Perrin Christophe
Laboratoire Central d'Anatomie Pathologique, Hôpital L. Pasteur, University of Nice, France; and.
Nail Dermatology Consultations, Cannes, France.
Am J Dermatopathol. 2023 Jan 1;45(1):40-46. doi: 10.1097/DAD.0000000000002328. Epub 2022 Dec 7.
The concept of nail psoriasis as an entheseal-driven disease has essentially been formulated on the basis of radiological findings because it is usually not possible to obtain the tissue directly from the joints. The aim of this retrospective study was to evaluate the histological features of isolated nail psoriasis with and without distal interphalangeal psoriatic arthritis (PsA), focusing on the question as to whether the fascia and adipose tissue surrounding the apex of the nail unit genuinely show an inflammatory infiltrate. In support of the nail-enthesitis theory, an ongoing inflammatory infiltrate could be expected. An immunohistochemical study was performed to evaluate the distribution and phenotype of the inflammatory infiltrate in nail psoriasis with and without PsA. This study did not show an inflammatory infiltrate in the fascia connecting the nail to the extensor tendon. CD8 and CD4 subsets were present in equal number in the nail dermis of nail psoriasis with or without PsA, which is a similar distribution to that seen in psoriatic synovium while skin psoriasis is characterized by a dermal predominance of CD4 T lymphocytes. Because of this study and recent microanatomic studies of the normal nail unit, it is possible to move away from a purely anatomic explanation of the strong association between nail psoriasis and PsA and to propose immunological factors as contributory. This study provides support for the hypothesis that CD8+ T cells play a crucial role in the pathogenesis of nail psoriasis through a pathogenic pathway similar to that of PsA and contrasting with that of the skin.
指甲银屑病作为一种附着点驱动性疾病的概念，基本上是基于放射学研究结果而形成的，因为通常无法直接从关节获取组织。这项回顾性研究的目的是评估孤立性指甲银屑病伴或不伴远端指间关节银屑病关节炎（PsA）的组织学特征，重点关注指甲单元顶端周围的筋膜和脂肪组织是否真的出现炎性浸润这一问题。支持指甲附着点炎理论的话，预计会存在持续性炎性浸润。进行了一项免疫组织化学研究，以评估伴或不伴PsA的指甲银屑病中炎性浸润的分布和表型。这项研究未显示连接指甲与伸肌腱的筋膜中有炎性浸润。在伴或不伴PsA的指甲银屑病的甲真皮中，CD8和CD4亚群数量相等，这与银屑病滑膜中的分布相似，而皮肤银屑病的特征是真皮中CD4 T淋巴细胞占优势。由于这项研究以及最近对正常指甲单元的微观解剖学研究，有可能不再单纯从解剖学角度解释指甲银屑病与PsA之间的强关联，并提出免疫因素也起作用。这项研究支持了以下假设：CD8 + T细胞通过与PsA相似且与皮肤不同的致病途径，在指甲银屑病的发病机制中起关键作用。
