Injection site reactions (ISRs) are a local phenomenon defined as a constellation of symptoms, including swelling, erythema, pruritus, and pain around the site of injection. This article reviews the different aspects of ISRs, including their epidemiology and pathogenesis, and provides practical guidance to diagnose and treat such reactions. More focus is given to food and drug administration (FDA)‐approved biological agents and biosimilars, which are licensed mainly for the treatment of dermatological conditions, including psoriasis, atopic dermatitis, and chronic urticaria. ISRs are major complications of all FDA‐approved self‐injectable biological agents, both in adults and children, with studies showing an incidence rate of 0.5–40%. The article emphasizes that ISRs are not correlated with drug efficacy or development of antidrug antibodies. Therefore, misunderstanding of the pathophysiology of the ISRs, most of them not being allergic or immunogenic reactions, might result in unnecessary discontinuation of the treatment. Almost all local reactions to subcutaneously administered biological agents can be prevented by changing the injection techniques, patient education, and training.

Peroxisome proliferator‐activated receptors (PPARs) are abundantly expressed in human skin, with PPAR‐γ being the most intensively investigated isoform. In various ex vivo and in vivo models, PPAR‐γ‐mediated signalling has recently surfaced as an essential element of hair follicle (HF) development, growth and stem cell biology. Moreover, the availability of novel, topically applicable PPAR‐γ modulators with a favourable toxicological profile has extended the range of potential applications in clinical dermatology. In this review, we synthesize where this field currently stands and sketch promising future research avenues, focussing on the role of PPAR‐γ‐mediated signalling in the biology and pathology of human scalp HFs, with special emphasis on scarring alopecias such as lichen planopilaris and frontal fibrosing alopecia as model human epithelial stem cell diseases. In particular, we discuss whether and how pharmacological modulation of PPAR‐γ signalling may be employed for the management of hair growth disorders, for example, in scarring alopecia (by reducing HF inflammation as well as by promoting the survival and suppressing pathological epithelial‐mesenchymal transition of keratin 15 + epithelial stem cells in the bulge) and in hirsutism/hypertrichosis (by promoting catagen development). Moreover, we explore the potential role of PPAR‐γ in androgenetic alopecia, HF energy metabolism and HF ageing, and consider clinical perspectives that emanate from the limited data available on this so far. As this field of translational human hair research is still in its infancy, many open questions exist, for which we briefly delineate selected experimental approaches that promise to generate instructive answers in the near future.

Quantification of fatty vacuoles in the liver, with differentiation from lumina of liver blood vessels and bile ducts, is an example where the traditional semiquantitative pathology assessment can be enhanced with artificial intelligence (AI) algorithms. Using glass slides of mice liver as a model for nonalcoholic fatty liver disease, a deep learning AI algorithm was developed. This algorithm uses a segmentation framework for vacuole quantification and can be deployed to analyze live histopathology fields during the microscope-based pathology assessment. We compared the manual semiquantitative microscope-based assessment with the quantitative output of the deep learning algorithm. The deep learning algorithm was able to recognize and quantify the percent of fatty vacuoles, exhibiting a strong and significant correlation ( r = 0.87, P < .001) between the semiquantitative and quantitative assessment methods. The use of deep learning algorithms for difficult quantifications within the microscope-based pathology assessment can help improve outputs of toxicologic pathology workflows.