Nummular eczema (NE) and atopic dermatitis (AD) share clinical features, yet their skin microbiomes remain insufficiently characterized. This exploratory pilot study evaluated the taxonomic composition and functional potential of the skin microbiome across NE, a mixed NE/AD phenotype (Mixed NE_AD), and AD using shotgun metagenomics. Lesional swabs from Korean patients with NE (n = 8), Mixed NE_AD (n = 6), and AD (n = 5) were sequenced to assess microbial diversity, taxonomy, and functional pathways. Staphylococcus aureus predominated across all groups. NE samples were characterized by the higher relative abundance of environmental taxa, wherein Delftia acidovorans was observed only in NE samples in this cohort, and Kocuria palustris diminished sequentially across the Mixed NE_AD and AD phenotypes. Mixed NE_AD exhibited greater intra-genus Staphylococcus diversity. Despite non-significant overall diversity differences, partial ecological separation was noted. Functionally, descriptive differences in metabolic potential were observed, with NE showing trends toward biosynthetic and oxidative stress-associated pathways and AD showing trends toward degradation-related pathways. Mixed NE_AD showed intermediate characteristics. Although these differences did not reach statistical significance after correction for multiple testing, these findings provide preliminary evidence for microbiome-based stratification of eczematous disorders, warranting larger cohort validation.

Activated phosphoinositide-3-kinase delta syndrome (APDS) is a rare primary immunodeficiency caused by gain-of-function mutations in the PIK3CD gene, resulting in the hyperactivation of the PI3K-Akt-mTOR pathway and subsequent immune dysregulation. Although recurrent sinopulmonary infections are typical, cutaneous manifestations remain poorly characterized. Nummular dermatitis is an uncommon presentation in this context and may reflect the underlying inflammatory imbalance. A 17-year-old female patient with genetically confirmed APDS (heterozygous PIK3CD c.3061G>A; p.Glu1021Lys) presented with erythematous papules that evolved into tense bullae on the lower limbs following an insect bite. Over subsequent weeks, multiple well-defined, coin-shaped eczematous plaques developed on the extremities and trunk, consistent with nummular dermatitis. The patient had a history of recurrent respiratory infections, chronic sinusitis, and otitis media, managed with intravenous immunoglobulin and prophylactic antibiotics. Topical betamethasone with fusidic acid and oral antihistamines produced partial improvement, though intermittent relapses occurred during follow-up. No systemic symptoms or new infectious complications were identified. This case represents an unusual dermatologic manifestation of APDS, where a minor external trigger led to persistent eczema-like lesions. Dysregulated PI3K-Akt-mTOR signaling may amplify local inflammation and impair epidermal barrier recovery. Recognition of atypical or chronic dermatitis in immunodeficient patients is crucial for early diagnosis, targeted treatment, and multidisciplinary management. Reporting such cases expands the clinical spectrum of APDS and underscores the importance of considering immune dysregulation in persistent cutaneous disorders.

Background: Atopic dermatitis (AD) is a chronic, relapsing inflammatory dermatosis that is characterized by pruritus, xerosis, and age-dependent clinical heterogeneity. Accurately diagnosing AD remains challenging due to the absence of specific biomarkers and the broad spectrum of conditions that may mimic its presentation. A wide range of inflammatory, infectious, and genetic disorders resemble AD, including seborrheic dermatitis, psoriasis, contact dermatitis, scabies, dermatophytosis, and nummular eczema, as well as rare immunodeficiency and metabolic conditions. This review summarizes the evolution of the clinical features of pediatric AD across infancy, childhood, and adolescence, with a focus on key differential diagnoses. Recognizing age-specific patterns and potential mimickers is essential for improving diagnostic accuracy and guiding appropriate management in pediatric AD. Methods: This study was designed as a narrative review. A structured literature search was conducted of PubMed/MEDLINE for studies published between January 2001 and March 2026 using predefined keywords related to AD, childhood, diagnosis, and differential. Clinical trials, randomized controlled trials, systematic reviews, meta-analyses, and guidelines or consensus documents were included. Studies focusing exclusively on adults or lacking clinical relevance were excluded. A qualitative synthesis was performed due to the heterogeneity in study designs and outcomes. Results: This review demonstrates that pediatric atopic dermatitis exhibits marked age-dependent clinical heterogeneity, with distinct morphological features and lesion distribution patterns across infancy, childhood, and adolescence. Furthermore, the substantial clinical overlap with a broad spectrum of inflammatory, infectious, and genetic disorders-combined with the absence of specific diagnostic biomarkers-significantly complicates accurate differential diagnosis and increases the risk of misclassification. Conclusions: The recognition of age-specific patterns and potential mimickers is essential for improving diagnostic accuracy and guiding appropriate management in pediatric AD.

Background Tinea corporis is a common superficial fungal infection caused by dermatophytes. It typically presents as well-defined, pruritic, annular papules and plaques with central hypopigmentation. The differential diagnosis includes pityriasis rosea, nummular dermatitis, plaque psoriasis, tinea versicolor, granuloma annulare, and discoid lupus. This article compares different presentations of tinea corporis in various skin types as classified by the Fitzpatrick scale. Recognizing varying presentations of tinea in patients of different skin tones will aid in early and appropriate diagnosis and treatment.

Paraphenylenediamine (PPD) is an aromatic amine that was first manufactured in Germany by Hofmann in 1833. It is primarily employed for its antioxidant and staining properties and is found in rubber goods, printer ink, photographic supplies, textiles and footwear, henna tattoos, and hair dyes. As it is a prehapten that can cross the skin barrier easily, it can be detected in plasma, urine, and faeces after application of hair dye within half an hour. The molecular properties of PPD allow hair dye to effectively permeate the skin, resulting in sensitisation and the eventual development of allergic contact dermatitis. Redness, pain, pruritus, dryness, prickling sensation, burning or tingling sensation, and discomfort are some of the symptoms of hair dye dermatitis. Clinically, allergic reactions to PPD may vary from localised lesions, such as eyelid eczema, nummular eczema, or hand eczema, to disseminated forms, such as airborne contact dermatitis, prurigo-nodularis-like, or erythroderma-like. Systemic contact dermatitis (SCD) is a severe, delayed immune-mediated reaction (type IV hypersensitivity reaction) to PPD, a common ingredient in hair dyes and temporary "black henna" tattoos, causing widespread eczema, intense itching, redness, swelling, and sometimes even asthma-like symptoms or lymph node swelling, occurring far beyond the direct contact area after initial sensitization, and requires strict avoidance of PPD in all forms. This is a case of a woman who presented with symmetrical drug-related intertriginous and flexural exanthema (SDRIFE)-like features, a type of SCD post hairdye application, but without any history of drug intake that is relevant for Baboon syndrome (synonymous with SDRIFE).

Eczema is an inflammatory skin condition that affects individuals of all ages worldwide. Patients may develop various forms of eczema, including atopic dermatitis, contact dermatitis, which is often associated with an allergic response to various stimuli, dyshidrotic eczema which develops on the palms and soles, asteatotic dermatitis that predominantly occurs in elderly patients, nummular eczema characterized by its cylindrical shape lesions and seborrheic dermatitis often located on patient's scalps, back, face and chest. Extensive studies have been conducted on atopic dermatitis, however, limited information such as their etiology, effect on the immune system and potential treatments are available on the other types of eczema. The socioeconomic impacts of eczema include the cost of conventional treatments such as corticosteroids, immunosuppressive agents and phototherapy, expenses related to specialists' consultation and the effect on work and school productivity. The impact of atopic dermatitis on patients' quality of life, social functioning and individual healthcare expenses has been extensively studied in other countries but remains underreported in South Africa. Reports have estimated the annual direct and indirect costs in Australia, the United Kingdom and the United States, however reports are limited for South Africa. This study aimed to provide information on the different types of eczema's etiology, their respective socioeconomic impact in South Africa in correlation to the above mentioned inflated yearly cost, and conventional, targeted and alternative treatments commercially available. Several knowledge gaps were identified in this study, including the limited availability of information on asteatotic dermatitis, dyshidrotic dermatitis and nummular eczema, the effect most commercially available treatments have on other eczema subtypes and an in-depth review of the socioeconomic impact of eczema within the African continent.

Atopic dermatitis and contact dermatitis are among the most common dermatologic conditions encountered by the primary care clinician. Their presentation varies and can mimic infectious and other noninfectious conditions, making a thorough history essential, with particular emphasis on exposure to environmental and occupational irritants, as well as recognition of commonly affected sites. For all of these conditions, control of symptoms is often the goal of treatment, starting with general supportive care measures like frequent emollient use and often relying on topical steroidal and nonsteroidal agents as first-line therapies.

Although dermatological manifestations are common in hepatitis C virus (HCV) infection, nummular eczema is rarely reported in this context. We describe the case of a 73-year-old man with a seven-month history of pruritic lesions on the posterior thorax, unresponsive to symptomatic treatment. Physical and dermoscopic examination revealed well-demarcated, coin-shaped plaques with peripheral erythema and fine desquamation. Histopathology confirmed chronic inflammatory dermatitis. Laboratory tests showed elevated transaminases and high HCV viral load. The patient had a history of blood transfusion two decades prior but no prior HCV diagnosis. He was treated with a 12-week course of glecaprevir/pibrentasvir, which resulted in complete resolution of skin lesions and normalization of liver enzymes within one month. No adverse events were recorded. This case highlights the importance of recognizing atypical dermatological signs as possible early indicators of HCV infection and supports the effectiveness of direct-acting antivirals in resolving both hepatic and extrahepatic manifestations.