CADASIL is a small vessel disease caused by mutations in NOTCH3 that lead to an odd number of cysteines in the EGF-like repeat domain, causing protein misfolding and aggregation. The main symptoms are migraine, psychiatric disturbances, recurrent strokes and dementia, being executive function characteristically impaired. The molecular pathways altered by this receptor aggregation need to be studied further. A genome-wide transcriptome study (four cases paired with three healthy siblings) was carried out, in addition to a qRT-PCR for validation purposes (ten new cases and eight new controls). To study the expression profile by cell type of the significant mRNAs found, we performed an in situ hybridization (ISH) (nine cases and eight controls) and a research in the Single-nuclei Brain RNA-seq expression browser (SNBREB). Pathway analysis enrichment was carried out with Gene Ontology and Reactome. Neuropsychological tests were performed in five of the qRT-PCR cases. The two most significant differentially expressed mRNAs (BANP, p-value = 7.23 × 10–4 and PDCD6IP, p-value = 8.36 × 10–4) were selected for the validation study by qRT-PCR. Additionally, we selected two more mRNAs (CAMK2G, p-value = 4.52 × 10–3 and E2F4, p-value = 4.77 × 10–3) due to their association with ischemic neuronal death. E2F4 showed differential expression in the genome-wide transcriptome study and in the qRT-PCR (p = 1.23 × 10–3), and it was upregulated in CADASIL cases. Furthermore, higher E2F4 expression was associated with worse executive function (p = 2.04 × 10–2) and attention and information processing speed (IPS) (p = 8.73 × 10–2). In situ hibridization showed E2F4 expression in endothelial and vascular smooth vessel cells. In silico studies indicated that E2F4 is also expressed in brain endothelial cells. Among the most significant pathways analyzed, there was an enrichment of vascular development, cell adhesion and vesicular machinery terms and autophagy process. E2F4 is more highly expressed in the skin biopsy of CADASIL patients compared to controls, and its expression is present in endothelial cells and VSMCs. Further studies are needed to understand whether E2F4 could be useful as a biomarker, to monitor the disease or be used as a therapeutic target.

A 45-year-old woman presented with a solitary breast nodule that histologically corresponded to a dense dermal/ subcutaneous infiltration of atypical cytotoxic T-lymphocytes (CD3 + , CD8 + , CD56 + , TIA-1+, CD5 2 , CD4 2 , CD30 2 , EBV 2 ), resembling subcutaneous panniculitic T-cell lymphoma. The presence of TCRd gene rearrangement and the absence of bF1 expression let to suspect the diagnosis of primary cutaneous gdT-cell lymphoma. As a consequence of jejunum perforation following chemotherapy treatment, a mucosal atypical lymphoid infiltration with marked epitheliotropism was observed in the resected intestinal sample, and the diagnosis of monomorphic epitheliotropic intestinal T-cell lymphoma (MEITL) was finally established. Disease progression appeared with multiple erythematous plaques showing a dense lichenoid atypical cytotoxic T-cell infiltrate with intense epidermotropism, mimicking primary cutaneous epidermotropic aggressive CD8 + T-cell lymphoma. MEITL is an uncommon and aggressive peripheral T-cell lymphoma that often presents in adults with gastrointestinal symptoms. Secondary cutaneous involvement is a rare phenomenon that may show clinicopathologic and immunohistochemical features that overlap with different subtypes of primary cutaneous cytotoxic T-cell lymphomas. In the absence of gastrointestinal symptoms, the diagnosis may be challenging, and only the evidence of underlying MEITL may allow to establish the definite diagnosis.

Colony‐stimulating factor 1 receptor (CSF1R) inhibitors represent a new class of immune‐modulatory drugs, mostly investigated in clinical trials in different malignant neoplasms. Four patients, diagnosed with recurrent or advanced malignant neoplasm and treated with a combination of anti‐programmed death ligand 1 and anti‐CSF1R monoclonal antibodies, developed an asymptomatic cutaneous eruption characterized by an ill‐defined pseudoedematous to waxy diffuse infiltration with a reticular cobblestone‐like pattern. Histopathological examination revealed diffuse mucin deposition involving the superficial and mid‐dermis with fragmented and scattered elastic fibers. The exact pathogenic mechanisms implicated in the development of mucin deposits in patients treated with CSF1R inhibitors remain to be elucidated. A reduced degradation and clearance of components of the extracellular matrix by macrophages secondary to CSF1 pathway inhibition may be hypothesized. Shredding and fragmentation of elastic fibers may be a result of the increased accumulation of mucopolysaccharides. This observation illustrates the new spectrum of skin‐related toxicities secondary to new targeting therapies. This may contribute to a better understanding of the underlying pathogenic mechanisms in skin diseases characterized by a persistent dermal glycosaminoglycan deposition.

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