The diagnosis of IP is established by clinical findings and occasionally by corroborative skin biopsy. Molecular genetic testing of the NEMO IKBKG gene (chromosomal locus Xq28) reveals disease-causing mutations in about 80% of probands. Such testing is available clinically.

In addition, females with IP have skewed X-chromosome inactivation; testing for this can be used to support the diagnosis.

Many people in the past were misdiagnosed with a second type of IP, formerly known as IP1. This has now been given its own name - 'Hypomelanosis of Ito' (incontinentia pigmenti achromians). This has a slightly different presentation: swirls or streaks of hypopigmentation and depigmentation. It is "not" inherited and does not involve skin stages 1 or 2. Some 33–50% of patients have multisystem involvement — eye, skeletal, and neurological abnormalities. Its chromosomal locus is at Xp11, rather than Xq28.

MDM is most common on the Dalmatian island of Mljet (or "Meleda"), thought to be because of a founder effect. It is of autosomal recessive inheritance. It may be caused by a mutation on the "SLURP1" gene, located on chromosome 8.

Meleda disease (MDM) or "mal de Meleda", also called Mljet disease, keratosis palmoplantaris and transgradiens of Siemens, (also known as "Acral keratoderma," "Mutilating palmoplantar keratoderma of the Gamborg-Nielsen type," "Palmoplantar ectodermal dysplasia type VIII", and "Palmoplantar keratoderma of the Norrbotten type") is an extremely rare autosomal recessive congenital skin disorder in which dry, thick patches of skin develop on the soles of the hands and feet, a condition known as palmoplantar hyperkeratosis.

Treatment of manifestations: special hair care products to help manage dry and sparse hair; wigs; artificial nails; emollients to relieve palmoplantar hyperkeratosis.

There does not yet exist a specific treatment for IP. Treatment can only address the individual symptoms.

Usually, a common form of treatment for the condition is a type of hand cream which moisturises the hard skin. However, currently the condition is incurable.

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.

Epidermodysplasia verruciformis (EV), also known as treeman syndrome, is an extremely rare autosomal recessive hereditary skin disorder associated with a high risk of skin cancer. It is characterized by abnormal susceptibility to human papillomaviruses (HPVs) of the skin. The resulting uncontrolled HPV infections result in the growth of scaly macules and papules, particularly on the hands and feet. It is typically associated with HPV types 5 and 8, which are found in about 80% of the normal population as asymptomatic infections, although other types may also contribute.

The condition usually has an onset of between the ages of one and 20 but can occasionally present in middle age. The condition is also known as Lewandowsky–Lutz dysplasia – named after the physicians who first documented it, Felix Lewandowsky and Wilhelm Lutz.

Erythrokeratodermia variabilis (also known as "erythrokeratodermia figurata variabilis", "keratosis extremitatum progrediens", "keratosis palmoplantaris transgrediens et progrediens", "Mendes da Costa syndrome", "Mendes da Costa type erythrokeratodermia", and "progressive symmetric erythrokeratoderma") is a rare autosomal dominant disorder that usually presents at birth or during the first year of life. To date, it is thought to be caused by mutations in genes encoding for connexin channels proteins in the epidermis, leading to the misregulation of homeostasis in keratinocytes.

One type is characterized by generalized, persistent, brown hyperkeratosis with accentuated skin markings, while a second type is localized, with involvement that is limited in extent and characterized by sharply demarcated, hyperkeratotic plaques.

It can be associated with GJB3 and GJB4.

It was characterized in 1925.

Patient presents with the following signs.

1. Hyperkeratotic papules present over the seborrheic area of the body.

2. V - shaped nicking present at the tip of the nails.

3. Red and white longitudinal nail lines.

HED2 is suspected after infancy on the basis of physical features in most affected individuals. GJB6 is the only gene known to be associated with HED2. Targeted mutation analysis for the four most common GJB6 mutations is available on a clinical basis and detects mutations in approximately 100% of affected individuals. Sequence analysis is also available on a clinical basis for those in whom none of the four known mutations is identified.

No curative treatment against EV has been found yet. Several treatments have been suggested, and acitretin 0.5–1 mg/day for 6 months’ duration is the most effective treatment owing to antiproliferative and differentiation-inducing effects.

Interferons can also be used effectively together with retinoids.

Cimetidine was reported to be effective because of its depressing mitogen-induced lymphocyte proliferation and regulatory T cell activity features. A report by Oliveira "et al." showed that cimetidine was ineffective. Hayashi "et al." applied topical calcipotriol to a patient with a successful result.

As mentioned, various treatment methods are offered against EV; however, most importantly, education of the patient, early diagnosis, and excision of the tumoral lesions take preference to prevent the development of cutaneous tumors.

The differential diagnosis is quite extensive and includes

- Buschke–Fischer–Brauer disease

- Curth–Macklin ichthyosis

- Gamborg Nielsen syndrome

- Greither disease

- Haber syndrome

- Hereditary punctate palmoplantar keratoderma

- Jadassohn–Lewandowsky syndrome

- Keratosis follicularis spinulosa decalvans

- Keratosis linearis with ichthyosis congenital and sclerosing keratoderma syndrome

- Meleda disease

- Mucosa hyperkeratosis syndrome

- Naegeli–Franceschetti–Jadassohn syndrome

- Naxos disease

- Olmsted syndrome

- Palmoplantar keratoderma and leukokeratosis anogenitalis

- Pandysautonomia

- Papillomatosis of Gougerot and Carteaud

- Papillon–Lefèvre syndrome

- Punctate porokeratotic keratoderma

- Richner–Hanhart syndrome

- Schöpf–Schulz–Passarge syndrome

- Unna Thost disease

- Vohwinkel syndrome

- Wong's dermatomyositis

CCCA tends to present itself in the 20s and progresses over 20–30 years. One should consider this diagnosis in African Americans with what appears to be a female-pattern hair loss.

Treatments for CCCA remain investigational. Altering hair care practices has not been proven to assist in hair rejuvenation. High-dose topical steroids, antibiotics, immunomodulators such as tacrolimus (Protopic) and pimecrolimus (Elidel), and anti-androgen/5alpha Reductase inhibitors have been used with unknown efficacy.

Keratosis follicularis spinulosa decalvans (also known as "Siemens-1 syndrome") is a rare X-linked disorder described by Siemens in 1926, a disease that begins in infancy with keratosis pilaris localized on the face, then evolves to more diffuse involvement.

An association with SAT1 has been suggested.

Monilethrix (also referred to as beaded hair) is a rare autosomal dominant hair disease that results in short, fragile, broken hair that appears beaded. It comes from the Latin word for necklace ("monile") and the Greek word for hair ("thrix").

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

Palmoplantar keratodermas are a heterogeneous group of disorders characterized by abnormal thickening of the palms and soles.

Autosomal recessive and dominant, X-linked, and acquired forms have all been described.

Howel–Evans syndrome is an extremely rare condition involving thickening of the skin in the palms of the hands and the soles of the feet (hyperkeratosis). This familial disease is associated with a high lifetime risk of esophageal cancer. For this reason, it is sometimes known as tylosis with oesophageal cancer (TOC).

The condition is inherited in an autosomal dominant manner, and it has been linked to a mutation in the "RHBDF2" gene. It was first described in 1958.

There is no cure for IBS but in the future gene therapy may offer a cure.

Treatments for IBS generally attempt to improve the appearance of the skin and the comfort of the sufferer. This is done by exfoliating and increasing the moisture of the skin. Common treatments include:

- Emollients: moisturisers, petroleum jelly or other emolients are used, often several times a day, to increase the moisture of the skin.

- Baths: long baths (possibly including salt) several times a week are used to soften the skin and allow exfoliation.

- Exfoliating creams: creams containing keratolytics such as urea, salicylic acid and lactic acid may be useful.

- Antiseptic washes: antiseptics may be used to kill bacteria in the skin and prevent odour.

- Retenoids: very severe cases may use oral retinoids to control symptoms but these have many serious side effects including, in the case of IBS, increased blistering.

Focal palmoplantar and gingival keratosis is a rare autosomal dominant disease whose clinical features, and in particular, pathologic alterations and molecular mechanisms remains to be well defined.

The presentation may be of alopecia (baldness). Individuals vary in severity of symptoms. Nail deformities may also be present as well as hair follicle keratosis and follicular hyperkeratosis.

Dermoscopy is a noninvasive technique utilizing a handheld magnifying device coupled with a transilluminating lift. It is often used in the evaluation of cutaneous lesions, but lacks the definitive diagnostic ability of biopsy-based tissue diagnosis. Histopathologic exam remains the gold standard

A lesion biopsy is performed if the diagnosis remains uncertain after a clinical physical exam. The most common tissue sampling techniques include shave or punch biopsy. When only a portion of the lesion can be removed due to its size or location, the biopsy should sample tissue from the thickest area of the lesion, as SCCs are most likely to be detected in that area. If a shave biopsy is performed, it should extend through to the level of the dermis in order to provide sufficient tissue for diagnosis; ideally, it would extend to the mid-reticular dermis. Punch biopsy usually extends to the subcutaneous fat when the entire length of the punch blade is utilized.