Albertine Donker

Chapter 8 282 RESULTS Patient characteristics IRIDA patients We included 21 patients in the IRIDA group. Seventeen out of 21 patients were diagnosed between 2010 and 2015 and were described earlier. 11 Four out of 21 IRIDA patients were diagnosed between 2015 and 2019 and have not been described elsewhere. Clinical, biochemical and genetic characteristics of the IRIDA group are presented in Table 1A . The bi-allelic affected group consisted of 7 females and 4men, themono-allelic affected group of 9 females and 1 male. MLPA showed no large deletions and/or duplications in the as ‘healthy’ considered TMPRSS6 allele. Age at time of genotypic confirmation of IRIDA ranged from 1 to 38 years in the bi-allelic affected group, with a median age of diagnosis at 9 years old (IQR 6-21 years). In the mono-allelic group evaluation of IRIDA took place at a median age of 40.5 years (IQR 31-48 years). Patient characteristics IDA controls The IDA group consisted of 39 patients, of whom 29 (74 %) were female. Clinical, biochemical and treatment characteristics of the IDA patients are presented in Table 1B . All controls had a microcytic anemia according to the WHO definition (MCV ≤80 fL and Hb <13.5 g/dL for men; <12 g/dL for women) 36 with a TSAT <15%, of which 95 % had TSAT levels ≤10%. Median ferritin level was 9.0 µg/L (range 2-38 µg/l), median CRP was 1.8 mg/L (range 0.2-8.1 mg/L). Remarkably, 9 out of 39 IDA were overweight (23%) and 17 out of 39 IDA controls were obese (44%) according to international cut-off points for BMI. 37 Apart from IDA, 18 out of 39 (46%) patients had comorbidity, whereby diabetes mellitus was the most common condition (12 out of 18=67%). Sixteen out of 39 IDA cases (41%) had a normal kidney function (defined as eGFR >90 ml/min/1.73 m 2 ) and 17 out of 39 patients (44%) had a mild to moderately decreased kidney function (eGFR >30-< 90 ml/min/1.73 m 2 ). In the other 6 out of 39 (15%) renal function was not determined. Causes of IDA of the control subjects are summarized in Table 1B . In 21 out of 39 patients (54%) and underlying cause for IDA was found with gastrointestinal bleeding being the most prevalent cause (31%) In 18 out of 39 patients (46%), IDA was unexplained after extensiveworkup, including gastroscopy, colonoscopy and video capsule endoscopy. In these cases, IDAwas attributed to an insufficient diet and/or the use of certainmedication that enhances the risk of gastrointestinal bleeding (e.g. anticoagulants, antithrombotic agents and NSAIDs) or diminishes iron absorption (e.g. proton pomp inhibitors). In the