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Genome‐wide association studies have identified more than 60 susceptibility loci for psoriasis, highlighting the role of genetics in psoriasis development. Although the HLA region is suggested as the most prominent susceptibility locus, the role of the HLA haplotype in the development of psoriasis is unclear. The aim of this study is to investigate how HLA haplotype changes affect the onset of psoriasis and which HLA haplotypes are associated with the development of psoriasis. A longitudinal, retrospective case series study of children was conducted at Tohoku University Hospital in Japan, between November 1981 and October 2020. We evaluated a total of 378 pediatric patients who underwent hematopoietic stem cell transplantation in the Department of Pediatrics. The background of these patients and their HLA haplotypes before and after transplantation was assessed. Among the 378 cases, aged 0–22 years old (median age 6) identified, 117 cases received autologous transplantation, 260 cases received allogeneic transplantation, and one case received syngeneic transplantation. Only two cases developed de novo psoriasis, and these cases had acquired HLA‐B46‐Cw1 after allogeneic transplantation. Others who had HLA‐B46‐Cw1 before and after allogeneic transplantation did not develop psoriasis. Our findings suggest that the HLA‐B46 and HLA‐Cw1 combination contributes to the development of psoriasis in this Asian population. [ABSTRACT FROM AUTHOR]

A case of atopic dermatitis (AD) with X‐linked agammaglobulinemia (XLA), which is one of the primary immunodeficiency diseases, is reported. A 12‐year‐old boy had suffered from dry skin and recurrent itchy eruptions since he was 2 years old, and he was diagnosed as having XLA at the age of 4 years. His total immunoglobulin (Ig)E level was 7 IU/mL, even with regular Ig replacement therapy. Furthermore, filaggrin (FLG) mutations known in the Japanese population were not found. His skin lesions were well controlled by the application of a mild‐class topical steroid and a moisturizer, though he developed folliculitis due to Staphylococcus aureus infection during treatment with a strong‐class topical steroid. This case suggests that the FLG mutation and IgE‐mediated sensitization are not necessary to induce AD skin manifestation. [ABSTRACT FROM AUTHOR]

Abstract: We report a 9‐year‐old Japanese female patient with atopic dermatitis associated with idiopathic thrombocytopenic purpura. She demonstrated high serum immunoglobulin (Ig)E and IgE specific to several environmental allergens, but extremely low serum thymus and activation‐regulated chemokine (TARC) levels regardless of the disease progression. This case suggests platelets as the main source of serum TARC. [ABSTRACT FROM AUTHOR]