Lymph nodes in the lungs are enlarged at least in some time in almost every sarcoidosis patient's journey, therefore pulmonologists are the most frequent referral targets for cases of suspected sarcoidosis. Pulmonologists know sarcoidosis as a benign disease based on the knowledge that only a fraction of patients require treatment because of their lung situation and many cases will resolve spontaneously without or despite intervention.

In practice, the situation is not that easy, because sarcoidosis is a systemic disease and extrapulmonary involvement is the reason for therapy in many cases. The range of symptoms sarcoidosis can generate is wide [16] and makes assignment tricky. Almost every patient's complains can be caused by sarcoidosis and it's hard to distinguish, because the situation of a patient can evolve over time, especially in a long-lasting course. Then the task of the discrimination of differential diagnoses is not only a case at first diagnoses, but an ongoing process.

During the journey of a patient there might come up concomitant diseases which will fit in the concept of comorbidities due to sarcoidosis or its treatment as the main disease requiring the sarcoidosis doctor to become a care coordinating hub because of the need of coordinated re-evaluation and therapy.

But patients are not always suffering just from sarcoidosis and its therapy alone, especially if they run into a chronic condition. Patients have symptoms and need care, regardless of the name of the underlying disease. A sarcoidosis doctor of a patient with ongoing complains usually spends ongoing a lot of time and effort assessing the patients situation, because sarcoidosis can generate close to every symptom in almost any part of the body [17]. In the process of the exclusion of differential diagnoses there might come up comorbidities with suspected origin in the main disease sarcoidosis or more or less completely different main maladies in the concept of multimorbidity [8].
For the patient, the distinction co- versus multimorbidity is usually a don't care situation. There is simply the need for someone who cares, who coordinates care in a multidisciplinary setting - for the benefit of the patient and its carers [2].

Early recognition and adequate treatment of co- or multi-morbidities is essential and has great potential to improve outcomes in patients with ILD [12].

In Sarcoidosis immune-mediated diseases are frequent and the discussion on overlapping syndromes is long-lasting [1]. Most frequent consistently reported diseases are systemic lupus erythematosus, autoimmune chronic hepatitis, multiple sclerosis, celiac disease, ulcerative colitis, Graves’ disease, and autoimmune thyroid disease [5, 11]. Numbers from different studies might inhibit a lot of bias from various reasons, especially if data are pooled from patients from different locations [15]. Nevertheless, there is credible evidence for correlations.

While thyroid function control should be established standard in patients care because of their frequent fatigue complains [10, 13], celiac disease (CD) is not often mentioned in sarcoidosis records, despite it can generate many symptoms also seen in sarcoidosis and has a similar list of concomitant morbidities [7]. In sarcoidosis patients, the relative risk for CD is found to be 4 times higher - and vice versa [3]. Hwang et al found even 10 sarcoidosis patients in their group of 866 CD patients [4].
While it doesn't sound efficient to screen for sarcoidosis in a CD patient group, considering CD in sarcoidosis patients might be beneficial because of the selection bias. Going with a prevalence for CD of 1:120 in Central Europe and an increased risk factor of 4, on average every 30th sarcoidosis patient would also suffer from CD. A recent study from Parma found gastrointestinal comorbidities in 3 out of 4 patients [14] which makes consideration of CD obvious, especially because of the availability of a very specific and sensitive blood test and a dietary "cure".

The discussion and the request to consider the association between sarcoidosis and CD is not new [6, 9] but needs ongoing remainders. The knowledge of the spectrum and number of concomitant maladies in the own patient group should be mandatory and should be known as indicator of good clinical care.

Summary

Coexistence of concomitant, often immune-mediated diseases in sarcoidosis is well known since quite some time. Nevertheless, reported prevalences are not really consistent for some reasons. Increased attention of the sarcoidosis care team could hold the potential to improve outcomes in patients, whereas comparable numbers could also serve as indicator for quality of service in patient management.

[1] D. Geraint James and O.P. Sharma: Overlap syndromes with sarcoidosis, Postgraduate Medical Journal (1985) 61, 769 - 771
Sarcoidosis has been observed in association with various autoimmune disorders, primary biliary cirrhosis, Crohn's regional enteritis, coeliac disease, amyloidosis and lymphoma, ...

[2] M. Drent: Sarcoidosis: benefits of a multidisciplinary approach (Abstract), Int Med (2003), 14, 217 - 220
Patients and also specialists from all participating medical disciplines — including respiratory diseases — may benefit from a multidisciplinary approach.

[3] Jonas F Ludvigsson, Jan Wahlstrom, Johan Grunewald, Anders Ekbom, Scott M Montgomery: Coeliac disease and risk of sarcoidosis (Abstract), Sarcoidosis Vasc Diffuse Lung Dis (2007) 24, 121 - 126
4 fold risk in Sweden.

[4] Elizabeth Hwang, Russell McBride, Alfred I. Neugut, Peter H. R. Green: Sarcoidosis in Patients with Celiac Disease, Dig Dis Sci (2008) 53, 977 – 981
... studies examining the relationship between celiac disease and sarcoidosis have been inconsistent.

[5] N Rajoriya, C J Wotton, D G R Yeates, S P L Travis, M J Goldacre: Immune-mediated and chronic inflammatory disease in people with sarcoidosis: disease associations in a large UK database (Abstract), Postgrad Med J (2009), 85, 233 - 237
Large UK epidemiologic observational study about association of sarcoidosis and inflammatory autoimmune diseases.
In the database with 600.000 persons there were 1.510 with the diagnosis sarcoidosis. Some maladies were more frequent seen in sarcoidosis patients than expected from controls (OR): SLE (OR 8.3), autoimmune chronic hepatitis (OR 6.7), MS (OR 3.3), coeliac disease (OR 3.1), ...

[6] Cristina D’Ercole, Angelo Zullo, Maria Consiglia Bragazzi & Salvatore Maria Antonio Campo: Letter Sarcoidosis and coeliac disease: do not forget the association!, Internal and Emergency Medicine (2012) 7
Sarcoidosis is about 4 times more frequent in patients with celiac disease and vice versa.

[7] Eugenia Lauret and Luis Rodrigo: Celiac Disease and Autoimmune-Associated Conditions, BioMed Res Int (2013), Article ID 127589
List of concomitant autoimmune diseases.

[8] Patompong Ungprasert, Eric L. Matteson, and Cynthia S. Crowson: Increased Risk of Multimorbidity Among Patients With Sarcoidosis: A Population-Based Cohort Study 1976 – 2013, Majo Clin Proc (2017) 92, 1791 - 1799 (web version)
Numbers hard(ly) to interpret, nevertheless clear increased disease-dependent risk for other conditions.
With a nice discussion of comorbid versus multimorbid.

[9] Letter to the Editor: Dalvir Gill, Kamalpreet Mann, Mitchell Lyons, Vanessa Goyes Ruiz, Ryan Dean, Pardeep Masuta, Jaswinder Virk, Zabeer Bhatti, Fatme Allam: Screening of Celiac Disease in Patients With Sarcoidosis?, The American Journal of Medicine (2017) 130
... early screening should be done in patients with sarcoidosis.

[10] Elizabeth Hwang, Russell McBride, Alfred I. Neugut, Peter H. R. Green: Sarcoidosis and Thyroid Autoimmunity, Frontiers in Endocrinology (2017) 8, Article 177
... higher risk for subclinical and clinical hypothyroidism, antithyroid autoantibodies, and in general, thyroid autoimmunity, ... in patients with sarcoidosis.

[11] Michelle Terwiel, Jan C Grutters, Coline HM van Moorsel: Clustering of immune-mediated diseases in sarcoidosis, Curr Opin Pulm Med (2019), 25, 539 - 553, DOI: 10.1097/MCP.0000000000000598
Clustering of sarcoidosis and other immune-mediated diseases in patients and in their relatives occurs for sarcoidosis, MS, celiac disease, Graves’ disease, and ulcerative colitis.

[12] Thesis Karen Moor: Innovative Approaches to Patient-centered Care and Research in Interstitial Lung Disease, Erasmus Universität Rotterdam (2020)

[13] Muhunthan Thillai, Christopher P Atkins, Anjali Crawshaw, Simon P Hart, Ling-Pei Ho, Vasileios Kouranos, Karen Patterson, Nicholas J Screaton, Joanna Whight, Athol U Wells: BTS Clinical Statement on pulmonary sarcoidosis, Thorax (2020). See BTS site link to some comments on Respiratory Futures
Simply Great.

[14] Ilaria Aredano, Barbara Burgazzi, Elena Beneventi, Matteo Goldoni, Veronica Alfieri, Marina Aiello, Fabio Agusta, Giuseppina Bertorelli, Alfredo Antonio Chetta: Comorbidities in sarcoidosis: a retrospective Italian study, ERJ Poster (2020) 56, suppl. 64
Comorbidities: cardiovascular 76%, gastroenterological 74%.

[15] P. Brito-Zerón, R. Pérez-Alvarez, C. Feijoo-Massó et al.: Coexistence of immune-mediated diseases in sarcoidosis. Frequency and clinical significance in 1737 patients, Joint Bone Spine (2021) 88, 105236
Every 6th sarcoidosis patient with an concomitant immune-mediated disease (OR 1.64).

[16] Marjolein Drent, Ulrich Costabel, Elliott D. Crouser, Johan Grunewald, and Francesco Bonella: Misconceptions regarding symptoms of sarcoidosis (Abstract), Lancet Respir Med (2021), DOI: doi.org/10.1016/S2213-2600(21)00311-8
Comment on the term parasarcoidosis which should be avoided, because all itemized symptoms are sarcoidosis. Great list of sarcoidosis-symptoms in the abstract data box.

[17] Dominique Valeyre, Florence Jeny, Cécile Rotenberg, Diane Bouvry, Yurdagül Uzunhan, Pascal Sève, Hilario Nunes, Jean-François Bernaudin: How to Tackle the Diagnosis and Treatment in the Diverse Scenarios of Extrapulmonary Sarcoidosis, Adv Ther (2021): DOI: 10.1007/s12325-021-01832-5
Best paper in 2021 on extrapulmonary sarcoidosis problems and therapy.

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Additional Literature

Xin Qiao, Shan He, Abdullah Altawil, Qiu-yue Wang, Jian Kang, Wen-yang Li and Yan Yin: Multisystemic Sarcoidosis presenting with Leg Ulcers, Pancytopenia, and Polyserositis was successfully treated with Glucocorticoids: A Case Report and Literature Review, Frontiers in Medicine (2022), DOI: 10.3389/fmed.2021.803852
Many symptoms aside the lungs.

J. Freire Carvalho: Letter to the Editor: Sarcoidosis associated with celiac disease: a unique clinical combination, EurRevMedPharmacolSci (2022), DOI: 10.26355/eurrev_202204_28449