Maho Matsuo

Annular erythema is a nonspecific clinical sign arising from various conditions, including infections, cutaneous lymphomas, connective tissue diseases, and inflammatory dermatoses. Psoriasis vulgaris typically presents as sharply demarcated erythematous plaques with silvery scales; however, annular forms are rare and may complicate diagnosis. We report a nine-year-old girl with an annular erythematous lesion on the anterior chest that gradually expanded over two months, spreading to the extremities and trunk with mild pruritus. Despite suspicion of tinea corporis, repeated fungal tests were negative, and topical corticosteroids were ineffective. Skin biopsy showed marked hyperkeratosis, loss of the granular layer with parakeratosis, and subcorneal Munro's microabscesses; no fungal elements were found. Laboratory tests and imaging were unremarkable, and genetic screening for IL36RN and CARD14 found no pathogenic variants. A diagnosis of psoriasis vulgaris was made with a Psoriasis Area and Severity Index (PASI) score of 7.8. After failed topical treatment, systemic secukinumab therapy was initiated, leading to complete lesion resolution within two months. This case emphasizes the importance of considering psoriasis in the differential diagnosis of pediatric annular erythema and demonstrates the value of histopathology and biologics in managing atypical pediatric psoriasis.

A 49‐year‐old man with pemphigus vegetans (PVeg) relapsed several times due to cessation of therapy. At the age of 66, vegetative plaques developed at the left oral commissure following mechanical plucking of approximately 500 beard hairs. Treatment with prednisolone (20 mg/day) was continued but yielded no clinical improvement. Subsequently, rituximab (1000 mg twice, 2 weeks apart) led to a rapid decline of anti‐desmoglein 3 (Dsg3) autoantibody and clinical improvement. The lesion resolved after 18 months, and prednisolone was tapered without recurrence. Based on the site‐specific recurrence and chronicity, we hypothesized that tissue‐resident memory T (T _RM ) cells and high endothelial venules (HEV)‐like vessels contributed to disease persistence. Immunohistochemical analysis revealed a substantial presence of IL‐17A‐producing CD69 + ⁺ CD103 + ⁺ T _RM cells in the dermis. In addition, PNAd+ ⁺ HEV‐like vessels were increased, accompanied by infiltrates of B cells and plasma cells. Notably, Dsg3‐specific B cells were also detected, indicating that rituximab‐mediated B cell depletion likely contributed to lesion resolution in this case.

A 50‐year‐old man presented with a subcutaneous mass on the posterior neck. A skin biopsy suggested lipoma, leading to observation. Over the next 5 years, the tumor gradually enlarged. Clinical evaluation found the tumor to be a soft, mobile mass of 10 × 7 cm. Magnetic resonance imaging showed the lesion to be cystic, with hyperintense mural nodules on T2‐weighted sequences, and with scattered, hyperintense foci indicative of fatty components on T1‐weighted imaging. Fat‐suppressed contrast‐enhanced T1‐weighted imaging revealed moderately enhanced mural nodules. Surgical resection revealed a well‐circumscribed cystic mass containing fluid, surrounded by a fibrous capsule. We suspected spindle cell lipoma associated with fluid and performed a marginal resection. Gross examination showed a heterogeneous mixture of reddish‐brown and yellowish zones interspersed with fissures. Histological analysis revealed a leaf‐like or reticular pattern, with slender, spindle‐shaped cells and ropey collagens within a mucinous matrix, along with mature adipocytes. There were many irregular, branching, cleft‐like vascular spaces lined by flattened cells. Immunohistochemical staining revealed tumor cells positive for CD34 and negative for retinoblastoma protein. Luminal endothelial‐like cells showed positivity for D2‐40, CD31, and erythroblastosis transformation‐specific regulated gene 1. Based on these findings, the diagnosis of pseudoangiomatous spindle‐cell lipoma was confirmed, with the luminal endothelial‐like cells exhibiting characteristics of lymphatic endothelium.

A 60‐year‐old Japanese woman had a history of acneiform rashes and pruritus from age 20. She had sought medical attention at the age of 49 due to the progressive enlargement of the lesions. Despite various therapeutic interventions, including topical steroids and oral cyclosporine, the condition continued to worsen. Upon examination at age 60, erythematous areas with hyperkeratotic nodules were noted, and a dermoscopic evaluation revealed keratin plugs within the hair follicles. A histopathological analysis showed suprabasal acantholysis, with grains and corps ronds dispersed throughout the lesions. Genetic testing identified a non‐pathogenic variant in ATP2A2 , which effectively excluded Darier's disease. We made the final diagnosis of warty dyskeratomas (WD). Human papillomavirus was not implicated. Notably, immunohistochemical analyses revealed the overexpression of SERCA2, which further supported the diagnosis of WD rather than Darier's disease. WD is a rare, benign, dermatological condition that typically affects middle‐aged women and is often localized to the scalp. While histologically similar to Darier's disease, WD lacks the pathogenic mutations in ATP2A2 . Ultimately, the diagnosis of WD was confirmed in our patient through a comprehensive assessment of clinical, histopathological, and genetic findings.

An 89‐year‐old Japanese woman presented with erythroderma associated with significant scaling. A histological examination showed acanthosis with hyperkeratosis and hyperkeratinization of the hair follicles. Genetic analyses using DNA from the peripheral blood revealed heterozygous mutations in IL36RN (c.115+6T>C) and CARD14 c.2648G>A (p.Arg883His). Based on these findings, we diagnosed her with erythroderma attributable to autoinflammatory keratinization disease. She then developed more than 30 small, round, well‐defined, spots on her back and extremities that appeared histologically normal. We suspected that these spots might be revertant mosaicism. Immunohistochemical staining with p65, which is a component of nuclear factor kappa‐light‐chain‐enhancer of activated B cells (NF‐kB), revealed nuclear staining in epidermal keratinocytes in erythematous lesions, but not in the normal‐looking spots. However, mutations in IL36RN and CARD14 unexpectedly persisted in the epidermis and dermis of the normal‐looking spots.