Background: Alitretinoin, a pan-retinoid receptor agonist approved for chronic hand eczema, exhibits immunomodulatory effects that may benefit alopecia areata (AA). However, clinical evidence for its use in AA is limited. Objective: To evaluate alitretinoin's clinical efficacy and immunological mechanism in patients with AA. Methods: We reviewed retrospectively twenty-one patients with AA who were treated with alitretinoin, either as monotherapy (n=9) or add-on therapy (n=12). Treatment response was assessed using the Severity of Alopecia Tool (SALT) scores, and in vitro studies used human outer root sheath cells stimulated with interferon-γ and polyinosinic:polycytidylic acid to investigate the drug’s effects on inflammatory pathways. Results: Both groups showed significant reductions in SALT scores (p=0.04 and p=0.02, respectively). Patients with baseline SALT scores below 50 demonstrated superior improvement.Adverse events were mild, with headache (33.3%) and cheilitis (4.8%) being the most common. In vitro, alitretinoin suppressed interleukin-6 and tumor necrosis factor-α expression, decreased phosphorylation of signal transducer and activator of transcription (STAT) 1/STAT3, and downregulated major histocompatibility complex class I expression, suggesting restoration of hair follicle immune privilege. Conclusion Alitretinoin appears to be a safe and potentially effective treatment for patients with mild to moderate AA unresponsive to conventional therapies. Its role as a monotherapy or adjunctive option in selected cases warrants further investigation through larger controlled studies.

Background: Enlarged perivascular space (ePVS) is recently reported to be associated with cerebral small vessel disease (SVD) and Alzheimer’s disease (AD). The topographical location of ePVS may relate to the underlying pathology; basal ganglia (BG)-ePVS has been associated with cerebral vascular diseases and centrum semi-ovale (CSO)-ePVS associated with cerebral amyloid angiopathy (CAA). However, the effects of ePVS on various neurological conditions remain still controversial. To investigate the clinical relevance of ePVS in neurodegenerative diseases, we tested relationships between ePVS and cognition, markers of SVD, vascular risk factors, or amyloid pathology. Methods: We retrospectively reviewed 292 patients (133 AD dementia, 106 mild cognitive impairment, 39 other neurodegenerative diseases, 14 subjective cognitive decline) who underwent both amyloid positron emission tomography and brain magnetic resonance imaging. Vascular risk factors and cognitive tests results were collected. The ePVS in the BG and CSO, SVD markers and the volume of white matter hyperintensities were measured. Results: There were no significant differences in the severity and distribution of ePVS among clinical syndromes. Both BG- and CSO-ePVS were not related to cognitive function. Patients with lacunes were more likely to have high-degree BG-ePVS. High degree CSO-ePVS had an odds ratio (OR) for amyloid positive of 2.351, while BG-ePVS was a negative predictor for amyloid pathology (OR, 0.336). Conclusions Our findings support that ePVS has different underlying pathologies according to the cerebral topography. BG-ePVS would be attributed to hypertensive angiopathy considering the relation with SVD markers, whereas and CSO-ePVS would be attributed to CAA considering the association with amyloid pathology.