Proteinuria-associated nutcracker syndrome: an amyloid-negative familial Mediterranean fever patient

Abstract

Sir, Familial Mediterranean fever (FMF) is an autosomal recessive disease, and the most important complication is amyloidosis which leads to end-stage renal disease [1]. Nutcracker syndrome (NCS) is a rare clinical condition manifested by haematuria, proteinuria, gonadal varicose veins and side pain, all due to compression of the left renal vein and renal congestion [2]. Not all the cases of proteinuria in familial Mediterranean fever are due to amyloidosis, and the ‘nutcracker syndrome’ can be one of the confounding causes. Case A 22-year-old female with an 11-year history of FMF was referred to our clinic for sustained proteinuria. The patient had undergone multiple kidney biopsies with no specific pathology and negative amyloid tests. Physical examination was unremarkable. Laboratory results revealed the following: white blood cells 6000/mm3, haemoglobin 10 g/dL, erythrocyte sedimentation rate 78 mm/h, creatinine 0.46 mg/dL, urea 12 mg/dL and albumin 3.2 g/dL. Urine sediment was normal, and 24-h urinary protein was 1.1 g/day. The immunological markers were negative. Renal Doppler ultrasound revealed a narrowing in diameter of the left renal vein at the aortomesenteric level and also mild dilation 2 cm distal to that level. The findings of the CT angiography study confirmed anterior NCS and compression of the anteroposterior and craniocaudal diameter of the left renal vein at the anterior aspect of the aorta as well as dilation of the left renal vein in the mid-section (Figure 1). Due to the lack of pathology in all three renal biopsies, it was found that the patient’s proteinuria was due to NCS. Because of the mild symptoms, no invasive treatment was given, and treatment with an ACE inhibitor was initiated. Fig. 1 CT angiography revealed a dilated left renal vein after passing between the aorta and superior mesenteric artery. Discussion The association between FMF and non-amyloid glomerulopathy is unusual. Previously, IgA and IgM nephropathies and polyarteritis nodosa (PAN) have been reported [3,4]. NCS, characterized by the compression of the left renal vein between the superior mesenteric artery and the abdominal aorta, was first named in 1972 by De Schepper [2]. Renal Doppler ultrasound, CT angiography, magnetic resonance angiography or venography can be used for the documentation of the degree of left renal vein compression [5]. NCS presented with FMF was first reported in 2009 by Ozcan et al., which was similar to our case [6]. Here, we presume that actually, from the beginning, our patient’s proteinuria was due to NCS. For mild haematuria or proteinuria, conservative treatment is proposed, whereas for recurrent severe haematuria or flank pain, endovascular stent surgical treatment is proposed for NCS [2]. Here, we proposed the conservative treatment. Mild proteinuria is a benign condition, but it can be persistent, and therefore, conservative treatment should be continued for several years. Although amyloidosis should be considered first in clarifying the aetiology of proteinuria in FMF, NCS, another rare entity, should be kept in mind and should also be excluded by non-invasive techniques when possible or by invasive techniques if necessary in FMF patients. Conflict of interest statement. None declared.