Scripties UMCG - Rijksuniversiteit Groningen
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Ashy Dermatose - de histopathologische inter-observer correlatie

(2016) Berghuis, M. (Marieke)

Background and objectives Ashy Dermatosis (AD) is a rare pigment disorder clinically characterized by ‘ash –gray’ discoloration of the skin. It is an acquired slowly progressive, persistent skin disease of unknown etiology. There is no well proven effective treatment. It is cosmetically very disturbing for patients. The aim of this study is to clarify the histopathology of AD, because in that part little research has been done. We want to investigate if we can identify a clear histopathological pattern by an inter-observer correlation analysis.
Material and methods Three dermatologists and one pathologist, all specialized in dermatopathology and/or pigment disorders, reviewed 54 skin biopsies from patients who were previously diagnosed with AD. The observers scored histopathological characteristics and gave the most suspect diagnosis. The location of biopsy was reported only, the clinical symptoms and differential diagnosis were not mentioned. The inter-observer correlation is measured by pair-wise similarities and multirater Fleiss' Kappa.
Results 81.5% of the included patients were female. Skin type IV and V were most common. The ages ranged between 16 and 73 years. The Fleiss' kappa for diagnosis was 0.18 which can be interpreted as a ‘slight’ correlation. In many biopsies other diagnoses seemed more likely than AD. The percentage of pairwise similarities for assessing characteristics was between 61 and 96 % with kappa values between -0.01 and 0.41 (bad to reasonable agreements) except for 'subepidermal fibrosis’ (35% pairwise agreement and κ = -0.33). In only four cases they all agreed AD as the pathology conclusion. They scored respectively 28, 27, 14 and 28 times AD as diagnosis. The characteristics of these cases were displayed graphically per observer. The average AD case had pigment-incontinence, superficial lymfohistiocytair perivascular infiltrate and mild vacuolization of the basal cell layer. Epidermal atrophy, hyperkeratosis and exocytosis of lymphocytes could be quite possible. The presence of civatte bodies differed per observer.
Conclusion It appears that there was no unilateral agreement of histopathological pattern for AD according to the observers. They often set other criteria and pointed different biopies as AD. But they also differ in scoring histological characteristics, which is an interesting finding for histopathological diagnosing in general. The absence of clinic and differential diagnosis is apparently important for a proper diagnosis of this skin disorder. A clear criterium for histopathology is necessary in future. It seems to be a ‘diagnosis per exclusionem’ right now. When it has anamnestic no triggers, it persists, is resistant for treatment and pathology seems not only conform but also closes out other disease, it can be diagnosed as AD.

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