Pustular Psoriasis: What is its uniqueness?

Pustular psoriasis is a term referring to a rare form of psoriasis that is non-contagious skin condition. Its prevalence is estimated at 2 cases per 1 million people. Pustular psoriasis is characterised by a sudden and widespread outbreak of superficial sterile pustules. They are non-infectious, but inflammatory. These pustules are the size of a pinhead and can merge with each other.

The lesions caused by this disease can be localised in a specific area or spread across all parts of the body. They are accompanied by pain, a burning sensation or itching in some patients. It happens that the same individual may suffer from both pustular psoriasis and plaque psoriasis. In this case, the plaques of the rash can be scaly and erythematous. There are a few rare cases where the pustules reach the extremities of the fingers and toes. Generally speaking, pustular psoriasis can affect any individual of any age.

Pustular psoriasis presents itself in two forms:

• Palmoplantar Pustulosis (PPP): This term is used when the lesions of the disease are concentrated on the hands or the soles of the feet.

• Generalised Pustular Psoriasis (GPP): this term is used when the lesions of the disease spread over the entire body.

Pustular psoriasis may be accompanied by the following systemic symptoms:

• Chills;

• Fever or headaches;

• A general feeling of discomfort;

• Joint pains;

• Sensations of burning;

• Affliction of the lips (psoriatic cheilitis).

The abrupt discontinuation of corticosteroid-based treatments in patients suffering from plaque psoriasis is often the first cause identified as a trigger for pustular psoriasis. Generally, the products used for these treatments are gradually discontinued when they are prescribed for more than 5 days.

Pustular psoriasis is not caused by poor skin hygiene or bacteria. It originates from a genetic factor associated with an overactive immune system.

One of the suspected causes of the frequent onset of this pathology is the administration of certain medications such as aspirin derivatives and lithium or the initiation of certain drugs like ustekinumab.Smoking and stress are not triggering factors for this disease, but they can exacerbate its flare-ups.

Complications related to this disease can occur for a multitude of reasons: a secondary bacterial infection, hypoalbuminemia, hypocalcemia, renal tubular necrosis, or malnutrition. Furthermore, untreated patients have an increased risk of cardiorespiratory failure. Mortality data from studies on patients with GPP are limited, but rates of 3% and 7% have been reported.

Immediate intervention is necessary in the case of palmoplantar pustulosis due to the pain it can cause. The treatment is based on topical corticosteroids such as ointments, creams, or lotions. If this option proves ineffective, doctors turn to phototherapy or drug treatments using Methotrexate, Ciclosporin, or Acitretin.

For cases of pustular psoriasis on the nails, the treatment involves injections of corticosteroids under the nails. This treatment inflicts intense pain on patients, which necessitates doctors to suggest phototherapy or the use of urea-based nail varnish as an alternative.

Complications are not uncommon with generalised pustular psoriasis. It is advised to consult a doctor as soon as symptoms appear. Treatment may include the prescription of retinoid-derived medications or phototherapy sessions.

ZELICKSON B. D. & al. Generalized pustular psoriasis. A review of 63 cases. Archives of Dermatology (1991).

CHOON S. E. & al. Clinical profile, morbidity, and outcome of adult-onset generalized pustular psoriasis: analysis of 102 cases seen in a tertiary hospital in Johor, Malaysia. International Journal of Dermatology (2014).

GOODERHAM M. J. & al. An update on generalized pustular psoriasis. EXPERT REVIEW OF CLINICAL IMMUNOLOGY (2019).