Clinical Presentation and Subtypes of Psoriasis

Introduction

Psoriasis can involve any area of the skin. The most common areas are those that are prone to significant trauma from rubbing or scratching. These areas include the elbows, knees and scalp. However, psoriasis can present anywhere and it is not unusual to see it limited to the genitals or nails. Likewise, there are multiple clinical subtypes of psoriasis that may appear clinically distinct yet share a common genetics and pathophysiology. Importantly, it is critical to remember that these clinical classifications are not exclusive. Patients can have multiple areas on their body affected by chronic plaque psoriasis but also have pustules on their palms and soles.

The predominant subtype of psoriasis is not always stable over time. For example, patients may have their initial presentation as a guttate flare, then progress to more extensive chronic plaques in the future. Additionally, environmental factors may play a role in the clinical presentation of disease. Exposure to and withdrawal of acute high doses of systemic corticosteroids may turn a patient with limited plaques into someone who has a severe pustular flare.

Plaque Psoriasis

Plaque psoriasis, sometimes referred to as chronic plaque psoriasis, is the most common presentation of this disease. It occurs in over 80% of patients with psoriasis. As shown in Figure 4-1, plaque psoriasis is the classic presentation of psoriasis featuring the cardinal clinical features of the disease, including redness, scaling and induration, thickness in lesions that can be felt above the level of the surrounding skin. These plaques are usually well demarcated with very visible borders. While the general features of redness, scale and induration are common for all plaques of psoriasis, they may vary in their extent. A lesion may be deeply erythematous but only have limited scale. Likewise, lesions may be very relatively thick or thin and have various shades of erythema. As mentioned, these have a propensity to develop in areas that are frequently traumatized. This response to trauma is referred to as the Koebner phenomenon (Figure 4-2). Psoriatic plaques often develop in places where the skin has been damaged. Physiologically, the Koebner phenomenon is probably related to the initial signal from keratinocytes initiating the inflammatory process.

Traditional teaching suggests that psoriatic plaques are not particularly symptomatic. However, some studies suggest that patients with psoriasis suffer from a number of symptoms from their plaques. The most common of these are itching and pain. The itch in psoriatic plaques can range from an occasional nuisance-type itch to severe pruritus. Scratching of these lesions can induce Koebnerization and worsening of individual lesions. Patients also complain of other symptoms related to their plaques, including pain (potentially severe), skin cracking and bleeding. Bleeding, in particular, is notable due to the increase in the vasculature in the upper dermis of psoriasis lesions. Removing a small amount of scale with resultant pinpoint bleeding is a well-known element of psoriasis called Auspitz Sign.

The clinical course of chronic plaque psoriasis is variable. As the name suggests, most patients will have the disease chronically. However, there is generally a waxing and waning course with periods of relatively limited disease alternating with more extensive involvement. Patients should be aware that it is rare to have complete remission without treatment.

Enlarge 

Enlarge 

Guttate Psoriasis

Guttate psoriasis is a condition where there are a multitude of small plaques distributed diffusely over the trunk and extremities (Figure 4-3). The clinical appearance of guttate psoriasis can occur in two different scenarios. The first is a slow development of small psoriasis lesions that may become confluent. These lesions can generally be considered simply a variation of chronic plaque psoriasis and can be referred to as small plaque psoriasis. The most important consideration in these patients who have chronic small plaques of psoriasis is the difficulty in applying topical medication to many small areas, even if the total body surface area (BSA) covered is limited.

Guttate syndrome is distinct from small plaque psoriasis in that it occurs suddenly and explosively. Typically, a young patient who has not had active psoriasis in the past will acutely develop hundreds of small psoriasis lesions in relation to an infection, often streptococcal pharyngitis. Importantly, while infection is often associated with guttate syndrome, a treatable source is not always identified. This form of psoriasis often will regress after time or initial treatment but in many cases, patients who initially present with guttate syndrome will go on to develop plaque psoriasis later in life.

Enlarge 

Palmar-Plantar Psoriasis

Less common as the primary presentation of psoriasis but one that can accompany other forms is palmar-plantar disease (Figure 4-4 and Figure 4-5). While this condition can be limited in body surface area (BSA) of coverage, it can be devastating in its impact on patients. Palmar-plantar psoriasis can present as well-demarcated lesions appearing on the palms, soles or some combination of both. Usually not having a very noticeable level of added thickness to the already thick skin of these areas, these lesions often are accompanied by pustules, even if other areas of the affected skin are not pustular. These pustules can often be confused with palmar-plantar pustulosis, a distinct but related entity that most investigators do not believe is a variant of psoriasis. One element that is frequently overlooked is that patients who have allergic or irritant contact dermatitis can often have involvement in these areas related to the Koebner phenomena (Figure 4-6). It is sometimes necessary to perform patch testing on patients who do not respond.

What is critical of palmar-plantar disease is the impact it can have on a patient’s life well beyond what would be predicted by the surface area involved. Due to the thicker epidermis on the palms and soles, there is less flexibility in the skin and these lesions can lead to skin cracking that can be extremely painful. Constant pressure on plantar lesions during walking can also lead to significant discomfort. Moreover, the use of hands and feet for normal activities of daily living can be impeded with psoriatic plaques in these areas. Finally, it is critical not to underestimate the social and economic issues associated with psoriasis on the hands and feet, especially on the palms. Working with the hands and jobs that require significant mobility may be much more difficult with this form of psoriasis. Additionally, simple accepted social and economic behaviors, like shaking hands, can become a major chore and a source of alienation for patients who suffer from palmar-plantar disease. While palmar-plantar disease may be of limited scope in area involved, it can make a tremendous impact on patient lives.

Enlarge 

Enlarge 

Enlarge 

Pustular Psoriasis

As with many other clinical presentations of psoriasis, pustular psoriasis comes in a variety of forms and extent. The two major forms are limited pustular psoriasis and a generalized eruption, sometimes referred to as pustular psoriasis of von Zumbusch (Figure 4-7 and Figure 4-8). The localized disease involves plaques of psoriasis that have small, white pustules that are sometimes painful. These are treated as other localized lesions and are often responsive to topical treatment.

Disseminated pustular psoriasis can be chronic or explosive, particularly in cases that follow acute withdrawal of systemic corticosteroids or sometimes cyclosporine. Patients will have diffuse erythematous patches and plaques with many sterile pustules. Most often, this will occur in patients with a history of psoriasis but sometimes it is an initial presentation. Physicians will often be concerned with infection in these patients, particularly when it is associated with other constitutional symptoms. Patients can have high fever, increased white blood cell count and even hypotension associated with disseminated acute pustular psoriasis. While sometimes topical treatments and rest can result in the resolution of these lesions, most clinicians feel that an acute presentation will almost always require effective systemic treatment with highly effective, acutely acting medication, such as cyclosporine or an anti-TNF agent.

Enlarge 

Enlarge 

Erythrodermic Psoriasis

Erythrodermic psoriasis is an uncommon presentation but can be tremendously debilitating. Erythroderma is, by general consensus, a cutaneous condition that covers over 80% of the body surface area (BSA). In fact, erythrodermic psoriasis is somewhat distinct from plaque psoriasis covering wide areas. In general, erythroderma is characterized by plaques that are of a deeper erythema with finer scale than plaque psoriasis (Figure 4-9). Erythroderma is considered a clinical pathway common to a number of inflammatory conditions of the skin, most commonly psoriasis in adults, but also atopic dermatitis, severe seborrheic dermatitis, cutaneous T cell lymphoma and pityriasis rubra pilaris. When erythroderma is an initial presentation of disease, it is of vital importance to try to differentiate it from other skin conditions, most importantly cutaneous T cell lymphoma, by looking for atypical lymphocytes on skin biopsy.

As with acute disseminated pustular psoriasis, erythrodermic psoriasis is considered to be a severe medical condition. Along with fever, patients often have significant chills and severe edema, particularly in their legs. Laboratory test abnormalities will include a high white blood cell count and even metabolic and electrolyte abnormalities. Patients can have evidence of cardiac failure due to significant blood flow being diverted to the skin. In all, erythrodermic psoriasis will usually require acute, systemic treatment that will need to be maintained to prevent recurrence.

Enlarge 

Special Locations of Psoriasis

A significant aspect of psoriasis is the location of the disease on the body. There are a number of locations that require special consideration. Inverse psoriasis, including the skin folds and face, involvement of the genitalia and the nails require special mention as they have aspects that differentiate them from other body surfaces that can be affected by psoriasis.

Inverse Psoriasis

Inverse psoriasis is often considered to be a separate type of psoriasis, but it most often occurs in patients who suffer from plaque psoriasis. It occurs in areas where the skin is thinner and there is generally more moisture caused by sweating and physical occlusion. Typically, inverse psoriasis is thought of as involving the skin folds, primarily in the axillae and in the groin (Figure 4-10). The face is often considered distinct from inverse psoriasis but the concerns with the face are so similar to the other areas that we will consider it here.

The clinical appearance of inverse and facial psoriasis is often somewhat distinct from plaque psoriasis due to differences in lesional borders and scale. The borders are often less distinct than those typically seen in plaque psoriasis and there even may be small satellite lesions associated with local yeast superinfection. The most prominent yeast in the groin and axilla is candida albicans, while on the face and the chest area it is often malassezia furfur. Scale is typically milder, finer and has a waxy appearance related to the increased moisture in these areas.

There are special considerations for treatment in these areas due to the differences in the local skin and the possibility of local yeast superinfection. The relatively thin epidermis in these areas requires use of milder topical corticosteroids or even topical calcineurin inhibitors that are not likely to cause atrophy. Additionally, keeping the area dry and yeast-free can be of benefit and the use of an antifungal powder or cream can be of some benefit.

Enlarge 

Genital Psoriasis

Psoriasis of the genital areas on both men and women is often not considered by patients or physicians. Presentation of small patches or plaques with mild scale should alert the practitioner to the possibility of psoriasis when evaluating erythematous eruptions of the genitals. The differential diagnosis of psoriasis in the genitalia would include conditions such as lichen sclerosus et atrophicus, contact dermatitis or, much less likely, localized fungal infections. The considerations concerning inverse psoriasis, including skin thinning, need to be considered in treatment. Importantly, increases in local squamous cell carcinoma preclude the use of phototherapy for these areas.

Nail Psoriasis

Psoriasis involving the nails is clinically apparent in about 40% of patients without PsA and in approximately 80% of patients with PsA. Recent MRI findings suggest that the nails may be an extension of the peripheral joint spaces, implying that inflammation in the joints may spread locally to the nail matrix. This theory has recently been called into question but remains an intriguing idea as to why nail disease most often correlates with joint disease.

Clinically, there are two aspects of nail psoriasis, involvement of the nail matrix causing changes in the nail plate, and involvement in the nail bed with visible changes under the nail plate. Matrix disease most commonly presents as pits in the nail or other deformities in the plate (Figure 4-11). Psoriasis under the nail can result in discoloration under the nail, called “oil drop spots,” or thickening of the skin of the nail bed causing sub-ungual hyperkeratosis and detachment of the nail called onycholysis. None of these changes is specific for nail psoriasis. However, the constellation of clinical signs will often strongly suggest psoriasis. Nail disease, like palmar-plantar disease, can be debilitating from symptoms, mainly pain, or from social impact.

Nail disease presents among the most difficult aspects of psoriasis to treat. Since the nail matrix and the nail bed are not easily accessible for topical medications, nail disease often requires systemic medications. There have been occasional reports of topicals or even laser therapy having some impact on nail disease, but these are relatively inconclusive and of little clinical benefit for most patients. Even most effective systemic medications like cyclosporine or anti-TNF agents have less impact on nails than on body plaques. For patients whose primary disease is in the nails, there needs to be a calculation whether the relative benefits of treating primary nail disease outweigh the risks.

Enlarge 

Laboratory Evaluation of Psoriasis: Histopathology

Diagnosis of psoriasis is almost purely clinical. There are no specific diagnostic tests for psoriasis. In general, for patients who are otherwise healthy, almost all diagnostic tests are normal. When psoriasis is very severe, particularly in patients with pustular or erythrodermic psoriasis, the white blood cell count may be elevated. Markers of systemic inflammation such as the ESR and CRP are typically not elevated when psoriasis is not accompanied by PsA. Thus, an evaluation of psoriasis with diagnostic tests is almost never indicated.

The one diagnostic test that can be of some benefit is skin biopsy. It is, however, critically important to remember that the diagnosis of psoriasis is rarely made by skin biopsy. Additionally, the biopsy is not always perfectly in line with the clinical skin disease. Proper discretion needs to be used when choosing to do a skin biopsy for a diagnosis of psoriasis, as it is often not helpful. Given the subtle nature of reading the biopsy, it is imperative that the biopsy be read by a pathologist trained in dermatopathology.

There are a number of distinguishing features that can lead a dermatopathologist toward a diagnosis of psoriasis (Figure 4-12 and Figure 4-13). These changes are both in the epidermis and dermis of the skin. In the outermost layer of the epidermis, the stratum corneum, the normal basket weave appearance is replaced by thickened layers of scale in which the cells retain their nuclei, which are normally lost in maturation. The appearance of this hyperkeratosis and parakeratosis is relatively specific for psoriasis. In the lower areas of the epidermis there are inflammatory cells including lymphocytes, particularly CD8+ T cells and groups of neutrophils, sometimes collecting in microscopic collections called Poutrier’s microabscesses. There is usually only very limited spongiosis between the keratinocytes that can help distinguish psoriasis from spongiotic dermatitis. Finally, there is thickening (acanthosis) of the epidermis with enlargement of the rete ridges and, conversely, thinning of the suprapapillary plates.

In the dermis, there are a number of elements that are suggestive of psoriasis. The superficial blood vessels in the dermal papillae tend to be thickened and more numerous than in unaffected skin. Most prominent in the dermis is the infiltrate of lymphocytes. These lymphocytes are primarily CD4+ and tend to be arranged perivascularly. There are usually some neutrophils and monocytes and dendritic cells in the infiltrate, but it is the lymphocytes that are most evident.

Enlarge 

Enlarge