Sarcoidosis is chronic idiopathic multisystem granulomatous disease affecting lungs and mediastinal lymph nodes in more than 90% cases.¹ The pulmonary sarcoidosis usually presents with cough, dyspnoea and constitutional symptoms (unintentional weight loss, fatigue, night sweats).² About 30% of these patients may present with extrapulmonary manifestations.³ The isolated extrapulmonary sarcoidosis is seen only in less than 10% cases.⁴ Sarcoidosis affects middle aged patients and there is slight female predominance.⁵ Sarcoidosis can affect any organ including the visceral organs, skin, eye, heart, musculoskeletal system and nervous system; thus, imparting a heterogenous clinical presentation.^6,7

The etiology of sarcoidosis is still unclear. Environmental antigens can trigger granulomatous inflammation in genetically susceptible individuals.⁸ The diagnosis of sarcoidosis is based on exclusion of other possible causes, an explicable clinical presentation and presence of non-necrotizing granulomatous inflammation.⁹ The biochemical markers, calcium in serum and urine and angiotensin- converting enzyme (ACE) can be supportive in diagnosis and monitoring of sarcoidosis.¹⁰ Radiological imaging techniques, Positron emission tomography (PET- CT) and Magnetic resonance imaging (MRI) plays important role in diagnosis and evaluation of lesions in sarcoidosis.¹¹ The management of sarcoidosis depends on the clinical presentation and systems involved.¹² The mainstay of treatment is immunosuppressive therapy or biologic immunomodulatory medications.¹³ The objective of this systematic review was to study the clinicopathological spectrum of extrapulmonary sarcoidosis.

The study comprises an analysis of other studies that have reported the clinicopathological profile of extrapulmonary sarcoidosis. We searched for the related full text articles in English language published between 2019 to 2024 in PubMed database. The search term/ key words used to identify the articles relevant to the research topic included “extrapulmonary sarcoidosis” which yielded 133 results. The abstracts of the located articles were carefully assessed for the quality and appropriateness of subject by examining aim, study design, results, discussion and conclusions of each selected article. The number of studies found relevant to research title were 61. The studies which documented the following points were included for systematic review: (i) Age and sex of patient, (ii) Site of extrapulmonary sarcoidosis, (iii) Whether associated with pulmonary sarcoidosis or not, (iv) The onset of clinical symptoms and clinical presentation, (v) Relevant investigations for diagnosis, (vi) Specific treatment strategies, (vii) Patient outcomes. Keeping in view these criteria, 42 studies were included for quantitative synthesis. Figure1 shows a PRISMA (Preferred Reporting Items for Systematic review and Meta analysis) flow diagram depicting the overall procedure for the literature search to data retrieval. The data collection process involved summarizing the findings of selected studies by focussing on the age, sex, onset of symptoms, investigations done, site of extrapulmonary sarcoidosis and whether pulmonary sarcoidosis was evident or not.

Fig.1: The overall process of study selection depicted in the form of a PRISMA flow chart

A total of 42 studies were included in the systematic review. Table 1 gives an overview about the studies that were selected at the end of the search process. The final set of articles consisted of case reports.

Patient demographics, clinical manifestations and diagnosis:

Out of 42 cases, the average age was 46.31yrs (range: 4yrs- 78yrs) and the majority were males (57.1%) and male to female ratio was 4:3.  The majority of cases were seen between 51- 60 years (Fig2). The most common presenting complaints were, one or the other constitutional symptoms (fatigue, weakness, night sweats, unintentional weight loss) seen in 30 out of 42 cases. Other complaints were organ specific or were related to hypercalcemia (muscle cramps, frequent renal stones, increased thirst, headache, elevated blood pressure). One case presented with upper abdominal pain and vomiting due to hypercalcemia induced acute pancreatitis. One case presented with signs and symptoms related to diabetes insipidus due to involvement of pituitary gland. One case of splenic sarcoidosis presented with severe epistaxis. Multisystemic sarcoidosis was seen in 37 out of 42 cases. The five isolated cases of extrapulmonary sarcoidosis were two cases each of splenic and soft tissue sarcoidosis and one case of cardiac sarcoidosis. Table 2 shows the extrapulmonary site involved by sarcoidosis and the frequency of involvement found in this review. Out of 42 cases, the extrapulmonary site most frequently involved were lymph nodes (excluding mediastinal), hepatic and splenic seen in 18, 17 and 16 cases respectively. This was followed by cutaneous and subcutaneous sarcoidosis (10 cases). Bone marrow, musculoskeletal and ophthalmic involvement was seen in 6 cases each. Renal involvement was seen in 5 cases, cardiac in 4 cases and gastrointestinal tract in 3 cases. Two cases each of urogenital system and nervous system involvement were seen. One case each of pituitary gland and adrenal gland involvement was seen. Simultaneous pulmonary involvement was seen in 18 cases. Out of 42 cases, serum angiotensin converting enzyme (ACE) levels and serum calcium levels were documented in 33 and 31 cases respectively. ACE levels were found to be increased in 20 cases and calcium levels were increased in 17 cases, in upper normal range in 2 cases, within normal range in 11 cases and decreased in one case. ESR was raised in 10 out of 12 cases which documented its levels. CRP was commented upon in 9 cases and was found to be raised in 8 cases. In cases with multisystemic and hepatic sarcoidosis, liver function tests and renal function tests were deranged in 16 and 9 cases respectively. Also, 1, 25- dihydroxy Vitamin D3 levels were documented to be raised in 7 cases with multisystemic sarcoidosis. The cardiac sarcoidosis patients had abnormal ECG findings showing various conduction abnormalities. Four cases reported raised serum IL-2 receptor (sIL-2R). Increased levels of S. amylase, S. lipase was seen in one case with hypercalcemia induced pancreatitis.  One or more radiological investigations including Ultrasonography (USG), Computed Tomography (CT) scan, Magnetic resonance imaging (MRI), Fluorine -18 fluorodeoxyglucose positron emission tomography (18F- FDG- PET) scan were done in all 42 cases and histopathological examination was done in 41 cases. In 40 cases, non-caseating granulomas suggesting sarcoidosis were seen and one rare case of necrotizing sarcoid granulomatosis was also seen.

Fig.2: Age related distribution of cases of extrapulmonary sarcoidosis

Table 1: Studies selected at the end of the search process

PET FDG (Fluorodeoxyglucose positron emission tomography), Bx (Biopsy), NCG (Non- caseating granuloma), LFT (Liver function test), RFT (Renal function test), CT (Computed tomography), MRI (Magnetic resonance imaging), EBUS (Endobronchial ultrasound), MRCP (Magnetic resonance cholangiopancreatography)

Table 2: Sites of Extrapulmonary sarcoidosis

Sarcoidosis is a systemic disease of unknown etiology, characterized by presence of non-necrotizing granulomas in the involved tissues. Though most frequently affected tissue is the pulmonary interstitium, sarcoidosis can involve almost any organ/ tissue system.¹³ The clinical course may range from spontaneous remission, relapse and persistent disease activity.¹⁴ Extrapulmonary manifestations of sarcoidosis can be seen both in presence and absence of pulmonary disease. Isolated extrapulmonary sarcoidosis is a rare entity seen in less than 10% cases.¹⁵ In this review, pulmonary involvement was seen in approximately 43% cases who presented with a variety of complaints including non-specific constitutional symptoms to symptoms suggesting specific extrapulmonary disease. The pulmonary component of sarcoidosis became evident only through investigational work up. The disease mostly affects young to middle aged adults and female preponderance is seen.¹⁶ In this review, the mean age was 46.31 years and 57.1% cases were males. The clinical features and symptoms of sarcoidosis depend on the organs affected and patient may present with pulmonary and extrapulmonary manifestations.¹⁷ Most patients with sarcoidosis present with chest symptoms comprising cough, dyspnea, chest pain, constitutional symptoms and other complaints depending on the extent of disease and other organs affected by sarcoidosis.¹⁶ Sarcoidosis is a diagnosis of exclusion because of variable clinical presentation and multisystemic involvement. Depending on the organs involved and the clinical presentation, alternative causes of granulomatous disease, malignancy, metastatic disease and autoimmune disease must be ruled out. In this review, the patients mostly presented with constitutional symptoms (fatigue, weakness, night sweats, unintentional weight loss) and other complaints including back pain, pain abdomen, dyspnea, headache and fever.^13,15,18-45 These were seen in 30 out of 42 cases. Musculoskeletal sarcoidosis cases presented with generalized weakness, pain in extremities.^20,25,46 Soft tissue swelling/ progressively enlarging swelling was the presenting complaint in few cases.^47,48,49 Bony pains and constitutional symptoms were chief complaints in cases with bone marrow sarcoidosis.^{19,22,31,35,39,43} One case with neurological involvement presented with polyarthralgia and bilateral hearing loss along with constitutional symptoms.²⁷ The cardiac sarcoidosis patients had headache, dizziness, light-headedness, chest discomfort, near fall episodes/ intermittent episodes of transient loss of consciousness. ^28,29,45,50 One case was evaluated for hypercalcemia (found on routine laboratory investigations) and had complaints of constipation, muscle cramps and frequent renal stones. The patient had splenic and nodal sarcoidosis.⁵¹ Other case was also diagnosed with splenic and nodal sarcoidosis while being evaluated for high blood pressure.⁵² One case of multisystemic sarcoidosis presented with symptoms related to diabetes insipidus.⁵³ Two cases with testicular involvement presented with testicular pain (30) and painless mass scrotum.⁵⁴ Two of the three cases with ocular sarcoidosis presented with vision changes, redness, photophobia and blurring of vision.^30,55 A case of hepatic and gastrointestinal tract sarcoidosis had presented with chronic diarrhoea and abdominal distention.⁵⁶ Hypertensive emergency, acute renal failure and severe hypercalcemia were seen in a patient and absence of hilar lymphadenopathy on CT imaging made multiple myeloma a differential in this case.⁵⁷ One case of splenic sarcoidosis presented with severe epistaxis and laboratory investigation showed bicytopenia (anemia, thrombocytopenia) and raised reticulocyte count.⁴⁰ Splenic sarcoidosis poses diagnostic challenge, and the differential diagnosis include hematologic malignancies, primary or metastatic splenic tumors, inflammatory diseases, infectious conditions and infections.¹³

Thus, the heterogenous clinical presentation of extrapulmonary sarcoidosis makes the diagnosis of sarcoidosis challenging.¹⁸

Cutaneous manifestations of sarcoidosis may present at any stage of the disease but is more often seen at the onset.^58,59 Specific skin lesions may occur in 9% to 37% of patients. The lesions are lupus pernio (LP), infiltrated plaques, maculopapular eruptions, subcutaneous nodules and rare entities such as alopecia, ulcers, hypopigmented patches and ichthyosis.⁵⁹

Cutaneous and subcutaneous lesions in this review were seen in 10 out of 42 cases (23.8%).^{23,26,31,34,35,36,46,50,53,55} The lesions ranged from pruritic lesions, papular rashes, plaques and hardened palmer surface (calcinosis cutis). Diagnosis of extrapulmonary sarcoidosis with multisystem involvement can be quite challenging due to non-specific and heterogenous clinical presentation.⁶⁰ The radiological presentation can also mimic malignant pathology.⁶¹

So, to arrive at diagnosis of extrapulmonary sarcoidosis, other causes of granulomatous diseases including infections such as tuberculosis, histoplasmosis and systemic autoimmune diseases must be excluded. Also, malignant neoplasms such as lymphomas, multiple myelomas and metastatic tumors must be ruled out.²⁰

The malignant osseus lesions and osseus sarcoidosis have overlapping clinical and radiological features. Fluorodeoxyglucose positron emission tomography (FDG PET) scan in sarcoidosis also shows similar hypermetabolic lesions as seen in malignant conditions. FDG accumulates within the activated macrophages and epithelioid cells in active granulomatous inflammation.⁶² Therefore, the diagnosis of extrapulmonary sarcoidosis is highly dependent on a compatible clinical presentation and radiological findings. However, definitive diagnosis is only established with the cytological/ histological evidence of non-caseating granulomatous inflammation in the organ evaluated.⁶³

In the absence of pulmonary involvement, a diagnosis of sarcoidosis is made very cautiously. Extrapulmonary involvement occurs in 30% of cases of sarcoidosis and the most common sites are liver, spleen, biliary tree, peritoneum and lymph nodes.¹⁵ In this review also, the most common sites of extrapulmonary sarcoidosis were lymph nodes, liver and spleen.  Patients with hepatic sarcoidosis may present with non-specific symptoms such as fever, weight loss, anorexia, abdominal pain along with jaundice and itching.^46,63 In hepatic sarcoidosis, liver function test (LFT) abnormalities are common, whereas cirrhosis with ascites and portal hypertension are rare.⁶⁴ Deranged liver function test with elevated serum alkaline phosphatase is seen in 90% of patients and serum transaminases are elevated in 50- 70% of patients but less severely elevated than alkaline phosphatase.¹⁵ In this review, deranged LFT was found in 15 out of 17 hepatic sarcoidosis cases. Two cases with multisystemic involvement (without apparent hepatic involvement) also documented deranged LFT and serum alkaline phosphatase was particularly elevated. Patients with splenic sarcoidosis may present with constitutional symptoms and left upper quadrant abdominal pain.^63,65 Massive splenomegaly is the most common presentation followed by multiple splenic lesions. Isolated splenic sarcoidosis is extremely rare and is difficult to diagnose and needs exclusion of various conditions including hematolymphoid malignancies, primary or metastatic tumors, infiltrative diseases, inflammatory conditions and various infections.¹³ Hematologic abnormalities in sarcoidosis may be secondary to hypersplenism, bone marrow suppression or due to autoimmune mechanisms.⁶⁶ In this review, hematologic abnormalities were seen in splenic sarcoidosis in the form of thrombocytopenia¹³, bicytopenia⁴⁰ and pancytopenia.^39,52

Bone marrow sarcoidosis may present with cytopenias, lymphadenopathy and hypersplenism. The occurrence of granulomas in bone marrow biopsies has been estimated to be low, ranging from 0.3 to 2.2% in various studies. Sarcoidosis account for a significant proportion of these cases and as per a retrospective review by Brackers et al⁶⁷, the bone marrow sarcoidosis was as high as 21%. There could be a possibility that bone marrow involvement is more common than reported as most patients do not undergo a bone marrow biopsy.³⁹ James et al⁶⁸ reported that bone marrow involvement occurred more frequently in those with non-pulmonary sarcoidosis (12.1%) compared to those with pulmonary sarcoidosis (6%). In this review, 6 out of 42 cases had bone marrow sarcoidosis. Out of these 6 cases, 5 did not have evidence of pulmonary sarcoidosis. Renal involvement may be seen in up to 0.7% patients with sarcoidosis.³⁶ Renal involvement in sarcoidosis may be represented by specific histological changes or by abnormal calcium metabolism, nephrolithiasis and nephrocalcinosis. The renal manifestations in sarcoidosis are marked by hypercalcemia, hypercalciuria, nephrolithiasis, nephrocalcinosis, granulomatous or non-granulomatous interstitial nephritis, glomerular and tubular disease and ureteral obstruction. Hypercalcemic nephropathy is the main cause that leads to end stage renal disease (ESRD) in renal sarcoidosis.³⁸

Hypercalcemia results from increased PTH independent conversion of 25 hydroxyvitamin D to 1,25- dihydroxy vitamin D by 1- alpha hydroxylase expressed by activated macrophages within granulomas.³³ This leads to subsequent increase in activated vitamin D causing increased calcium absorption from intestines and resorption from bones.⁵⁷ Hypercalcemia can have a variety of clinical manifestations including constipation, nausea, vomiting, dysrhythmias, dehydration, polyuria, nephrolithiasis, acute renal injury, weakness, muscle pain, behavioural changes, anxiety and various other neurological abnormalities.⁶⁹ Hypercalcemia through various mechanisms can also give rise to pancreatitis. Elevated calcium levels may lead to premature activation of pancreatic enzymes within the acinar cells, resulting in autodigestion and inflammation of pancreatic tissue. Also, hypercalcemia impairs microcirculatory flow in the pancreas leading to ischemia and further tissue damage.³³ Serum calcium levels were frankly elevated in 17 cases and in 2 cases, were in the upper normal ranges. The hypercalcemic patients presented with either symptoms related to hypercalcemia or were found to have elevated serum calcium levels during evaluation. Neurosarcoidosis (NS) occurs in 3- 20 % of patients with systemic sarcoidosis and may involve the cranial nerves, meninges, brain parenchyma, spinal cord, peripheral nerves and muscles.⁵³ Cranial nerves II, VII and VIII are the most affected.²⁷ The major challenge in diagnosing NS is the difficulty of obtaining neural tissue for histologic evaluation. NS is typically assumed when a patient has clinical evidence of central or peripheral nervous system inflammation consistent with NS and pathologic proof of sarcoidosis in another organ system.⁷⁰ The endocrine signs of sarcoidosis include diabetes insipidus (DI), hypothalamic hypopituitarism, amenorrhea- galactorrhea, hypogonadotropic hypogonadism, secondary hypothyroidism, and diffuse goitre or a solitary thyroid nodule.⁵³ Cardiac involvement is found in 5% cases of sarcoidosis.²⁸ The clinical manifestations of cardiac involvement are highly variable, and patient may present with conduction abnormalities, arrythmias, and heart failure. Occasionally, cardiac sarcoidosis may be the only manifestation of sarcoidosis, and it should be suspected in young patients presenting with conduction abnormalities of unknown etiology.⁷¹ Patient may show non-specific ECG findings, conduction abnormalities, ventricular arrhythmias, first degree AV block, prolonged QT corrected for heart (QTc) interval.²⁸ Cardiac sarcoidosis may be diagnosed by direct biopsy. However, it is invasive and has low sensitivity due to patchy involvement of heart in sarcoidosis. Recently, cardiac magnetic resonance (CMR) and PET with FDG have replaced endomyocardial biopsy²⁹. Testicular sarcoidosis is rare and is frequently underdiagnosed as its incidence is reported as high as 5% at autopsy by various studies.^72,73 In this review, two studies highlighted the involvement of genitourinary system by sarcoidosis. The patient may have non-specific clinical manifestations and varied symptoms including sharp pain scrotal region, lower abdominal pain, dysuria, progressively increasing mass in scrotum.^30,54 Scrotal mass can be due to variety of diseases including hernia, tuberculosis, syphilis, abscess, malignant tumors. Sarcoidosis is a diagnosis of exclusion.^74,75. Skopelidou et al⁵⁴ highlighted a case of unnecessary orchidectomy due to atypical sarcoidosis manifesting as unilateral scrotal mass. The orchidectomy specimen on histopathological examination showed non caseating epithelioid cell granulomas with multinucleated giant cells showing asteroid inclusions. Following orchidectomy, a full body CT scan revealed extensive lymphadenopathy and focal involvement of lung parenchyma. This case underlines the importance of chest examination using imaging methods and the histopathological confirmation of the diagnosis in such cases. Ocular involvement may be the initial manifestation of sarcoidosis and anterior uveitis is the most common presentation. The uveitis is characteristically granulomatous with medium to large sized, mutton fat keratic precipitates. Other ocular manifestations include dacryoadenitis, conjunctival nodules, scleritis, episcleritis, non-specific conjunctivitis, interstitial keratitis, intermediate uveitis, posterior uveitis and optic neuritis.⁵⁵ In sarcoidosis involving gastrointestinal tract, the inflammatory damage may lead to luminal narrowing, dysmotility or ulceration. Gastrointestinal sarcoidosis may flare up in patients with asymptomatic pulmonary disease.²²

Due to heterogeneity, complexity and multisystemic involvement in sarcoidosis, there is no ideal pathognomonic biomarker to confirm the diagnosis of sarcoidosis. Serological biomarkers such as serum angiotensin converting enzyme (ACE), soluble IL- 2R, chitotriosidase, lysozymes, serum amyloid A protein have been examined for potential roles in diagnosing or monitoring disease activity.⁷⁶ Serum ACE, produced by the epithelioid cells of the sarcoid granuloma is presently the most well-known biomarker.³¹ Serum ACE levels are elevated in 75% of untreated cases of sarcoidosis. However, its diagnostic utility is limited due to poor sensitivity and specificity.²² Serum soluble IL-2R has been suggested as a useful marker for identifying extrapulmonary involvement in sarcoidosis patients.⁷⁶ Radiological imaging plays an important role in diagnosing extrapulmonary sarcoidosis. Computed Tomography (CT) scan, Magnetic resonance imaging (MRI), Fluorine -18 fluorodeoxyglucose positron emission tomography (18F- FDG- PET) are indispensable in the assessment of lesions in various organs affected by extrapulmonary sarcoidosis.²⁶

Extrapulmonary sarcoidosis has diverse clinicopathological manifestations due to atypical presentations and multisystemic involvement. Careful evaluation of clinical symptoms combined with serum biomarkers and other laboratory investigations, radiological findings and histopathological examination is necessary to rule out other infectious, inflammatory and neoplastic conditions that mimic sarcoidosis. Thus, because of the heterogenous clinical manifestations and disease course, a systematic multidisciplinary approach is needed for early diagnosis and treatment of sarcoidosis. This systematic review provides a spectrum of clinicopathological manifestations of extrapulmonary sarcoidosis with some interesting and rare case scenarios highlighting the complex nature of this disease. Thus, clinicians must exercise caution and high index of suspicion for timely diagnosis, effective treatment of sarcoidosis and for avoidance of complications due to missed or delayed diagnosis.

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