The molecular phenotype of AA AD skin is characterized by attenuated Th1 and Th17 but similar Th2/Th22-skewing to EA AD. Our data encourages a personalized medicine approach accounting for phenotype-specific characteristics in future development of targeted therapeutics and clinical trial design for AD.

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Summary Background Frontal fibrosing alopecia (FFA) is a scarring alopecia with unclear pathogenesis and a progressive course. The disease has a major impact on patients’ quality of life and there is a lack of effective treatment to halt disease progression. Methods We profiled lesional and nonlesional scalp biopsies collected in 2017 from patients with FFA (n = 12) compared with scalp biopsies from patients with alopecia areata (AA) (n = 8) and controls (n = 8) to evaluate gene and protein expression, including the primary outcome (CXCL9). We determined significant differences between biomarkers using a two‐sided Student's t‐test adjusting P‐values by false discovery rate. Results Significant increases were seen in CD8+ cytotoxic T cells, CD11c+ dendritic cells, CD103+ and CD69+ tissue‐resident memory T cells in FFA and AA vs. control scalp (P < 0·05), with corresponding significantly upregulated granzyme B mRNA, particularly in FFA (P < 0·01). In AA, cellular infiltrates were primarily concentrated at the bulb, while in FFA these were mainly localized at the bulge. FFA demonstrated significant upregulation of T helper 1/intereferon (IFN) (IFN‐γ, CXCL9/CXCL10), the Janus kinase/signal transducers and activators of transcription (JAK‐STAT) pathway (STAT1, JAK3) and fibrosis‐related products (vimentin, fibronectin; P < 0·05), with no concomitant downregulation of hair keratins and the T‐regulatory marker, forkhead box P3, which were decreased in AA. The stem cell markers CD200 and K15 demonstrated significantly reduced expression only in FFA (P < 0·05). Conclusions These data suggest that follicular damage and loss of stem cells in FFA may be mediated through immune attack in the bulge region, with secondary fibrosis and reduced but still detectable stem cells. JAK/STAT‐targeting treatments may be able to prevent permanent follicular destruction and fibrosis in early disease stages.

Verrucous psoriasis is a variant of psoriasis that presents with wartlike clinical features and overlapping histologic features of verruca and psoriasis. The disease typically arises in patients with established psoriasis but can occur de novo. We report the case of an 80-year-old man with a history of hypertension and coronary artery disease who presented with a rash characterized by multiple asymptomatic plaques with overlying verrucous nodules on the left side of the body. The lesions appeared shortly after coronary artery bypass surgery with a saphenous vein graft.

Interdigitating dendritic cell sarcomas (IDCSs) are aggressive tumors of dendritic cells, often presenting with lymphadenopathy. Fewer than 10 cases of primary cutaneous IDCS have been reported. Histopathologically, IDCS presents as atypical spindle cells with irregular nuclei, and therefore can be difficult to distinguish from melanoma, follicular dendritic cell sarcoma, and Langerhans cell tumors by H&E examination alone. We report a unique case of a man with cutaneous IDCS that was initially misdiagnosed as melanoma. Having previously undergone an excision of a reported “melanoma” on the neck, he presented with a new growth on the cheek. Histopathologic findings revealed an atypical dermal lymphohistiocytic infiltrate around vessels and cells forming nests along the dermal‐epidermal junction. Immunohistochemical stains were strongly positive for S100, fascin, and lysozyme; on the other hand, CD1a, langerin, CD21, CD23, and SOX10 were negative. These immunohistochemical findings were consistent with IDCS, and the patient's prior biopsy specimen was then revisited. Similar staining revealed that lesion also to be a cutaneous IDCS. Follow‐up imaging with PET scan was negative for metastases, supporting the diagnosis of primary cutaneous IDCS. Our findings contribute to the limited literature on cutaneous IDCS and highlight a potential pitfall in its diagnosis because of overlapping histopathologic features with melanoma.