What is "eczema"?

Eczema is the most common category of inflammatory skin disorders as dermatologists see many patients with eczematous diseases in daily practice. It is characterized by the three major morphological features: multiple-pinpoint condition, polymorphism, and itch. To describe polymorphism, "eczema triangle" has been used in German/Japanese dermatology. The multiple pinpoints correspond to numerous tiny foci from which individual papules/vesicles arise. The polymorphism betrays composition of erythema, papule, seropapule, vesicle, pustule, scale, and crust, which are seen in acute eczema. Meanwhile, chronic eczema is represented by lichenification and hyperpigmentation, and possibly by hypopigmentation. In acute eczema, spongiosis is associated with overproduction of hyaluronic acid, secretion of self-protective galectin-7, and decreased expression of E-cadherin. In the upper dermis, Th1/Tc1 or Th2/Tc2, and additional Th17, Th22, and/or Tc22 infiltrate, depending on each eczematous disease. Innate lymphoid cells are also involved in the formation of eczema. In chronic eczema, periostin contributes to remodeling of inflammatory skin with dermal fibrosis, and epidermal melanogenesis and dermal pigment deposition result in hyperpigmentation. Finally, eczematous diseases are potentially associated with increased risk of comorbidities, including not only other allergic diseases but also coronary heart disease and mental problems such as depression. Although the original word for eczema is derived from old Greek "ekzein," eczema remains a major target of modern science and novel therapies.

DiGeorge syndrome presenting with palmoplantar pustules: Comparative analysis of serum IL-22, NETs and IL-8 with usual palmoplantar pustulosis.

DiGeorge syndrome, also known as 22q11.2 deletion syndrome, shows cellular immunodeficiency due to by thymic hypoplasia and hypocalcemia caused by hypoparathyroidism. It was reported that erythrodermic psoriasis occurred in a patient with 22q11 deletion syndrome. Here, we report the first case of DiGeorge syndrome presenting with a severe palmoplantar pustulosis (PPP)-like eruption with extra-palmoplantar lesions on the distal limbs. Given that PPP is a subtype of pustular psoriasis, the pustular eruption may be associated with DiGeorge syndrome. We measured serum levels of citrullinated histone H3 (CitH3), a representative marker of neutrophil extracellular traps, interleukin (IL)-8, and IL-22 and compared them with nine cases of typical PPP. In the PPP patients, the three markers were higher than in healthy subjects with significant correlations between CitH3 and IL-8/IL-22. In our patient, CitH3, IL-8, and IL-22 were also high, and IL-22 was remarkably elevated compared with the PPP patients. Our case suggests that a certain T cell abnormality associated with DiGeorge syndrome induces IL-22 overproduction, leading to the PPP-like eruption with extra- palmoplantar lesions.

How Do Classical Subtypes Correspond to Endotypes in Atopic Dermatitis?

Since atopic dermatitis (AD) is a heterogeneous condition, the subtyping of AD is a crucial issue. The classical subtypes of AD are represented by extrinsic and intrinsic subtypes, European-American and Asian subtypes, and adult and pediatric subtypes. While the subtyping of AD was historically conducted based on the phenotype, recent findings on the mechanisms of AD have revealed the importance of the endotype, which can characterize individual patients more accurately. Considering the current development of AD therapies, AD endotyping is a prerequisite for a personalized therapeutic choice. Endotypes of AD can be stratified from different viewpoints, including cytokine expression patterns, allergen properties, epidermal barrier conditions, ceramide variation, the involvement of innate immunity, and serum biomarkers. Among them, the cytokine-based endotype seems to be the most useful one and is categorized into type 2 cytokine (IL-4, IL-13 and IL-31)-high, type 1 cytokine (IFN-γ)-high, and/or type 3 cytokine (IL-22 and IL-17)-high, or mixed subtypes. Recently proposed biomarker endotyping aims at individualized treatment options, although the daily clinical use of endotypes is a future issue. To better understand the endotypes for clinicians, attempts to adjust each of the classical subtypes to endotypes are required. This review will discuss the correspondence of the classical subtypes to the various endotypes that have recently been proposed.