Atopic disease, including atopic dermatitis (eczema), allergy and asthma, has increased in frequency in recent decades and now affects approximately 20% of the population in the developed world. Twin and family studies have shown that predisposition to atopic disease is highly heritable. Although most genetic studies have focused on immunological mechanisms, a primary epithelial barrier defect has been anticipated. Filaggrin is a key protein that facilitates terminal differentiation of the epidermis and formation of the skin barrier. Here we show that two independent loss-of-function genetic variants (R510X and 2282del4) in the gene encoding filaggrin (FLG) are very strong predisposing factors for atopic dermatitis. These variants are carried by approximately 9% of people of European origin. These variants also show highly significant association with asthma occurring in the context of atopic dermatitis. This work establishes a key role for impaired skin barrier function in the development of atopic disease.

Ichthyosis vulgaris (OMIM 146700) is the most common inherited disorder of keratinization and one of the most frequent single-gene disorders in humans. The most widely cited incidence figure is 1 in 250 based on a survey of 6,051 healthy English schoolchildren. We have identified homozygous or compound heterozygous mutations R501X and 2282del4 in the gene encoding filaggrin (FLG) as the cause of moderate or severe ichthyosis vulgaris in 15 kindreds. In addition, these mutations are semidominant; heterozygotes show a very mild phenotype with incomplete penetrance. The mutations show a combined allele frequency of approximately 4% in populations of European ancestry, explaining the high incidence of ichthyosis vulgaris. Profilaggrin is the major protein of keratohyalin granules in the epidermis. During terminal differentiation, it is cleaved into multiple filaggrin peptides that aggregate keratin filaments. The resultant matrix is cross-linked to form a major component of the cornified cell envelope. We find that loss or reduction of this major structural protein leads to varying degrees of impaired keratinization.

Background The multi-morbid burden and use of systemic immunosuppressants in people with psoriasis may confer greater risk of adverse COVID-19 outcomes but data are limited. Objective Characterize the course of COVID-19 in psoriasis and identify factors associated with hospitalization. Methods Clinicians reported psoriasis patients with confirmed/suspected COVID-19 via an international registry, PsoProtect. Multiple logistic regression assessed the association between clinical/demographic characteristics and hospitalization. A separate patient-facing registry characterized risk-mitigating behaviours. Results Of 374 clinician-reported patients from 25 countries, 71% were receiving a biologic, 18% a non-biologic and 10% no systemic treatment for psoriasis. 348 (93%) fully recovered from COVID-19, 77 (21%) were hospitalized and nine (2%) died. Increased hospitalization risk was associated with older age (multivariable-adjusted OR 1.59 per 10 years, 95% CI 1.19-2.13), male sex (OR 2.51, 95% CI 1.23-5.12), non-white ethnicity (OR 3.15, 95% CI 1.24-8.03) and comorbid chronic lung disease (OR 3.87, 95% CI 1.52-9.83). Hospitalization was more frequent in patients using non-biologic systemic therapy than biologics (OR 2.84, 95% CI 1.31-6.18). No significant differences were found between biologic classes. Independent patient-reported data (n=1,626 across 48 countries) suggested lower levels of social isolation in individuals receiving non-biologic systemic therapy compared to biologics (OR 0.68, 95% CI 0.50-0.94). Conclusion In this international moderate-severe psoriasis case series, biologics use was associated with lower risk of COVID-19-related hospitalization than non-biologic systemic therapies, however further investigation is warranted due to potential selection bias and unmeasured confounding. Established risk factors (being older, male, non-white ethnicity, comorbidities) were associated with higher hospitalization rates. Clinical Implications We identify risk factors for COVID-19-related hospitalization in psoriasis patients, including older age, male sex, non-white ethnicity and comorbidities. Use of biologics was associated with lower hospitalization risk than non-biologic systemic therapies.

SLURP1 is a secreted member of the LY6/PLAUR protein family. Mutations in the SLURP1 gene are the cause of Mal de Meleda (MDM), a rare autosomal recessive genetic disease, characterized by inflammatory palmoplantar keratoderma. In this study, we have analyzed the expression of SLURP1 in normal and MDM skin. SLURP1 was found to be a marker of late differentiation, predominantly expressed in the granular layer of skin, notably the acrosyringium. Moreover, SLURP1 was also identified in several biological fluids such as sweat, saliva, tears, and urine from normal volunteers. In palmoplantar sections from MDM patients, as well as in their sweat, mutant SLURP1, including the new variant R71H-SLURP1, was either absent or barely detectable. Transfected human embryonic kidney 293T cells expressed the MDM mutant SLURP1 containing the single amino-acid substitution G86R but did not tolerate the MDM mutation W15R located in the signal peptide. Thus, most MDM mutations in SLURP1 affect either the expression, integrity, or stability of the protein, suggesting that a simple immunologic test could be used as a rapid screening procedure.

13-cis retinoic acid exerts its specific activity on human sebocytes through selec-tive intracellular isomerization to all-trans retinoic acid and binding to retinoid acid receptors. J Invest Dermatol 115:321-7