Annular and circinate variant of pustular psoriasis in a young woman

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A 21-year-old woman presented with gradually progressive, scaly lesions involving the extremities, trunk, and scalp since childhood. The lesions had a waxing and waning course, were mildly pruritic, and tended to worsen during winter with complete remission in the summer. She had no associated systemic or mucocutaneous symptoms and reported minimal improvement despite treatment with oral steroids and steroid-sparing agents. Cutaneous examination revealed multiple discrete annular plaques with peripheral pustules, ranging from skin-coloured to erythematous, forming arcuate and circinate patterns predominantly over the upper limbs. The plaques showed peripheral collarette scaling and erythema with central hyperpigmentation [Figures 1a and b]. Systemic and mucosal examination was unremarkable, and routine blood tests, including antinuclear antibodies, were within normal limits. Potassium hydroxide preparation was negative for fungal elements. Histopathology from lesional skin revealed subcorneal neutrophilic microabscesses, hyperkeratosis, parakeratosis, mild to moderate acanthosis, moderate to dense neutrophilic exocytosis, and focal spongiform changes. There was also a perivascular infiltrate of lymphocytes, histiocytes, and neutrophils in the superficial dermis [Figures 2a and b]. Direct immunofluorescence from perilesional skin was negative for IgA, IgG, and C3. Whole-exome sequencing did not identify any pathogenic mutations. Based on clinical presentation and histological findings, a diagnosis of the annular and circinate variant of pustular psoriasis was made, an uncommon form that typically presents in childhood. The patient was initiated on oral cyclosporine (3 mg/kg/day) with marked clinical improvement and sequentially switched to tablet methotrexate (10 mg/week). Her lesions have since resolved, and she remains stable on regular follow-up [Figures 3].

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Figure 1:

Multiple well-defined annular plaques with peripheral studded pustules with a collarette of scales on the (a) arm and (b) forearm.

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Figure 2a:

Hyperkeratosis, parakeratosis, mild to moderate acanthosis (black star) (Haematoxylin & eosin, 40x).

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Figure 2b:

Subcorneal neutrophilic microabscesses (black arrow), moderate to dense neutrophilic exocytosis (arrowhead). The superficial dermis shows mild to moderate perivascular lymphocytes, histiocytes, and neutrophils with edema (red star) (Haematoxylin & eosin, 100x).

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Figure 3:

Complete clearance of skin lesions post-treatment with cyclosporine.

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Pustular psoriasis is defined by neutrophilic infiltration into the epidermis, leading to the formation of sterile pustules. Its common subtypes include generalised pustular psoriasis (von Zumbusch type), acrodermatitis continua of Hallopeau, and palmoplantar pustulosis. Less common forms, such as the circinate or Lapière’s type, present with erythematous, scaly annular borders and peripheral pustules that evolve into desquamative lesions. They are characterised by recurrent, cyclic, gyrate plaques with marginal sterile pustules and moderate pruritus. This variant tends to follow a milder course in children and carries a favourable prognosis.^1,2 The differential diagnosis included subcorneal pustular dermatosis (SPD), IgA pemphigus (SPD variant), erythrokeratoderma, tinea imbricata, erythema annulare centrifugum (EAC), and ichthyosis linearis circumflexa of Netherton syndrome. Subcorneal pustular dermatosis is a chronic relapsing pustular disorder with superficial pustules mainly in flexural regions, histologically marked by subcorneal pustules with neutrophilic infiltrates. IgA pemphigus, a rare autoimmune vesicopustular disorder, involves intercellular IgA deposition, particularly in the SPD subtype, which targets desmocollin 1.³ Direct immunofluorescence performed was negative, ruling out IgA pemphigus. Erythrokeratoderma en cocarde was also considered, as it presents with concentric, rosette-like plaques that often remit in summer.⁴ However, the presence of pustules and typical histology excluded this diagnosis. Tinea imbricata was ruled out due to the chronicity, negative potassium hydroxide mount, and absence of fungal elements. Erythema annulare centrifugum features trailing scales and perivascular inflammation, but the pustular nature and relapsing course in our case were inconsistent with this diagnosis. Ichthyosis linearis circumflexa manifests as serpiginous, migratory erythematous patches with characteristic double-edged scales. It is rarely seen as an isolated skin condition and is most often a cutaneous feature of Netherton syndrome, which is caused by mutations in the SPINK5 gene, resulting in absent or reduced expression of the serine protease inhibitor LEKTI. Clinically, NS is characterised by congenital ichthyosiform erythroderma, trichorrhexis invaginata (TI), and a predisposition to atopic manifestations, which our patient did not have. Treatment of pustular psoriasis includes systemic agents such as retinoids, methotrexate, cyclosporine, and biologics targeting TNF-α, IL-12/23, IL-17, or IL-36. Our patient responded well to cyclosporine, which was later tapered off, and she is now stable on methotrexate, under regular dermatologic follow-up. Our case highlights the atypical presentation of annular and circinate variants of pustular psoriasis in a young adult female with persistence into adulthood, a pattern more commonly associated with a benign course in infants and children. Recognising this uncommon clinical trajectory is prudent, and clinicians should maintain a high index of suspicion while differentiating it from other genodermatoses and inflammatory dermatoses with overlapping clinical features, to facilitate timely and accurate diagnosis and management.