Overview

Psoriasis is a common long-term skin issue with no cure. It's thought to be a problem with the immune system, making skin cells grow faster than the normal rate. A significant part is played by both genetic and environmental variables.

There are local treatments or photo therapies, and full body treatments like regular therapy and biotherapy available. Most of the time, these are good enough to manage this skin issue.

Introduction 

Psoriasis is a chronic inflammatory skin disease characterised by the formation of erythematous, sharply defined scaly plaques. It is a skin disorder that commonly affects the elbow, scalp, trunk, and knees. 

A normal individual would take up to 3-4 weeks for cell maturation, migration to the skin surface, dividing, and sloughing; however, in psoriasis, the same events occur only 3-7 days.

Triggers for psoriasis include skin injuries, medications (e.g. lithium, quinidine, antimalarial drugs), infections, and stress. Other factors for this illness include allergies, the weather, and food.

Pustular forms can develop in small areas of the sole and palm or cover extensive regions. The generalised pustular, palmoplantar, and acrodermatitis continua of Hallopeau are the most precisely defined subtypes.

The pustular type of psoriasis may present as the generalised type and in the form of recurrent illness that is systemic, or as the palmoplantar type and in the form of a locally focused disease mostly affecting the sole and palm, or in acrodermatitis in the nail beds or its digits.¹

Pustular psoriasis

Pustular psoriasis is an uncommon type that is characterised by pus-filled lesions.

Pustular psoriasis refers to a diverse collection of skin inflammatory illnesses characterised by the presence of aseptic pustules.¹ They have been linked to mutations in any of three skin immune system genes, known as IL36RN, CARD14, and AP1S3.³

There are four subtypes of pustular psoriasis: 

1. Generalised pustular psoriasis (GPP), von Zumbusch
2. Annular or circinate pustular psoriasis
3. Exanthematic pustular psoriasis
4. Localised pustular psoriasis, which includes palmoplantar pustular psoriasis (PPPP) and acrodermatitis continua of Hallopeau (ACH) variants⁹

Generalised pustular psoriasis (GPP)

Generalised pustular psoriasis (von Zumbusch) is an uncommon and acute eruption characterised by erythematous and oedematous plaques with many pustules, which may or may not be connected with the plaque form.²

This condition is more common in women and can affect people of all ages.

In all pustular psoriasis variations, mutations in the IL-36RN gene are associated with an earlier onset. Von Zumbusch GPP is the most severe and potentially life-threatening presentation.

Types 

• Annular GPP (Lapie're-Millian): annular lesions with peripheral pustules that develop from 7 days to 3 months. Symptoms are often minor
• Chronic acral GPP causes lesions that start in acral locations and progress to a pustular flare
• Mixed GPP’’ has features associated with more than one subtype

Clinical manifestation

• Erythema and oedema in significant skin regions. The skin is tender and painful. Within hours, sterile non-follicular pustules emerge and expand to form lakes of pus
• Geographic tongue and lip desquamation/exulceration. Subungual pustules may be present²
• As the illness worsens, pustules dry out and scarlatiniform desquamation occurs, resulting in a smooth, shiny surface. This normally lasts for several weeks
• Systemic symptoms may include fatigue, malaise, anorexia, nausea, tremors, fever, conjunctivitis, or uveitis

Diagnostic criteria

Modified psoriasis clinical disease assessments, such as the Generalised Pustular Psoriasis Physician Global Assessment (GPPGA) and Generalised Pustular Psoriasis Area and Severity Index (GPPASI), have been designed to specifically assess GPP.⁴

The 2018 Japanese guidelines specified the following diagnostic parameters:

• Symptoms may include fever and fatigue
• flushing
• multiple sterile pustules
• spongiform pustules of Kogoj
• recurrence of previous findings

Triggering factors

Upper respiratory tract infections, sunburns, irritation from coal tar and anthralin, stress, pregnancy, or an idiopathic trigger.

Medications used include lithium, salicylate, tar, chloroquine, beta-blockers, indomethacin, and systemic corticosteroids.²

Differential diagnosis 

Other pustular dermatoses, such as Sneddon-Wilkinson subcorneal pustulosis, IgA pemphigus, amicrobial pustulosis of the folds, and, most importantly, AGEP, are used to make the clinical differential diagnosis.⁴

Treatment 

The first retinoid to be studied was Etretinate, which was followed by Acitretin.

The suggested dose is 0.75 to 1 mg/kg/day, and patients typically respond within 7 to 10 days.

Methotrexate: 15-25mg each week.

Spesolimab was recently licensed in the United States and Japan for the treatment of GPP flares in adult patients.

The National Psoriasis Foundation Pustular Psoriasis Treatment Guidelines (2012) designated infliximab as the first-line treatment, with etanercept and adalimumab as second-line treatments.

Psoriasis treatment options include topical, phototherapy, systemic non-biological, and systemic biological. Topical therapies are not advised for GPP as they flare-up.⁴

Complications

This includes bacterial superinfection, metabolic, haemodynamic, and thermoregulatory problems, renal, hepatic, and cardiac failure, acute respiratory failure, neutrophilic cholangitis, pancreatitis, aseptic and hypovolemic shock, and even death.

Palmoplantar pustular psoriasis

Palmoplantar pustulosis (PPP) is characterised by the chronic formation of sterile pustules on the palms and soles.

PPP was formerly known as 'pustular psoriasis of the extremities.⁶

The condition primarily affects women in their sixth and seventh decades of life.

Skin lesions are typically found on the palms and soles of the feet, but they can migrate to the lateral areas of the hands and feet. The main lesions are sterile pustules with an erythematous and desquamative background. The lesions are typically painful.¹⁰ Nail lesions (similar to those seen in psoriasis vulgaris) are also present. The most prevalent features include nail pitting, onycholysis, subungual pustules, and nail dystrophy.⁵

The genetic background of palmoplantar pustulosis (PPP) is complex and distinct from those of other kinds of psoriasis.⁶ IL-17 activates and infiltrates neutrophils, contributing to the major immune response.^5,6

Based on their clinical experience, Ammoury et al. proposed the PPP triad: pustulosis, smoking, and jewel intolerance.¹⁰

Types

1. One subtype is chronic and treatment-resistant
2. The second subtype is characterised by flare-ups of skin lesions and prolonged remissions

Etiopathogenesis

According to pathophysiological concepts, infections, such as acute tonsillitis, can worsen PPP.

Symptoms

Occasionally, scaly erythemas form on the scalp. In rare situations, erythematous lesions with scaling may appear on the trunk and cause joint discomfort after infections, including tonsillitis, dental infections, and sinusitis. Patients with extra palmoplantar lesions exhibit significant cutaneous and musculoskeletal symptoms.⁵

The most prevalent finding in the nail is onycholysis, which is followed by pitting and destruction.

Other nail modifications include scaling, subungual hyperkeratosis, pustulation, indention, transverse and longitudinal ridging, curvature abnormalities, discolouration, splinter haemorrhage, and nail thickening. 

Triggering factors

• Smoking
• Tonsillitis
• Dental infections
• Dental metal allergy
• Triggering drugs - anti-tumour necrosis factor (TNF) agents

Differential diagnosis

Folliculitis should be differentiated from the primary symptoms, especially when it manifests as pustular lesions on the lower limbs.⁶

PPP can be classified into the 3 phases

• Vesicle,
• Pustulovesicle,
• pustule phases, Topical Treatment 

Treatment

PPP is a chronic illness that is highly resistant to treatment.

Topically applied glucocorticosteroids, vitamin D derivatives, retinoids, keratolytic agents, and emollients are utilised. Systemic treatments include acitretin, PUVA, Re-PUVA, methotrexate, ciclosporin, excimer laser, and biological therapy, with varying success.^5,6 Topically applied glucocorticoids, vitamin D derivatives, retinoids, keratolytic agents, and emollients are commonly utilised to treat skin lesions after 8 weeks of maxacalcitol therapy.

PPP is treated using phototherapy, which includes PUVA, NB-UVB, excimer light therapy, and photodynamic therapy (PDT). 

NB-UVB phototherapy using a flat-type fluorescent lamp produced moderate to significant improvement.⁶

Three cycles of Grenz ray therapy at a dose of 5 Gy per treatment resulted in significant improvement, which was sustained for three months. 

Acitretin is the most often utilised systemic therapy in PPP.

Secukinumab and brodalumab, two IL-17 inhibitors, have been studied for the treatment of PPP.

In conclusion, phototherapy is considered a well-established treatment with a high response rate, but relapses are common.

Complications

Mechanical stimulation, such as shoes and the topical application of disposable chemical pocket warmers to the soles, can either cause or worsen PPP lesions.

Extra-palmoplantar lesions can also be caused by wearing a ring on the fingers or by the rubbing of the elastic of undergarments against the abdomen.⁶

Acrodermatitis continua of hallopeau

Acrodermatitis continua of Hallopeau (ACH) is an uncommon, sterile pustular eruption affecting one or more fingers. The condition is characterised by sensitive pustules with underlying erythema on the tip of a digit, which occurs more frequently on the finger than the toe.

This condition is also known as pustular acrodermatitis, acrodermatitis continua suppurativa, dermatitis perstans, acropustulosis, acrodermatitis perstans, and dermatitis repens.^7,8

Current data suggests that ACH is linked to a number of genetic alterations in the genes IL36RN, CARD14, and AP1S3.⁷ ACH is a localised form of pustular psoriasis, which is more frequent in middle-aged women.

The eruption usually happens after a local trauma or infection.

ACH becomes chronic over time and can progress proximally to the dorsal portion of the hand or foot. 

Symptoms

One digit's tip may start off erythematous and develop painful pustules, which may then spread beneath the nail bed and matrix and cause onychodystrophy.

In the acute phase, the pustules burst and clump together to create "a lake of pus that carries the nail away." ⁷

The ensuing anonychia leaves behind a smooth, glossy, and erythematous distal digit where pustules frequently start to form.

Hyperkeratotic fingers with psoriasiform scaling and persistent pustulation may emerge as the condition worsens; Joint discomfort and arthritis may develop.⁷

ACH may develop into GPP, especially the potentially fatal von Zumbusch variety. 

Differential diagnosis

Pemphigus vulgaris can mimic ACH by exhibiting digit erosion and inflammation.

PPP is the most crucial condition to contrast and compare with ACH.⁸

Treatment

Consists of cyclosporine, methotrexate, topical and systemic retinoids, topical and oral corticosteroids, topical vitamin D analogues, topical fluorouracil, topical calcineurin inhibitors, and phototherapy or photochemotherapy.⁷

The treatment of ACH has been significantly transformed in recent years by the advent of biologics, a novel type of medication.

The usage of IL-17 inhibitors like secukinumab, IL-12/23 inhibitors like ustekinumab, IL-1 inhibitors like anakinra, and anti-TNF medications like infliximab, adalimumab, and etanercept is also advised.⁷

Complications

Osteolysis of the distal phalanges due to osteitis and onychodystrophy, which can cause anonychia in addition to symptoms.⁸

Conclusion

Dermatologists often face clinical difficulties when treating pustular psoriasis, an uncommon kind of psoriasis.

New medications for pustular psoriasis may be able to treat the condition more quickly and effectively while having fewer side effects than current treatments.

There aren't many evidence-based treatment choices, which limits treatment possibilities.

Both PPP and GPP are less prevalent, which can make diagnosis and treatment choices challenging due to a lack of available treatments.

Targeted therapy clinical studies conducted recently have produced promising outcomes for the treatment of crippling skin conditions.

Thus, in order to optimise the patient's knowledge, medical education initiatives are necessary.