Line-field confocal optical coherence tomography, optical coherence tomography and reflectance confocal microscopy in a case of cutaneous sarcoidosis.

Abstract

Chronic sarcoidosis is a rare granulomatous multisystem disease and may be life threatening when lung-involvement is present. Cutaneous sarcoidosis (CS) manifests in up to 35% of the cases and may be an apparent indicator to early diagnosis.1, 2 It is crucial to distinguish between unspecific CS lesions, related to granulomatous inflammation, and specific ones, related to granuloma infiltration of the skin.1 Usually, skin findings of CS are multiform and may imitate other skin diseases.3-5 Hence, histology is the gold standard to detect sarcoidal noncaseating granulomas, conglomerates of epithelioid histiocytes, giant cells and macrophages. While for diagnosis of ocular sarcoidosis, optical coherence tomography (OCT) is used for visualization of inflammation, OCT is not routinely used in the diagnosis of CS.6 Only two case reports on CS using reflectance confocal microscopy (RCM) exist.7, 8 Line-field confocal OCT (LC-OCT) is a further development of OCT, allowing visualization of epidermal and dermal (non-)pigmented structures at cellular resolution, using en-coupe/en-face and 3D imaging modalities.9 On the upper left back of a 78-year-old woman, a large brownish plaque was noticed (Figure 1a). Red-to-purple plaques and nodules on the nose, nasolabial folds and on both cheeks were retrospectively identified as lupus pernio (Figure 1b). The lesion on the back was examined using dermoscopy, OCT (VivoSight Dx®, Michelson Diagnostics Ltd), LC-OCT (deepLive™®, DAMAE Medical) and RCM (VivaScope® 1500, MAVIG GmbH). Polarized contact dermoscopy revealed multiple linear and branching vessels, yellowish-orange globular and leaf-like structures with depigmented scar-like areas. The background had a whitish atrophic appearance with multiple fine branching vessels (Figure 1c). In 3D-LC-OCT subepidermal hyporeflective ovoid formations, embedded into hyperreflective connective tissue, were observed (Figure 2a). OCT provided an overview by depicting multiple dark nodules due to a deeper penetration depth, revealing dermal hypervascularization (Figure 2c). Using RCM, hyporeflective ovoid nodular structures, increased surrounding vascularization and inflammatory infiltrates were visualized in the papillary dermis (Figure 2d). In en-face-LC-OCT and RCM bright beaded-like structures and enlarged hyperreflective cells within each individual nodule surrounded by a bright stroma and accompanied by smaller hyperreflective cells were seen (Figure 2b,d). From the specific site where dark nodules were found, punch biopsy was taken and sarcoidal non-necrotizing granulomas were confirmed histologically (Figure 1d). In correspondence to histology, RCM and (LC-)OCT were able to identify hyporeflective round-to-ovoid subepidermal structures as granulomas. The surrounding bright stroma corresponded well with concentric fibrosis. Using LC-OCT, the cellular resolution allowed the possible identification of smaller hyperreflective cells as lymphocytes and enlarged hyperreflective cells within the granuloma as possible giant cells (Figure 2a,b), whereas OCT cannot visualize cellular structures due to its lower resolution. Necrotizing granulomas would look different showing a dark centre. Since CS is a masquerader in dermatology, we were encouraged to see that subepidermal granuloma, the groundbreaking feature in histology, can be visualized using RCM and (LC-)OCT. By dermoscopy only, the identification of CS might be challenging since diverse variants are described.3-5 When diagnosis of CS is considered, RCM and (LC-)OCT may provide a feasible and noninvasive approach for lesion imaging and may help to narrow the diagnosis of CS. Especially in cases where the skin region of interest is vulnerable to punch biopsy, noninvasive imaging may allow identification of subepidermal granuloma and to obtain a more significant histological result, when the region of interest is imaged and identified prior to biopsy. This might be significant, since in 80% cases, CS develops before or at the time of diagnosis of the systemic form.10 Detection of subepidermal elliptic dark structures using (LC-)OCT and RCM, corresponding to granulomas in histology, may help to guide the diagnosis of CS eventually. This article has no funding source. None. The patient in this manuscript has given written informed consent to the publication of her case details.