Psoriasis: Manifestations, Management, and Mimics
Psoriasis is a chronic, noncontagious, multifactorial inflammatory skin condition that has several subtypes. The five major forms are plaque, inverse, guttate, erythrodermic, and pustular psoriasis.[1-6] The classic lesion is a pink plaque topped with a micaceous (mica-like) scale (shown).[1] Forcible removal of these scales may cause pinpoint bleeding (Auspitz sign).[2] Psoriasis can affect any age group but primarily occurs in those 15-35 and 50-60 years of age.[1,3-6] Therapy is based on the psoriasis subtype, site and size of the area(s) involved, and severity of the eruption.[1] Although the immune system is involved, particularly T cells, and some patients have a genetic predisposition, many unknowns remain about what factors trigger its onset, cause a flare, and determine the extent and particular pattern.
Psoriasis: Manifestations, Management, and Mimics
Plaque Psoriasis
Plaque psoriasis (psoriasis vulgaris) is the most common subtype of psoriasis.[2,5] Although it may occur anywhere on the body, some areas are classically affected (eg, knees, elbows, lower back) (shown).[1,5,6] The plaques may be pruritic or feel sore, or they may be asymptomatic. The face is rarely involved, and sun-exposed areas of the arms may also be relatively spared. Phototherapy is an effective therapeutic option.[1,5,6] As the condition is treated and improves, the scales may mostly regress and leave the pink plaques behind, which eventually flatten to a pink patch. Discoloration of skin at the site of a treated plaque may be persistent. Systemic steroids may lead to rapid clearing of psoriasis but should not be used, because if they are abruptly discontinued, a limited plaque psoriasis may blossom into potentially life-threatening generalized pustular or erythrodermic psoriasis.
Psoriasis: Manifestations, Management, and Mimics
In White patients, psoriasis usually consists of pink to red lesions. However, as is the case with many other inflammatory conditions, the lesions may have a dusky violaceous (purple) appearance on individuals with darker skin, especially in those with an African background. Treatment for psoriasis may be the same for any skin type; however, strong topical corticosteroids have a pigment-bleaching effect that may cause the skin defect to be more noticeable on dark-skinned persons, even if the psoriasis itself is responding to therapy.
Psoriasis: Manifestations, Management, and Mimics
Inverse Psoriasis
Inverse psoriasis affects areas with skin folds (retroauricular [center], axillary [right], inframammary, abdominal, inguinal, and genital sites). It usually has much less scaling than typical plaque type psoriasis and is often mistaken for a fungal infection or a skin allergy. It will usually respond to topical or systemic therapy.[1,5,6] However, some topical treatments may cause skin irritation, and long-term use of strong corticosteroids in skin folds may result in skin thinning and striae formation.[1,6]
Genital psoriasis (left) appears pink or red, with relatively thin plaques and little/no scale. Potent topical corticosteroids may be needed to clear the lesions. Consider biopsy for atypical lesions or persistent plaques to exclude squamous cell carcinoma or extramammary Paget disease. Empiric therapy before biopsy is usually acceptable if psoriasis is present in other body areas; in particular, the presence of "gluteal pinkening" supports the diagnosis of psoriasis in patients with equivocal findings elsewhere on the skin.
Psoriasis: Manifestations, Management, and Mimics
Guttate (Eruptive) Psoriasis
Guttate ("drop-like" or eruptive) psoriasis is the second most common subtype of psoriasis, accounting for about 8% of cases.[3] It is often seen in younger patients (children, young adults)[3] and may present as a relatively sudden worsening of a preexisting plaque psoriasis or as the first and only manifestation of psoriasis.[3,6] Coexisting infections (eg, with Streptococcus pyogenes) may trigger the disease.[1,3,6] Some clinicians may initiate empiric therapy for group A streptococcal infection when they start to treat the skin eruption, which is characterized by dozens to hundreds of small pink papules topped with a fleck of psoriatic scale (shown). These lesions tend to itch more than other forms of psoriasis and so may be confused with other rashes (eg, drug eruptions, pityriasis rosea). In guttate psoriasis, the area of involvement is usually much more extensive than can be managed with topical therapy alone. However, this disease responds especially well to ultraviolet (UV) phototherapy and, when that is not practical or available, to natural sunlight.
Psoriasis: Manifestations, Management, and Mimics
Erythrodermic Psoriasis
Erythrodermic ("red skin" or exfoliative) psoriasis, a rare (about 3% of psoriasis patients) and potentially life-threatening condition, is characterized by widespread erythema and scaling of the skin.[1,3,6] It may result from refractory or untreated psoriasis, or it may be induced by severe sunburns or medications as well as withdrawal from oral corticosteroids.[1,3] Patients are often febrile, have an elevated white blood cell (WBC) count, and suffer generalized malaise. Due to increased shunting of blood to the skin, patients may become hypothermic and hypotensive; older patients with more fragile cardiovascular systems may go into high-output cardiac failure. In more chronic cases, an increased skin metabolism and turnover rate can cause nutritional difficulties.[3] Patients often require hospitalization, especially if they are older or have comorbid conditions. The differential diagnosis includes severe drug eruptions, cutaneous T-cell lymphoma, pityriasis rubra pilaris, and severe seborrheic dermatitis (which may be associated with progressive human immunodeficiency virus infection). Treatment is supportive and may include topical or systemic agents.[3]
Psoriasis: Manifestations, Management, and Mimics
Pustular Psoriasis
Pustular psoriasis is a potentially life-threatening condition that has two primary variations: Von Zumbusch is the generalized form (right), whereas acrodermatitis continua of Hallopeau affects the hands and feet (left). The generalized type is mainly seen in adults; it is characterized by lakes of sterile pus and reddened skin that often itch and burn.[3] The disease may present alone, or with plaque psoriasis at other sites. Patients may have disabling malaise, elevated WBC count, and fever,[6,7] which may be misinterpreted as evidence of infection. Triggers may include drugs, the abrupt withdrawal of systemic corticosteroids, and infectious or chemical exposure.[1,3] Generalized pustular psoriasis usually requires hospitalization for supportive care and systemic therapy, as the affected sites are usually too large to manage with topical medications alone.
Psoriasis: Manifestations, Management, and Mimics
Acrodermatitis Continua
Unlike patients with Von Zumbusch pustular psoriasis, patients with pustular psoriasis of the palms and soles are less likely to have generalized signs/symptoms, although they may have severe pruritus. Triggers include local trauma or infection.[3,7] Even with relatively limited involvement of the total body surface area, involvement of the feet may make walking difficult and involvement of the hands, including infections of deep fissures that may occur in severe disease (shown), may make patients incapacitated. Bacterial culture and organism-specific antibiotics may sometimes be necessary. Avoidance of open wounds and fissures is especially important in patients who are on long-term immunosuppressive medications. Topical therapies may be tried but may have limited penetration through thicker acral skin and the lakes of pus. Thus, severe acral psoriasis may be best treated with systemic therapy.
Psoriasis: Manifestations, Management, and Mimics
Scalp Psoriasis
At least 50% of patients with psoriasis have scalp involvement,[3] and it may be their only psoriatic manifestation. The disease may involve the entire scalp, or be localized (eg, occiput; periauricular or anterior hairline, sometimes extending onto the forehead [left]).[3] Psoriasis and seborrhea features may overlap; the term "sebopsoriasis" describes the widespread red plaques and thick scaling on the scalp, and patients may have self-diagnosed their condition as particularly bad dandruff (seborrheic dermatitis). Many of the same treatments will help both conditions; however, pretreatment use of salicylic acid shampoo or peanut oil or other keratolytics may help to remove/loosen scales and improve the penetration of topical agents (eg, topical corticosteroids, tar shampoos). Systemic therapies may be needed for adequate control of scalp involvement, especially in patients who cannot or will not wear their hair shorter. The image on the right shows partially treated scalp psoriasis.
Psoriasis: Manifestations, Management, and Mimics
Shaving the head to allow better application of medications may cause problems in and of itself. In what may be thought of as scalp koebnerization (the development of lesions at sites of trauma), patients with active or latent psoriasis may find that a close haircut or other hair treatments is followed by a natural spiking of the hair known as "the tee-pee sign" (shown). This sign has also been seen in individuals with severe seborrhea, but even subtle scalp inflammation in psoriasis can induce this growth pattern after relatively minor scalp trauma.
Psoriasis: Manifestations, Management, and Mimics
Psoriatic Nails
Psoriasis may affect fingernails and toenails; this may be the only expression of psoriasis in some patients. Psoriatic nails may be indistinguishable from onychomycosis and, due to the presence of subungual debris and onycholysis, they may be more susceptible to fungal infection than normal nails. A combination of "oil spots" (yellow to brown discolorations under the nail plate) (left), small pits on the nail surface, distal onycholysis (center), and subungual debris may be present. Systemic medications are often more effective than topical agents. Alternatively, corticosteroid injection (eg, triamcinolone) directly into the proximal nail fold (right) may be reasonable if only a limited number of nails are affected. Although the injections can be painful, they may improve inflammation and, ultimately, nail appearance. Existing nail deformity cannot be undone quickly. Complete replacement of a fingernail may take 6-9 months, and of a big toenail, approximately 12-18 months. Some studies suggest that patients with refractory hand psoriasis and severe nail involvement may be more likely to develop psoriatic arthritis, especially in the distal interphalangeal joints.[8]
Psoriasis: Manifestations, Management, and Mimics
Psoriasis may also be associated with other conditions (eg, arthritis, cardiovascular disease, diabetes, depression).[3] Psoriatic arthritis (shown) may occur in up to 30% of patients with psoriasis.[2,4] Psoriatic arthritis tends to preferentially affect smaller joints rather than the axial skeleton. This condition can be progressive and crippling, and it may coexist with other types of arthritis. Many of the systemic medications prescribed for psoriasis also help in the management of psoriatic arthritis and vice versa. However, the use of nonsteroidal anti-inflammatory drugs (NSAIDs) such as ibuprofen or naproxen to manage arthritis may cause skin psoriasis flares in some patients.
Psoriasis: Manifestations, Management, and Mimics
Koebner Phenomenon
The Koebner phenomenon is seen in a variety of inflammatory skin conditions, including psoriasis. It involves relatively minor trauma inducing the onset of an underlying skin condition in the area of injury. In psoriasis, triggers of Koebner phenomenon include scratches (right), abrasions, minor burns, and surgical procedures. Caution patients with active psoriatic disease to avoid unnecessary decorative skin trauma such as tattoos and body piercings. Although UV light is generally beneficial for most forms of psoriasis, another expression of the Koebner phenomenon may be sunburns, which can cause a severe flare (left; center).
Sources of image data: National Psoriasis Foundation[3] and American Academy of Dermatology.[6]
Psoriasis: Manifestations, Management, and Mimics
Treatment
No cure for psoriasis currently exists, but different treatment modalities may be used to ameliorate signs/symptoms of the disease and improve quality of life. Every patient is unique not only in the severity and distribution of their psoriasis but also in their response to therapy, so all treatment should be personalized.[3,6]
Topical corticosteroids remain the mainstay of therapy for most patients with mild, limited, or early psoriasis[1,3,9,10]; these agents are also used to manage flares and resistant areas in those on systemic therapy. Therapeutic phototherapy is useful for patients with widespread psoriasis (ie, moderate to severe disease) who also have medical comorbidities. It generally involves UV light: either UVB or UVA following psoralen sensitization (psoralen plus UVA [PUVA]).[1,3,6,11] Systemic therapy includes disease-modifying antirheumatic drugs (DMARDs; eg, cyclosporine, methotrexate) and biologic agents,[1,6,12] as well as other medications such as acitretin and apremilast.[1,3,6,13]
Psoriasis: Manifestations, Management, and Mimics
Diagnostic Dilemmas
Psoriasis may be missed or misdiagnosed. Therapy can change the appearance of lesions and, sometimes, cause confusing histologic findings on biopsies. Many inflammatory, infectious, and neoplastic skin conditions may present as "red, scaly rings"; most will improve or temporarily seem to improve with topical steroid use. By the time patients see clinicians, most have tried to self-treat with over-the-counter (OTC) antifungal agents and leftover creams previously prescribed to them for other reasons or borrowed from others. Some will have tried various domestic/overseas Internet products, which may contain significant amounts of potent steroids.
The image is from a typical patient who unsuccessfully self-treated her "ringworm" with an OTC antifungal. Subsequently, a prescription combination antifungal/corticosteroid seemed very effective. Although the morphology of the red rings is suggestive of tinea corporis, the lack of response to the initial self-therapy and the better response to the prescribed agent suggest that the corticosteroid was the effective component. The diagnosis of psoriasis is most likely with similar findings on the elbows and early psoriatic nail changes.
Psoriasis: Manifestations, Management, and Mimics
Chronic contact dermatitis (top left) and chronic hand eczema (bottom left) may resemble psoriasis. In fact, biopsies of these skin lesions may sometimes be interpreted as "psoriasiform dermatitis" (ie, even microscopically, the lesions look like psoriasis). Many psoriasis treatments (eg, topical corticosteroids, systemic immunosuppressive agents) may effectively treat chronic contact dermatitis and chronic hand eczema. However, other psoriasis treatment options (eg, topical retinoids, vitamin D analogues) may irritate the skin and exacerbate both conditions.
Crusted scabies (right) may resemble psoriasis of the hands, scalp, and body; in severe cases, it may even mimic erythrodermic psoriasis. Topical corticosteroids may temporarily improve signs/symptoms of crusted scabies, but the infestation will eventually worsen because of the immunosuppressive effects of these agents. Patients on systemic immune-suppression therapy for their psoriasis can also be prone to develop crusted scabies.
Psoriasis: Manifestations, Management, and Mimics
Some cutaneous malignancies are very slow growing and may display red plaques and scales similar to those seen in psoriasis (shown), and many of these tumors have an inflammatory component that may respond to topical corticosteroid therapy. A clue to differentiating these disorders is that cutaneous malignancies most often present as a solitary lesion, whereas having a single psoriatic plaque is possible but atypical. The presence of gluteal pinkening, nail pits, or a refractory dandruff supports the diagnosis of psoriasis. The following dermatologic maxims may also apply:
- If it is not responding to what should be effective treatment, biopsy it.
- If the biopsy results conflict with the patient's history and physical findings, biopsy again.
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