Kawasaki disease (KD) is a systemic vasculitis primarily affecting children, but its presentation can be highly variable, especially in young infants. While KD is classically associated with a polymorphous rash, annular or targetoid rashes are rare and can contribute to diagnostic uncertainty. Additionally, neurological complications such as seizures and aseptic meningitis are uncommon, further complicating recognition. We present a case with these atypical features, which closely mimic other conditions, including meningoencephalitis and reactive infection mucocutaneous eruption in children.

Urticaria multiforme (UM) is a benign hypersensitivity reaction of early childhood characterized by transient annular urticarial plaques with dusky centers and acral edema. Although self-limited, UM is frequently misdiagnosed as serum sickness-like reaction (SSLR), erythema multiforme (EM), or urticarial vasculitis due to overlapping features such as fever, edema, and inflammatory laboratory abnormalities. Diagnostic uncertainty may therefore lead to extensive investigations, hospitalization, and unnecessary systemic corticosteroid therapy. A three-year-old male with a history of atopic dermatitis presented with decreased oral intake, lethargy, fever, and intermittent erythematous wheals associated with swelling of the feet and extremities. Initial evaluation revealed influenza A (H3) infection, thrombocytosis, and mildly elevated C-reactive protein. Extensive diagnostic evaluation, including multiple imaging studies and laboratory investigations, was largely unremarkable except for preserved complement levels. Due to concern for a serum sickness-like reaction, systemic corticosteroids were initiated. The dermatology consultation subsequently favored urticaria multiforme based on the transient nature of lesions lasting less than 24 hours, absence of mucosal involvement or palpable purpura, preserved complement levels, and progressive clinical improvement. The patient was managed with antihistamines and supportive care, with complete resolution of fever, edema, and urticarial lesions prior to discharge after a hospital course of six days. This case highlights influenza-associated urticaria multiforme presenting with fever and mild inflammatory marker elevation, closely mimicking immune complex-mediated disease. Recognition of lesion duration, morphology, and complement preservation is essential for accurate diagnosis and to prevent unnecessary immunosuppressive therapy.

Secondary syphilis is renowned for its ability to mimic a wide range of dermatologic and systemic diseases, including vasculitides. Misinterpretation of its cutaneous manifestations can delay appropriate therapy and expose patients to unnecessary immunosuppression. We report the case of a young female who presented with an acute, maculopapular, and annular rash initially affecting the upper body, including the back, chest, and upper limbs, followed by involvement of the lower body. It was preceded by redness and inflammation of her eyes. Initial clinical evaluation supported a diagnosis of cutaneous small-vessel vasculitis, and systemic vasculitis was strongly suspected. However, an extended history revealed recent unprotected sexual contact a few weeks before the symptoms started. Serologic testing demonstrated positive non-treponemal and treponemal tests consistent with secondary syphilis. The patient was treated with intravenous ceftriaxone, resulting in rapid resolution of the rash and improvement of her symptoms, with an appropriate decline in non-treponemal titers on follow-up. This case illustrates how secondary syphilis can present with a vasculitis-appearing rash clinically and underscores the need to include syphilis in the diagnostic workup of small-vessel vasculitis. Routine sexual history-taking and early syphilis serology in adults with an unexplained vasculitis rash may prevent diagnostic delay, inappropriate immunosuppression, and ongoing transmission.

Kawasaki disease (KD) and multisystem inflammatory syndrome in children (MIS-C) are pediatric inflammatory conditions with overlapping mucocutaneous features that may complicate early diagnosis. We performed a narrative review of the literature to characterize and compare cutaneous manifestations reported in children with KD and MIS-C and to assess their diagnostic relevance. Published studies describing dermatologic findings in patients aged 0-18 years were reviewed. The analysis revealed a broad heterogeneity of skin manifestations in both conditions, ranging from classic polymorphous rash and acral erythema to atypical presentations, including annular, psoriasiform, vesiculobullous, urticarial, and erythema nodosum-like lesions. Reactivation at Bacillus Calmette-Guérin vaccination sites and associated mucocutaneous findings, such as conjunctivitis and oral changes, emerged as supportive diagnostic clues, particularly for incomplete KD. Considerable overlap in cutaneous phenotypes between KD and MIS-C was observed, especially in patients with persistent fever and systemic inflammation, highlighting the risk of diagnostic delay. These findings underscore the importance of recognizing atypical dermatologic patterns as part of an integrated diagnostic approach, as delayed identification may increase the risk of cardiovascular complications. Early recognition of cutaneous clues can support timely initiation of immunomodulatory therapy and improve clinical outcomes.

IgA-mediated Anti-Laminin-γ1 (p200) pemphigoid is a rare subtype of subepidermal autoimmune blistering disease (AIBD) characterized by IgA autoantibodies targeting the laminin γ1 chain, a 200 kDa protein located at the dermal-epidermal junction. Patients typically exhibit skin-dominant blistering lesions, also mucosal involvement has been reported. We report a 73-year-old male patient diagnosed with IgA-mediated anti-Laminin-γ1 (p200) pemphigoid. He initially presented with prominent palmoplantar blisters erosions on the eyelids, lips and face, accompanied by mild pruritus. Skin biopsy demonstrated hyperkeratosis, parakeratosis, acanthosis, subepidermal blister formation, and mild perivascular lymphocytic infiltration in the superficial dermis. Direct immunofluorescence showed C3 deposits on the basement membrane. The patient was initially treated successfully with methylprednisolone. During the second recurrence, he presented with annular erythema topped with blisters and erosions on the lips. Comprehensive pemphigus and pemphigoid antibodies panel test showed Laminin γ1 IgA with a titer of 1:10. The rash recurred when corticosteroids were tapered. The patient was then treated with Stapokibart (CM310) in combination with corticosteroids, leading to complete resolution of the skin lesions and successful tapering of the corticosteroids. This case represents the first successful treatment of IgA-mediated anti-Laminin-γ1 (p200) pemphigoid using Stapokibart in combination with corticosteroid.

Primary cutaneous B-cell lymphoma most commonly presents as solitary or multiple violaceous papules, nodules, or plaques depending on the specific subtype. It tends to have an aggressive clinical course. Secondary cutaneous involvement of systemic or nodal lymphoma also needs to be excluded. We describe a unique case of a 73-year-old man with presentation as striking annular and arcuate lesions clinically and histologically mimicking an interstitial granulomatous dermatitis, such as granuloma annulare. Close scrutiny of the interstitial infiltrate on histology and adjunctive immunostaining established the diagnosis as diffuse large B-cell lymphoma (DLBL). This is the first description of B-cell lymphoma mimicking interstitial granuloma annulare clinically and histologically. Cutaneous T-cell lymphoma, in particular the "interstitial" variant of mycosis fungoides, is reported to closely mimic interstitial granuloma annulare. Although the skin histology suggested high grade features,due to the unusual indolent clinical presentation, the patient was monitored clinically.Five years after initial presentation, the patient developed a large fungating skin tumor on the chest wall also confirmed as DLBL. Six cycles of R-CHOP chemotherapy led to complete resolution of the chest lesion and rash. Eighteen months after completion of chemotherapy, he presented to hospital with left-sided weakness. A CT scan revealed a right temporal lobe mass, radiologically most likely lymphoma. The patient declined further treatment and died shortly afterward. This case highlights the importance of long-term follow-up of patients with DLBL, even with a seemingly indolent initial clinical presentation.