Mo112systemic Oxalosis in Primary Hyperoxaluria Type 3 – Are the Patients at Risk?

Abstract

Background and Aims Primary Hyperoxaluria type 3 (PH3) is said to be the less problematic form of PH and with low risk of chronic kidney disease (CKD) and end stage renal disease. However, a recent OxalEurope registry evaluation reported both urine and plasma oxalate levels in a comparable range as in PH1 and PH2 patients. In addition, PH3 patients remain symptomatic with recurrent kidney stones, even in adulthood, and 24% of the 95 patients evaluated were on CKD ≥ 2 at last follow up. Hence, it was speculated, that PH3 patients may also be on risk to develop systemic oxalate deposition. Method We retrospectively analyzed the imaging procedures performed so far in patients regularly seen at the German Hyperoxaluria Center, which included: eye exams; x-rays of the hand; bone MRI (3 Thesla of the left knee and proximal tibia); and Speckle tracking echocardiography using 2D Cardiac Performance Analysis VC (TomTec Imaging Systems GmbH, Germany), which measures changes in global longitudinal strain (GLS), an index of left ventricular contractibility. The normal range for GLS is ≤18%. All patients or parents signed an informed consent. Results From the 49 PH3 patients registered at the German Hyperoxaluria center, 12 pediatric and 4 adult patients are seen on a regular basis, at least twice a year, and the rest are followed in other centers. All the 16 patients were in stable kidney function and in no less than CKD 2. Eye examination was performed in six patients and was normal in all. Four patients received an x-ray of the left hand, which was normal in 3, but in one patient with a problematic clinical course (multiple stone removal procedures, decline in GFR), tiny sclerosing areas, although no true metaphyseal bands, were seen at caput MCP IV and the thumb. Therefore, MRI of the left knee and proximal tibia was performed in this and another patient, which showed no signs of systemic oxalate deposition. Speckle tracking echocardiography was done in 6 patients and was abnormal in one (GLS – 17.3 and left ventricular hypertrophy) and borderline in the twin sibling (GLS – 18.6). The patient with the abnormal GLS also had salivary stones in the parotid gland, as were also found in his other, older sibling in a routine x-ray of the jaw before orthodontic treatment. Conclusion Although this is currently only data of a small cohort of patients, the parameters available so far show, that systemic oxalate deposition may also occur in PH3. Based on our experience on PH1, we regard Speckle tracking echocardiography as the best parameter to detect early systemic calcium-oxalate depositions. Hence the reduction in global longitudinal strain, thus ventricular contractability, is a clear proof of such deposits. Of course, data in more patients are needed to elucidate the true risk of systemic oxalate deposition and we are therefore currently screening all our PH3 patients.