A 2014 study classified cases into three types—epidermolysis bullosa simplex (EBS), junctional epidermolysis bullosa (JEB), and dystrophic epidermolysis bullosa (DEB) -- and reviewed their times of death. The first two types tended to die in infancy and the last in early adulthood.

Immunoprecipitation, immunoblotting and enzyme-link immunosorbent assay (ELISA)

Poot et al. 2013 determined that immunoprecipitation for antibodies against envoplakin and periplakin or alpha2-macroglobulin-like–1 is the most sensitive test. However, alpha2-macroglobulin-like-1 can also be detected in patients with toxic epidermal necrosis.

Patients with high concentration of antibodies show intercellular, intraepidermal antibodies as well as along the dermoepidermal junction. Patients with low concentration of antibodies only present with them inside the cells (intercellular).

If the results are negative, perform the additional assays regardless. Cases have been confirmed that reported with initial negative DIF and IDIF tests.

Some patients have a few or no histopathologic abnormalities. Histological examination of a biopsy may show an increase in the number and size of capillaries and veins (rarely lymphatics), dilated capillaries located in the deeper dermis, and hyperplasia and swollen endothelial cells with occasional dilated veins and venous lakes.

Epidermolysis bullosa can be diagnosed either by a skin (punch) biopsy at the edge of a wound with immunofluorescent mapping, or via blood sample and genetic testing.

Due to the rarity of different types of vascular conditions, angiokeratomas may be misdiagnosed. A biopsy of the lesion can produce a more accurate diagnosis.

-The plaques are characterized histologically by hyperkeratosis which is a thickening of the outer layer of skin. Hyperkeratosis is often associated with an abnormal amount of keratin production. Also characteristic is moderate acanthosis a thickening of the stratum spinosum with elongation of rete ridges.

- Characteristic histologic feature is regular alternation of slightly raised parakeratotic areas without a granular layer (hypogranulosis) and slightly depressed orthokeratotic areas with prominent granular layer (hypergranulosis). Orthokeratotic hyperkeratosis is characterised by hyperkeratosis with non-nucleated cells. Parakeratotic hyperkeratosis is characterised by hyperkeratosis with nucleated cells.

- The orthokeratotic area shows a basket-weave-pattern.

- The dermis shows scattering of chronic inflammatory infiltrate (Munro's microabscess) sometimes giving a spongiform appearance.

This is very similar to linear psoriasis, but it has been noted that the diseases are distinct entities by immunohistochemical analyses.

NL is diagnosed by a skin biopsy, demonstrating superficial and deep perivascular and interstitial mixed inflammatory cell infiltrate (including lymphocytes, plasma cells, mononucleated and multinucleated histiocytes, and eosinophils) in the dermis and subcutis, as well as necrotising vasculitis with adjacent necrobiosis and necrosis of adnexal structures. Areas of necrobiosis are often more extensive and less well defined than in granuloma annulare. Presence of lipid in necrobiotic areas may be demonstrated by Sudan stains. Cholesterol clefts, fibrin, and mucin may also be present in areas of necrobiosis. Depending on the severity of the necrobiosis, certain cell types may be more predominant. When a lesion is in its early stages, neutrophils may be present, whereas in later stages of development lymphocytes and histiocytes may be more predominant.

Reported treatments include topical agents, dermabrasion, cryotherapy, laser therapy, and surgical excision. These therapies have a high failure rate because of incomplete relief of symptoms, scarring, or recurrence .

Though similar in appearance, ILVEN will not respond to therapies known to affect psoriasis. ILVEN can be very difficult to live with but can be treated. The most effective method is full-thickness excision of the lesion. CO2 Laser Surgery can resurface the skin to give a flat, smoother and more normal appearance, but does not remove the lesion.

Patients may be ashamed or actively attempt to disguise their symptoms. This can make diagnosis difficult as symptoms are not always immediately obvious, or have been deliberately hidden to avoid disclosure. If the patient admits to hair pulling, diagnosis is not difficult; if patients deny hair pulling, a differential diagnosis must be pursued. The differential diagnosis will include evaluation for alopecia areata, iron deficiency, hypothyroidism, tinea capitis, traction alopecia, alopecia mucinosa, thallium poisoning, and loose anagen syndrome. In trichotillomania, a hair pull test is negative.

A biopsy can be performed and may be helpful; it reveals traumatized hair follicles with perifollicular hemorrhage, fragmented hair in the dermis, empty follicles, and deformed hair shafts (trichomalacia). Multiple catagen hairs are typically seen. An alternative technique to biopsy, particularly for children, is to shave a part of the involved area and observe for regrowth of normal hairs.

The prognosis is favorable in most patients with an isolated cutaneous abnormality. In the majority of cases, both the vivid red marking and the difference in circumference of the extremities regress spontaneously during the first year of life. It is theorized that this may be due to the normal maturation process, with thickening of the epidermis and dermis. Improvements for some patients can continue for up to 10 years, while in other cases, the marbled skin may persist for the patient's lifetime.

One study reported an improvement in lesions in 46% of patients within 3 years. If CMTC persists into adulthood, it can result in complaints due to paresthesia, increased sensitivity to cold and pain, and the formation of ulcers.

Few reports included long-term follow up of CMTC into adolescence and adulthood. While about 50% of patients seem to show definite improvement in the reticular vascular pattern, the exact incidence and cause of persistent cases are unknown.

Outpatient treatments such as interventional radiology, lasers, and physical therapy are employed to reduce the severity of the vascular lesions. However, in some cases lasers have caused a reaction in the tissue causing it to expand and become exposed to infection. Excision and grafting may be necessary to remove the lesion. Recovery time on such an operation ranges from 3 to 12 weeks depending on location of the graft, healing time and the possibility of complications.

Diagnostic techniques:

- antibodies (IgG) precipitates complement (C3) in the lamina lucida of the basement membrane.

- Circulating auto-antibodies to BP-1 antigen (located in hemidesmosome). 50% have BP-2.

- Positive Nikolsky sign.

- IgG, C3 deposition at BM creating smooth line in immunofluorescent analysis.

Urbach–Wiethe disease is typically diagnosed by its clinical dermatological manifestations, particularly the beaded papules on the eyelids. Doctors can also test the hyaline material with a periodic acid-Schiff (PAS) staining, as the material colors strongly for this stain.

Immunohistochemical skin labeling for antibodies for the ECM1 protein as labeling has been shown to be reduced in the skin of those affected by Urbach–Wiethe disease. Staining with anti-type IV collagen antibodies or anti-type VII collagen antibodies reveals bright, thick bands at the dermoepidermal junction.

Non-contrast CT scans can image calcifications, but this is not typically used as a means of diagnosing the disease. This is partly due to the fact that not all Urbach-Wiethe patients exhibit calcifications, but also because similar lesions can be formed from other diseases such as herpes simplex and encephalitis. The discovery of mutations within the ECM1 gene has allowed the use of genetic testing to confirm initial clinical diagnoses of Urbach–Wiethe disease. It also allows doctors to better distinguish between Urbach–Wiethe disease and other similar diseases not caused by mutations in ECM1.

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.

Primary diagnosis usually starts off with a thorough physical exam and evaluation of medical history. To further investigate, a dermoscope, a diagnostic tool, is used by the dermatologist to examine the skin using a magnified lens. A complete blood count (CBC) along with other blood tests can also be done to rule out any sort of other infections. Lastly, a skin biopsy test may be ordered to arrive at a definitive diagnosis. This pathological examination of the skin biopsy helps to arrive at the correct diagnosis via a fungal culture(mycology). The biopsy is put together with clinical and microscope findings and study of the special tissues if need be. The signs and symptoms of MG are similar to many other clinical conditions and therefore it is necessary to perform all of the additional tests in order for a physician to correctly rule out all other possible diagnoses.

Clinical diagnosis can be made with the naked eye using the ABCD guideline or by using dermatoscopy. An online-screening test is also available to help screen out benign moles.

There is no clearly defined cure for necrobiosis. NLD may be treated with PUVA therapy and improved therapeutic control.

Although there are some techniques that can be used to diminish the signs of necrobiosis such as low dose aspirin orally, a steroid cream or injection into the affected area, this process may be effective for only a small percentage of those treated.

The physical examination of the skin and its appendages, as well as the mucous membranes, forms the cornerstone of an accurate diagnosis of cutaneous conditions. Most of these conditions present with cutaneous surface changes termed "lesions," which have more or less distinct characteristics. Often proper examination will lead the physician to obtain appropriate historical information and/or laboratory tests that are able to confirm the diagnosis. Upon examination, the important clinical observations are the (1) morphology, (2) configuration, and (3) distribution of the lesion(s). With regard to morphology, the initial lesion that characterizes a condition is known as the "primary lesion," and identification of such a lesions is the most important aspect of the cutaneous examination. Over time, these primary lesions may continue to develop or be modified by regression or trauma, producing "secondary lesions." However, with that being stated, the lack of standardization of basic dermatologic terminology has been one of the principal barriers to successful communication among physicians in describing cutaneous findings. Nevertheless, there are some commonly accepted terms used to describe the macroscopic morphology, configuration, and distribution of skin lesions, which are listed below.

In the earlier stages of actinic elastosis, elastic fiber proliferation can be seen in the dermis. As the condition becomes more established, the collagen fibers of the papillary dermis and reticular dermis become increasingly replaced by thickened and curled fibers that form tangled masses and appear basophilic under routine haematoxylin and eosin staining. These fibers stain black with the Verhoeff stain.

The diagnostic testing for vasculitis should be guided by the patient's history and physical exam. The clinician should ask about the duration, onset, and presence any associated symptoms such as weight loss or fatigue (that would indicate a systemic cause). It is important to distinguish between IgA and non-IgA vasculitis. IgA vasculitis is more likely to present with abdominal pain, bloody urine, and joint pain. In the case that the cause is not obvious, a reasonable initial workup would include a complete blood count, urinalysis, basic metabolic panel, fecal occult blood testing, erythrocyte sedimentation rate (ESR), and C-reactive protein level. Small vessel cutaneous vasculitis is a diagnosis of exclusion and requires ruling out systemic causes of the skin findings. Skin biopsy (punch or excisional) is the most definitive diagnostic test and should be performed with 48 hours of appearance of the vasculitis. A skin biopsy will be able to determine if the clinical findings are truly due to a vasculitis or due to some other cause.

The scleredema is usually proposed as a diagnosis based on the appearance of the skin and the patient's medical history. To confirm the diagnosis, the doctor performs a skin biopsy, in which hematoxylin and eosin staining will show a thick reticular dermis with thick collagen bundles separated by clear spaces. The patient's blood may be examined for diseases that may appear after the onset of symptoms, such as multiple myeloma.

Diagnosis is made by clinical observation and the following tests.

(1) Gram stain of the fluid from pustules or bullae, and tissue swab.

(2) Blood culture

(3) Urine culture

(4) Skin biopsy

(5) Tissue culture

Magnetic resonance imaging can be done in case of ecthyma gangrenosum of plantar foot to differentiate from necrotizing fasciitis.

Numerous treatment options are available for photoaged skin, including dermabrasion, topical application of retinoic acid, carbon dioxide laser resurfacing, hyaluronic acid injection into the dermis, imiquimod, tacrolimus ointment, and topical oestrogen therapy. These treatments have variable efficacy.

The most effective prevention strategy for photoaging remains minimization of sun exposure, through use of sunscreen and other sun exposure avoidance measures.

Melasma is usually diagnosed visually or with assistance of a Wood's lamp (340 - 400 nm wavelength). Under Wood's lamp, excess melanin in the epidermis can be distinguished from that of the dermis.