Background Familial Mediterranean Fever (FMF) is an autosomal recessive disease characterized by recurrent inflammatory febrile attacks of peritonitis, pleuritis and arthritis. Vasculitis, pulmonary hemorrhage, infarction, or infiltrates1, diffuse opacities and hilar adenopathy2, pulmonary hypertension due to amyloidosis3 may be associated or developed in a course of the disease. However these complications have been reported only rarely.
Objectives To evaluate the respiratory involvement and pulmonary consequences in FMF we measured blood gases, nitric oxide (NO), endothelin (ET-1), C-reactive protein (CRP) and serum amyloid-A (SAA) in 102 FMF patients with respiratory complaints during attack-free period.
Methods FMF patients were divided into two groups, with and without amyloidosis. Oxygen tension (PO2), carbon dioxide tension (PCO2) and oxygen saturation (O2Sat) were measured in capillary and venous blood. Simultaneously serum NO, plasma ET-1, CRP and SAA were determined. Student's t-test and Pearson correlation analysis were used.
Results Blood gases values (mean ± SD) were within normal ranges in patient group without amyloidosis (n=53), and were slightly decreased in amyloidosis patients group (n=49) (PO2 82.2±9.73 mm Hg, PCO2 39.4±3.83 mm Hg, O2Sat 94.6±3.8% vs. PO2 74.5±12.13 mm Hg, t=3,529, PCO2 35.1±5.2 mm Hg, t=4.69, O2Sat 88.8±12.4%, t=3.14 P<0.00001). In the group of patients without amyloidosis O2Sat was positively correlated with NO and negatively with ET-1 levels (r=0.271, p=0.05 and r=-0.570, p=0.000), PO2 showed negative correlation with ET-1 level (r=-0.479, p=0.479), and both PO2 and O2Sat were negatively correlated with CRP (r=-0.492, p=0.000; r=-0.534, p=0.000, respectively). In the group of patients with amyloidosis there was no correlation between blood gases values and NO, whereas PCO2 was negatively correlated with ET-1 levels (r=-0.371, p=0,009) and CRP (r=-0.302, p=0.035). There was no correlation between blood gases and SAA in both groups.
Conclusions Blood gas abnormalities in patients with FMF are related to disease severity, inflammation and vascular (endothelial) alteration. Correlations between PO2, O2Sat and ET-1 and CRP in FMF patients without amyloidosis suppose possible high risk of pulmonary vascular manifestations. Mild hypocapnia in FMF patients with amyloidosis associated with an increase in plasma ET-1 and CRP, whereas hypoxia is not correlated with both ET-1 and CRP. Concerning the latter finding it could be due to the limitation of our study and necessity of arterial blood examination to assess the oxygenation status. Taking into account that capillary blood accurately reflects arterial PCO2 4 we may conclude that patients with FMF-amyloidosis have an increased risk of pulmonary complications.
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Acknowledgements The author thanks Anahit Davtyan and laboratory staff for their collaboration.
Disclosure of Interest : None declared