Bilateral renal vein thrombosis secondary to methylene tetrahydrofolate reductase mutation: a rare case

Bilateral renal vein thrombosis secondary to methylene tetrahydrofolate reductase mutation: a rare case To the Editor, Renal vein thrombosis (RVT) is a rare but serious complication that is associated with many systemic disorders [1]. Thromboembolic complications, especially RVT, are frequent in nephrotic syndrome and are very prevalent in membranous nephropathy [1]. Trauma, oral contraceptives , infection, inherited pro-coagulant defects, lupus an-ticoagulant, antiphospholipid syndrome and severe dehydration are the other most common causes of RVT in adults [1]. Herein, we describe bilateral RVT secondary to heterozygous methylene tetrahydrofolate reductase (MTHFR) mutation. During differential diagnosis, we wish to alert physicians that RVT may be a cause of flank pain and haematuria, even in subjects with no known risk factors for thrombosis. Because early diagnosis with appropriate treatment is associated with good prognosis, the present case highlights the importance of thrombophi-lic investigation in all patients with suspected RVT to avoid missing this rare but frequently curable condition. To the best of our knowledge, this is the first reported case of RVT associated with MTHFR mutation in the adult population. A 29-year-old woman was admitted to the hospital after complaining of sudden onset right flank pain. Her medical history was unremarkable and she was not using any drugs or oral contraceptives. She had one healthy 5-year-old child and no reported abortion or miscarriage. There was no family history of thrombosis. On admission, her vital signs and physical examination were normal except for right flank tenderness. Admission laboratory analyses showed haemoglobin = 10.5 g/dL (12–16 g/dL), leucocyte = 12.3 × 10 9 /L, platelet = 515 × 10 9 /L, mean corpuscular volume (MCV) = 73.6 fL (80–96 fL) and C-reactive protein = 16 mg/L (0–10 mg/L). Her urinalysis showed microscopic haematuria. Her renal and liver function analyses were all normal. Chest and abdominal X-rays and electrocardio-gram showed nothing remarkable. Abdominal ultrasonog-raphy (US) was suspicious for thrombosis of the right and left RV without any evidence of masses or hydronephrosis. Further investigation with Doppler US revealed absence of blood flow at the right RV, total continuous thrombosis from the right RV to the vena cava inferior (VCI) and a partial thrombosis at the left RV extending to the VCI. The patient was diagnosed with bilateral RVT. After these findings were confirmed with renal venography, manual thrombus aspiration was performed and optimal restoration of bilateral RV was obtained (Figure 1). Although a partial thrombus remained because …