Sarcoidosis, granulomas and myopathy syndromes: A clinical-pathology review

Neuropsychiatric manifestations of sarcoidosis

BACKGROUND

There has been significant progress in understanding neurosarcoidosis (NS) as a distinct disorder, which encompasses a heterogeneous group of clinical and radiological alterations which can affect patients with systemic sarcoidosis or manifest isolated.

RATIONALE AND AIM OF THE STUDY

The healthcare challenges posed by NS and sarcoidosis in general extend beyond their physical symptoms and can include a variety of psychosocial factors, therefore the recognition of main neuropsychiatric symptoms can be useful to approach patients with NS. Methods: For this purpose, databases such as Pubmed, Medline and Pubmed Central (PMC) have been searched.

RESULTS

A correct diagnosis of NS is established by the combination of clinical picture, imaging features and the histopathological finding of non-caseating and non-necrotizing granulomas. After analyzing the current literature, there is a need for specific, case-control, cohort and clinical trials on the psychiatric manifestations of sarcoidosis, because the evaluation of psychological distress (in terms of emotional suffering e.g. anxiety or depression) is often underestimated.

DISCUSSION AND CONCLUSION

Exploring the neuropsychiatric manifestations of sarcoidosis is useful to raise awareness of this condition among clinicians and to establish a holistic management, which includes both physical and psychological aspects.

Rheumatic Manifestations of Sarcoidosis

Sarcoidosis is a multisystem granulomatous inflammatory disorder, of unknown aetiology, which causes a wide spectrum of clinical phenotypes. It can present at any age, most commonly between 20 and 60 years, with a roughly equal sex distribution. Diagnosis is often delayed due to multiple diagnostic mimics, particularly joint disease. Common presenting features include pulmonary disease, with bilateral hilar lymphadenopathy and pulmonary infiltrates, cutaneous lesions, and ocular disease. Musculoskeletal manifestations are reported in 10-40% of patients with sarcoidosis and include bone lesions, acute arthritis, chronic arthritis, axial disease, dactylitis, and sarcoid myopathy, which are explored in detail in this review article. Diagnosis is confirmed through histological evidence of non-caseating granuloma on tissue biopsy. Newer imaging modalities, including 18FFDG PET/CT, can help identify the extent of musculoskeletal involvement, and biomarkers can provide weight to a diagnosis, but there is no single biomarker with prognostic value for disease monitoring. The mainstay of treatment remains corticosteroids, followed by disease-modifying antirheumatic drugs such as methotrexate and antimalarials. More recently, biologic treatments have been used successfully in the treatment of sarcoidosis with rheumatic involvement.

Neurosarcoidosis

Sarcoidosis affects the nervous system in 5% of cases. 60% of cases involve the cranial and peripheral nerves, the remainder the central nervous system, in which a leptomeningitis, a pachymeningitis and a vasculitis may arise. Stroke and cerebral haemorrhage may occur, and certain infections in the brain are more likely with sarcoidosis. Patients respond well to treatment but oftentimes with residual neurological impairments which may be severe. A greater understanding of the disease and the need for early treatment and use of biological therapies have improved treatment outcome in recent times.

Spatial Transcriptomics Reveals Signatures of Histopathological Changes in Muscular Sarcoidosis

Sarcoidosis is a multisystemic disease characterized by non-caseating granuloma infiltrating various organs. The form with symptomatic muscular involvement is called muscular sarcoidosis. The impact of immune cells composing the granuloma on the skeletal muscle is misunderstood. Here, we investigated the granuloma-skeletal muscle interactions through spatial transcriptomics on two patients affected by muscular sarcoidosis. Five major transcriptomic clusters corresponding to perigranuloma, granuloma, and three successive muscle tissue areas (proximal, intermediate, and distal) around the granuloma were identified. Analyses revealed upregulated pathways in the granuloma corresponding to the activation of T-lymphocytes and monocytes/macrophages cytokines, the upregulation of extracellular matrix signatures, and the induction of the TGF-β signaling in the perigranuloma. A comparison between the proximal and distal muscles to the granuloma revealed an inverse correlation between the distance to the granuloma and the upregulation of cellular response to interferon-γ/α, TNF-α, IL-1,4,6, fibroblast proliferation, epithelial to mesenchymal cell transition, and the downregulation of muscle gene expression. These data shed light on the intercommunications between granulomas and the muscle tissue and provide pathophysiological mechanisms by showing that granuloma immune cells have a direct impact on proximal muscle tissue by promoting its progressive replacement by fibrosis via the expression of pro-inflammatory and profibrosing signatures. These data could possibly explain the evolution towards a state of disability for some patients.