LAUSR

Background Hereditary Hemochromatosis (HH) is a common inherited disorder and characterised by an excess iron accumulation in several organs with consecutive organ dysfunction.1 Apart from the liver, the joints are a major site of excess iron deposition. Joint pain counts among the most frequent (>50%), earliest, and most debilitating symptoms of HH.2 To date, joint health status in HH patients is routinely assessed on hand radiographs.3 However, plain radiography is a low-resolution, 2D-technique with limited sensitivity to detect early joint changes or to monitor subtle progression of joint damage.4 With the advent of high-resolution peripheral quantitative computed tomography (HR-pQCT), a promising imaging tool has emerged allowing for in vivo 3D characterisation of human joint microstructure at a spatial resolution of 130 µm.5 Due to its high sensitivity to detect and monitor subtle, short-term joint changes, HR-pQCT has been successfully applied to patients with RA.6 However, to date, HR-pQCT has not been used to characterise joint and bone changes seen in HH arthropathy. Objectives Here, we aimed to investigate in a cohort of HH patients 1) if the usage of HR-pQCT is feasible on HH patients; 2) to quantify joint microstructure of metacarpophalangeal joints (MCP2–4) in this specific patient group; and 3) investigate the relationship between HR-pQCT-derived joint microstructural parameters and clinical outcomes. Methods 25 HH patients were enrolled and their HH history and treatment were recorded. MCP joints of all patients were imaged at a clinical HR-pQCT system (XtremeCT, Scanco Medical AG). 330 images were acquired covering MCP 2, 3 and 4. The joint space (JS) morphology of each MCP was quantified from the HR-pQCT images semi-automatically4 and volume (JSV), joint space width mean (JSW), JSW variance (JSW.SD), and JSW asymmetry (JSW.AS) were calculated. Results Out of the 75 MCP joints available for analysis, 79% were successfully segmentable, and 19% required semi-manual intervention to separate the individual bones. 3 joints were excluded due to motion artefacts, and 1 joint was unsegmentable. HH patients were 32–72 years old, in 64% male, and had been diagnosed with HH 2 months to 40 years ago. 15% were pain free at the study date. HH patients with pain showed significantly lower JSV at MCP 2 and 4 (p=0.009) and exhibited a significantly higher joint asymmetry in MCP 3 (p=0.012) compared to their pain free colleagues. When looking at clinical correlations we found that time since HH diagnosis was positively correlated with the MCP4 JSW asymmetry (R2=0.451, p=0.040) and MCP 4 JSW.SD (R2=0.475, p=0.030). The number of phlebotomies since diagnosis was strongly correlated with the JSW.SD (MCP2–4: 0.4552<0.581,p<0.050) at all MCP sites.Abstract FRI0596 – Figure 1 3D surface reconstructions of the MCP3 with the local joint space width mapped into the joint space in psuedo-colour. Blue and green colours reflect narrow joint space width, while red colours code for a broader joint space width. A) 55 year old male with a BMI of 21.9 kg/m2 who has been diagnosed with hemochromatosis 8 years ago, but received only occasionally phlebotomies. B) 48 year old male (BMI 22.9 kg/m2) with a diagnosis of hemochromatosis of 8 years who received regular phlebotomies every 2 months. Both patients presented at the study date with hand pain. Note the larger and more symmetrical joint space width in patient B. Conclusions Our study provides the first evidence that joint space assessment of MCPs via HR-pQCT in patients with hereditary hemochromatosis is feasible and can provide a thorough structural joint characterisation and thus support the physician in his initial HH arthropathy assessment. Our findings suggest, that regular phlebotomies since diagnosis may preserve joint space morphology leading to a more evenly maintained joint space. However, larger studies are needed to validate our results. Disclosure of Interest None declared