Pustular Psoriasis: Symptoms, Causes, Diagnosis & Treatment

Introduction

Pustular psoriasis is a rare, immune-mediated systemic skin disease characterized by yellowish pustules on an erythematous background with various clinical manifestations and the prevalence of foci (1). Pustular psoriasis is considered a variant of vulgar psoriasis. Pustules can be common or localized and are characterized by a sterile predominantly neutrophilic infiltrate. Unlike chronic plaque psoriasis (the most common variant of psoriasis Vulgaris), lesions in pustular psoriasis are often painful on palpation (2). Pustular psoriasis can be classified based on the clinical picture and location of the pustules.

Subtypes of pustular psoriasis include:

• Generalized;
  • Tsumbusch subtype: Diffuse generalized pustular rash with concomitant systemic symptoms (fever, arthralgia, etc.);
  • Ring-shaped subtype: Annular lesions with pustules along the edge of the lesions.
  • Exanthematous subtype: Acute pustular rashes without systemic symptoms that go away after a few days.
  • Impetigo herpetiformis: Pustular psoriasis that occurs during pregnancy.
• Localized:
  • Acrodermatitis persistent Allopo: Pustules affecting the fingers of the hands, feet, and nail beds.
  • Palmoplantar psoriasis: Pustules affecting the palms and soles

Aetiology

Pustular psoriasis occurs when there is a genetic predisposition and can be triggered by certain risk factors leading to psoriasis-like changes and a pronounced accumulation of neutrophils in the epidermis (3). Patients with pustular psoriasis have an increased incidence of the HLA-B27 allele compared to the general population. Most cases of pustular psoriasis are idiopathic, however, risk factors that may play a role in the etiology of pustular psoriasis include (4, 5):

• Sudden withdrawal of systemic steroids
• Skin infections (Staphylococcus aureus)
• Electrolyte imbalance; hypocalcemia (e.g. Zumbusch subtype)
• Drugs (lithium, iodine, penicillin, interferon-alpha, etc.)
• Pregnancy (e.g. impetigo herpetiformis)
• Phototherapy
• Vaccination (BCG and H1N1)

Epidemiology

Pustular psoriasis is a rare disease. It affects both children and adults; the bimodal age distribution is characteristic. In the adult age group, this disease manifests itself between the ages of 40 and 50 years, whereas in the children’s age group it tends to manifest itself in infancy.

Residents of Asian countries tend to have this disease more often than residents of Caucasus (6). Women and men get sick equally often. Pustular psoriasis accounts for approximately 1% of all clinical cases of psoriasis Vulgaris (5).

Pathophysiology

The exact pathogenesis of pustular psoriasis is not fully understood. However, based on the study of the expression of certain cytokines and reactions to specific drugs, several mechanisms have been proposed.

The combination of genetic predisposition and exposure to certain triggering factors (such as the withdrawal of systemic corticosteroids) leads to increased regulation of specific cytokines and the accumulation of neutrophils in the epidermis (5).

Additionally, the skin’s dendritic cells secrete elastase, which may play a role in pustule formation (7). Both pustular psoriasis and chronic plaque psoriasis exhibit overexpression of IL-1, IL-17, IL-23, IL-36, TNF-alpha, and IFN-gamma. However, the expression of IL-1 and IL-36 is more pronounced in pustular psriasis.

Studies have also found a deficiency of the IL-36 receptor antagonist in patients with pustular psoriasis, and patients with pustular psoriasis have also been successfully treated with a new monoclonal antibody against the IL-36 receptor (8).

Therefore, IL-36 probably plays a crucial role in the pathogenesis of pustular psriasis.

Histopathology

Many of the histopathological features of pustular psoriasis are similar to that of psoriasis Vulgaris, including the preservation of nuclei in the stratum corneum (parakeratosis), thickening of the stratum corneum (hyperkeratosis), elongation of the dermal papillae, thinning of the granular layer and epidermisal zones (5).

In addition to the classic histological signs of vulgar psoriasis, there is also a pronounced neutrophilic infiltrate in the papillary dermis and epidermis, causing basal keratinocytes to press into the papillary layer of the dermis, destroying the desmosomal compounds of keratinocytes (spongiosis) and leading to the development of superficial microabscesses (9).

Neutrophilic infiltration of the epidermis is more pronounced in pustular psoriasis than in other variants of vulgar psoriasis.

Clinic

Pustular psoriasis manifests itself in the form of numerous focal or merging superficial yellowish pustules against the background of erythema.

Pustular psriasis can be diffuse or localized. A complete skin examination should be performed, including a thorough evaluation of the mucous membranes and nails for other signs of psoriasis and to rule out other causes of pustulosis.

Pustular psriasis begins with red papules or plaques, which quickly turn into yellowish, superficial pustules against the background of erythema.

The generalized subtype of Tsumbush is usually manifested by systemic symptoms such as fever, joint pain, headaches, and leukocytosis.

The exanthematous subtype, on the contrary, is represented by acute pustular rashes without systemic symptoms. The ring-shaped subtype is more common in children as ring-shaped lesions with pustules along the edge of the main rashes (10).

Persistent allopo acrodermatitis affects the fingers of the hands, feet, and nail beds. Palmoplantar psoriasis, which can be thought of as part of Sapho syndrome, affects the palms and soles.

Survey

Patients with suspected pustular psriasis require a thorough examination, as the Tsumbush subtype can be life-threatening.

Laboratory tests should include a complete blood count (CBC) to assess leukocytosis, an electrolyte panel to assess hypocalcemia, and a liver panel to assess transaminitis.

A pregnancy test should be administered to all women of childbearing age. A punch biopsy may be performed in doubtful cases.

A culture study of weeping lesions may be useful to rule out primary or secondary infections.

Treatment / Patient Management

The first step in treating pustular psoriasis is to identify the triggers of the disease, such as the underlying infectious process.

Generalized pustular psoriasis (e.g., the Tsumbusch subtype) may require hospitalization. Systemic symptoms, including fever and joint pain, require treatment with antipyretic and anti-inflammatory drugs.

Specific drugs for the treatment of this disease, including systemic retinoids (acitretin, isotretinoin), methotrexate, cyclosporine, and infliximab, are considered first-line drugs in adult patients. In children, acitretin, cyclosporine, methotrexate, and etanercept are preferred (11).

Second-line drugs include systemic therapy for diffuse lesions (e.g., etanercept and adalimumab) or topical treatment for localized lesions (e.g., corticosteroids, calcipotriene, and tacrolimus). All of these drugs can be used as monotherapy or in combination with first-line drugs (12).

Phototherapy is another treatment option (13). Early delivery is recommended for pregnant patients with herpetiform impetigo.

Recent research suggests the successful use of IL-1 receptor antagonists (e.g., anakinra) and IL-36 receptor antagonists in the treatment of pustular psriasis (8).

Tocilizumab, a monoclonal antibody against the IL-6 receptor, has also been shown to be effective in some therapy-resistant cases of pustular psriasis (14).

Differential diagnostics

• Acute generalized exanthematous pustulosis
• Reactions to medication
• Vulgar pemphigus
• Pemphigus leaf-shaped
• Impetigo
• Dermatitis herpetiformis
• Microbial eczema
• Erythroderma
• The acute cutaneous form of lupus erythematosus
• Dyshidrotic eczema
• A common form of herpes simplex virus infection

Forecast

Pustular psoriasis is a chronic disease characterized by a recurrent course. Treatment is aimed at reducing the duration of relapse, preventing complications, and prolonging the relapse-free period.

Compared to other subtypes, the Tsumbusch subtype of pustular psoriasis has a higher risk of mortality due to systemic lesions, especially when combined with comorbidities such as sociopathology, kidney failure, or liver failure. Localized subtypes of pustular psriasis have a much lower risk of mortality.

Complications

• Hypocalcemia
• Septicemia, especially with a generalized form
• Hyperthermia
• Liver damage
• Acute renal failure
• Depletion

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Informing and educating patients

Patients with psoriasis should be aware of the advisability of avoiding abrupt withdrawal of steroids, which can provoke episodes of pustular psoriasis. Sluggish lesions should be treated with proper care for the elements of the rash to avoid complications and secondary infections.

Improving the performance of medical personnel

Treatment of pustular psriasis requires an interdisciplinary approach, including primary care staff, dermatologists, and infectious disease specialists. A detailed history and complete physical examination are crucial in diagnosing cases of pstular psoriasis.

A dermatologist can assist in the initial diagnostic examination and assess the presence of complications. Depending on the area of the lesion, hospitalization may be required (for example, the Tsumbush subtype). In doubtful cases, a biopsy can be performed, since differential diagnosis with other pustular lesions is quite extensive. Treatment is aimed at preventing relapses and reducing their duration.

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