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Sarcoidosis is a chronic disease of unknown origin that is characterized by the formation of noncaseating granulomas in the affected organs, predominantly in the lungs and the intra thoracic lymph nodes. Inflammation is mediated by lymphocytes of Th1 phenotype that lead to formation of non-caseating granulomas. The granulomas are the pathologic hallmark of the disease that usually occur in the bronchial sub mucosa [1,2]. Prognosis is excellent with a spontaneous resolution in 85% of the stage I patients. Advanced pulmonary disease develops in approximately 5% of the sarcoidosis patients causing death in less than one percent by lung fibrosis [3,4]. Chronic pulmonary disease usually develops over one or two decades. Prognostic factors for persistent pulmonary disease become evident within two years following diagnosis [5,6].
Currently, there are no specific benchmarks to predict the development of persistent pulmonary sarcoidosis. Although sarcoidosis may show a progressive course with relapse and remissions, it does not always lead to end stage pulmonary fibrosis . The mechanisms for the variable course and outcome of sarcoidosis are unknown. The granuloma burden in sarcoidosis appears to be the hallmark of persistent and progressive disease. The kinetics of granuloma formation is variable between individual patients  as well as the dynamics of different organ involvement in the same patient. Treatment of sarcoidosis depends on the supression of granuloma formation and stabilization of organ function. Although numerous risk factors like lupus pernio, cystic bone lesions, hypercalcemia, and multiple organ involvement have been defined for advanced pulmonary sarcoidosis, no study has precisely established the clinical markers for persistent disease. This may be associated with the fact that outcome of sarcoidosis is dependent on many factors including genetic, hormonal, and environmental effects.
Identification of patients with a potential risk factor for advanced disease is the most crucial point in the follow-up of sarcoidosis patients. In this review, the aim is to discuss the potential prognostic factors that play a role in lung fibrosis and in other unfavorable outcomes of sarcoidosis. Since the disease shows a variable course with relapses and remissions, the most critical endpoint for clinicians is to diagnose patients that may show a chronic course resulting with end-stage pulmonary fibrosis and commit early treatment to suppress granuloma formation leading to organ dysfunction.
Monitoring disease severity is the fundamental point for clinical management of sarcoidosis patients. Previously, pulmonary function trends and chest radiology have been the benchmark for patient follow-up and prognostic evaluation. Serial pulmonary function and radiologic evaluation are not sensitive markers to identify patients with a severe prognosis. The heterogeneity of pulmonary function tests in sarcoidosis is well known. Lung function impairment is usually greater in severe parenchymal disease, especially in patients with stage III and IV while the same pulmonary function pattern may be observed in earlier stages of the disease. A restrictive pattern is observed in approximately 30-50% of the patients and a significant obstructive functional impairment may also be present [7,9-11].
Initial lung function may be useful for prognostic evaluation of sarcoidosis. Viscum has reported that patients with a FEV1 less than 50% of predicted had an increased mortality risk of 4.2 compared to patients with normal function. Bronchial obstruction was also associated with an increased mortality risk . Mana et al.  have shown that low initial FVC may a predictor of chronic sarcoidosis . In contrast to unfavorable prognostic value of initial lung function, Judson has shown that majority of the patients had stable FVC and FEV1 after two years . A decreased DLCO may occur in sarcoidosis patients compatible with other intertitial lung diseases . Impairment of gas transfer usually occurs in advanced pulmonary sarcoidosis there by is not a reliable prognostic parameter. The six-minute walk test (6MWT) may reveal decreased exercise capacity in sarcoidosis. Desaturation depends on many factors including lung function, cardiac status, and muscle strength. Reduced
(6MWT) is usually associated with advanced lung disease in
Lung function tests are insensitive as prognostic markers
for sarcoidosis patients. First, no single pulmonary function
variable is indicator of disease severity. Second, pulmonary
functions are dependent on many factors including cardiac
status, muscle strength, patient performance, and co morbid
diseases. Third, there are no current thresholds for significant
changes to indicate a severe or chronic outcome for sarcoidosis.
Fourth, the low accuracy of pulmonary function tests due to over
or underestimation of the results render them as insensitive
prognostic markers. As a result, pulmonary function trends do
not always represent disease severity and thereby indicate a
Chest radiology has been the most frequent routine clinical
tool for the evaluation of sarcoidosis patients. Scadding was
the first radiologist to reveal the effect of radiologic stage for
prognosis and stated that in stages I and II the remission was
significantly high compared to stages III and IV . Reich and
Viskum confirmed the association between persistent chronic
sarcoidosis and advanced radiologic stages III and IV. In their
studies radiologic clearance was found to be a good prognostic
sign while stage III was associated higher mortality [12,16].
Chest CT is superior to chest radiology in regard to its high spatial
resolution to assess the lung parenchyma. HRCT is more accurate
for diagnosis by detecting parenchymal distortion, presence and
localization of micro nodules and early fibrotic changes. The
HRCT findings of ground-glass opacity, nodules, septal thickening,
and lineer opacities may be reversible while only architectural
distorsion is irreversible [17-20]. Consequently, in the early
stages (I and II) of sarcoidosis patients the diagnostic sensitivity
and specifity of HRCT is not significant because these lesions do
not have a predictive value. Later stages of sarcoidosis (III and
IV) is frequently irreversible. When radiologically appearent,
these lesions usually indicate irreversible and chronic disease.
Therefore, the prognostic significance of this type lesion is not
useful for predicting the patient prognosis in advance while in
patients with radiologic stages I and II probability of remission
sarcoidosis is high.
A number of laboratory markers including ACE, CRP, Ca, and
neopterin have been used to asses active disease and prognosis.
ACE is produced by macrophages within granulomas and reflects
granuloma burden. Serum ACE is elevated in approximately
in 60% of the patients but both the sensitivity and specifity is
low. ACE is a marker of disease activity rather than prognosis.
Serum calcium is elevated in about 11% while hypercalcuria is
observed in 40%, and nephrocalcinosisin 10% of the sarcoidosis
patients . Persistent hypercalcemia or hypercalcuria may
indicate a chronic disease . Serum CRP may be useful to
identify sarcoidosis patients with extensive and severe disease
but the specifity is low . Other inflammatory markers with indeterminate significance for prognosis are neopterin,
IL-2, tryptase, IL-18, and KL-6. KL-6 is considered as the best
prognostic indicator among these immunological markers.
Extra pulmonary organ involvement frequency in
sarcoidosis is variable ranging from limited to ninety percent
[1,3,21]. Multiorgan disease, defined as three or more organs
is usually associated with a severe prognosis. Lupus pernio,
chronic uveitis, cystic bone lesions, and nephrocalcinosis may be
indicators of persistent disease [9,23]. On the other hand, cardiac
and neurosarcoidosis cause a high mortality. Clinical diagnosis
and involvement of these organs is discordant. Presence of
spinal cord disease and intracranial mass are unequivocally
relevant with a poor outcome. Recently Yanardag et al.  have
shown that diffuse endobronchial involvement identified by
bronchoscopic biopsy is a severe prognostic hallmark.
The role of genetics is well established in sarcoidosis
patients. The frequency of sarcoidosis in the first degree
relatives is significantly high and approaches to fifteen percent.
HLA-DRB1 and HLA-DQB1 allels regulate the susceptibility to
sarcoidosis [25,26]. The interaction between antigen, HLA II
molecules, and T cell receptors is crucial for sarcoidosis. The
DRB*301 is associated with occurrence of Löfgren syndrome
with a benign prognosis while DR15 and DR16 genotypes have a
persistent chronic disease [27,28].
HLA phenotypes may be relevant with specific organ
involvement. HLA-DRB3 is associated with bone marrow
disease, HLA-DPB1*0101 with hypercalcemia, and HLADRB1*
0401 with salivary gland and eye involvement.
HLA-B*07 and *08 are relevant with sarcoidosis risk [1-3,25].
HLA-DRB1*15 is more frequent in skin disease while HLADRB1*
0803 in neurosarcoidosis .Genetic predisposition is
the most important factor for the development of any disease.
The interaction of genetic, hormonal, and environmental effects
should be kept in mind for sarcoidosis. The variable course
of sarcoidosis may also be explained by the different genetic
phenotypes of the patients.
The presentation, clinical manifestations, and outcome
of sarcoidosis is highly variable. Identification of sarcoidosis
patients with a worse prognosis is the hallmark of a successful
treatment. The heterogeinity of pulmonary function impairment
and radiologic changes together with the limitations of
significant change thresholds is the main dilemma for
clinicians. Laboratory and genetic investigations share the same
predicament to determine the outcome of sarcoidosis. Presence
of various clinical factors like lupus pernio, cardiac, cerebral, or
diffuse endobronchial involvement appear to be the best criteria
to determine the prognosis. Cardiac or neurosarcoidosis are not
helpful criteria since they are already manifestations of advanced
disease in most of the patients. For precise identification of
prognostic factors further studies with large and heterogenous sample sizes are needed. On the other hand, the sensitivity and
specify of current prognostic factors like hypercalcemia, lupus
pernio, multiple organ disease, and diffuse endobronchial
involvement may be increased by performing further metaanalytic