis as symptoms can be managed and past the infancy stage are not life-threatening. The red skin edema improves after a three-week period but the ichthyosis scaling persists. Asthma has been recorded in some cases later on in the individual's life and sign of atopic dermatitis persist, follicular hyperkeratosis and small amounts of scaling at the scalp that goes on into adulthood but otherwise the individual continues a healthy life.

The diagnosis of Muenke syndrome is suspected bases on abnormal skull shape and a diagnosis of coronal craniosynostosis. In 2006, Agochukwu and her colleagues concluded that “A distinct Muenke syndrome phenotype includes: uni or bilateral coronal synostosis, midface hypoplasia, broad toes, and brachydactyly.” Due to phenotypic overlap and/or mild phenotypes, clinical differentiation of this syndrome may be difficult. The suspected diagnosis is confirmed by a blood test to check for gene mutation. To establish the extent of disease in an individual diagnosed with Muenke syndrome, various evaluations are recommended.

Retinitis pigmentosa is the leading cause of inherited blindness, with approximately 1/4,000 individuals experiencing the non-syndromic form of their disease within their lifetime. It is estimated that 1.5 million people worldwide are currently affected. Early onset RP occurs within the first few years of life and is typically associated with syndromic disease forms, while late onset RP emerges from early to mid-adulthood.

Autosomal dominant and recessive forms of retinitis pigmentosa affect both male and female populations equally; however, the less frequent X-linked form of the disease affects male recipients of the X-linked mutation, while females usually remain unaffected carriers of the RP trait. The X-linked forms of the disease are considered severe, and typically lead to complete blindness during later stages. In rare occasions, a dominant form of the X-linked gene mutation will affect both males and females equally.

Due to the genetic inheritance patterns of RP, many isolate populations exhibit higher disease frequencies or increased prevalence of a specific RP mutation. Pre-existing or emerging mutations that contribute to rod photoreceptor degeneration in retinitis pigmentosa are passed down through familial lines; thus, allowing certain RP cases to be concentrated to specific geographical regions with an ancestral history of the disease. Several hereditary studies have been performed to determine the varying prevalence rates in Maine (USA), Birmingham (England), Switzerland (affects 1/7000), Denmark (affects 1/2500), and Norway. Navajo Indians display an elevated rate of RP inheritance as well, which is estimated as affecting 1 in 1878 individuals. Despite the increased frequency of RP within specific familial lines, the disease is considered non-discriminatory and tends to equally affect all world populations.

It is not necessary to biopsy an ocular muscle to demonstrate histopathologic abnormalities. Cross-section of muscle fibers stained with Gömöri trichrome stain is viewed using light microscopy. In muscle fibers containing high ratios of the mutated mitochondria, there is a higher concentration of mitochondria. This gives these fibers a darker red color, causing the overall appearance of the biopsy to be described as "ragged red fibers. Abnormalities may also be demonstrated in muscle biopsy samples using other histochemical studies such as mitochondrial enzyme stains, by electron microscopy, biochemical analyses of the muscle tissue (ie electron transport chain enzyme activities), and by analysis of muscle mitochondrial DNA. "

Genetic changes are related to the following types of Stickler syndrome:

- Stickler syndrome, COL2A1 (75% of Stickler cases)

- Stickler syndrome, COL11A1

- Stickler syndrome, COL11A2 (non-ocular)

- Stickler syndrome, COL9A1 (recessive variant)

Whether there are two or three types of Stickler syndrome is controversial. Each type is presented here according to the gene involved. The classification of these conditions is changing as researchers learn more about the genetic causes.

Constant care is required to moisturise and protect the skin. The hard outer layer eventually peels off, leaving the vulnerable inner layers of the dermis exposed. Early complications result from infection due to fissuring of the hyperkeratotic plates and respiratory distress due to physical restriction of chest wall expansion.

Management includes supportive care and treatment of hyperkeratosis and skin barrier dysfunction. A humidified incubator is generally used. Intubation is often required until nares are patent. Nutritional support with tube feeds is essential until eclabium resolves and infants can begin nursing. Ophthalmology consultation is useful for the early management of ectropion, which is initially pronounced and resolves as scale is shed. Liberal application of petrolatum is needed multiple times a day. In addition, careful debridement of constrictive bands of hyperkeratosis should be performed to avoid digital ischemia. Cases of digital autoamputation or necrosis have been reported due to cutaneous constriction bands. Relaxation incisions have been used to prevent this morbid complication.

In the past, the disorder was nearly always fatal, whether due to dehydration, infection (sepsis), restricted breathing due to the plating, or other related causes. The most common cause of death was systemic infection and sufferers rarely survived for more than a few days. However, improved neonatal intensive care and early treatment with oral retinoids, such as the drug Isotretinoin (Isotrex), may improve survival. Early oral retinoid therapy has been shown to soften scales and encourage desquamation. After as little as two weeks of daily oral isotretinoin, fissures in the skin can heal, and plate-like scales can nearly resolve. Improvement in the eclabium and ectropion can also be seen in a matter of weeks. Children who survive the neonatal period usually evolve to a less severe phenotype, resembling a severe congenital ichthyosiform erythroderma. Patients continue to suffer from temperature dysregulation and may have heat and cold intolerance. Patients can also have generalized poor hair growth, scarring alopecia, contractures of digits, arthralgias, failure to thrive, hypothyroidism, and short stature. Some patients develop a rheumatoid factor-positive polyarthritis. Survivors can also develop fish-like scales and retention of a waxy, yellowish material in seborrheic areas, with ear adhered to the scalp.

The oldest known survivor is Nusrit "Nelly" Shaheen, who was born in 1984 and is in relatively good health as of April 2016. Lifespan limitations have not yet been determined with the new treatments.

A study published in 2011 in the Archives of Dermatology concluded, "Harlequin ichthyosis should be regarded as a severe chronic disease that is not invariably fatal. With improved neonatal care and probably the early introduction of oral retinoids, the number of survivors is increasing."