ESPE Abstracts

Background: Hereditary hypophosphatemia (HH) are rare diseases, characterized by excessive renal phosphate wasting.

Aim: The study aims to describe the burden of disease across age groups in individuals with HH.

Methods: The case population was identified in the Danish National Patient Register (DNPR) from 1977 to 2019 based on relevant diagnosis codes. A journal audit was performed to verify the diagnosis of HH. Controls matched 50:1 with HH by gender, birth month/year, was randomly selected using the Danish Civil Registration System. Data on co-morbidities were retrieved from DNPR.

Results: The dataset comprised 120 individuals with HH matched with 6000 controls. Children with HH had a greater descriptive relative risk (dRR) of 3.2 for having pneumonia. Children with HH were diagnosed earlier than controls (P = 0.009), where the risk for pneumonia was significantly higher during the first two years of life in HH (P = 0.005), and their lifelong risk was significantly higher (P = 0.015). Children with HH had significantly higher dRR for hearing loss of 4.9 compared to controls (P = 0.001) with an increased lifelong risk (P <0.001). At the age of 10y, 5.8% of HH compared to 0.8% of controls (<0.001) had a diagnosis of hearing loss and the earliest age of a diagnosis of hearing loss in HH was at age 3y. During childhood, the risk for obesity in HH was equal to controls (P = 0.376), but the lifelong risk was increased in HH (P = 0.011) and obesity was diagnosed increasingly from age 25y. The dRR for being diagnosed with a reaction to severe stress or adjustment disorders was increased to 3.3 in children with HH compared to controls (P = 0.019), and this risk was increased in HH throughout the life span (P = 0.049). The risk for being diagnosed with a depressive episode was not increased in HH compared with controls throughout the lifespan (P = 0.47), but adults with HH were diagnosed with a depressive episode at an earlier age compared to controls (age 26y vs. 34y, P = 0.008), and this increasingly around age 20y.

Conclusion: Children with HH compared to controls had a significantly higher dRR of being diagnosed with pneumonia, hearing loss, and reaction to severe stress or adjustment disorders, in addition to a higher lifelong risk. Strikingly, a depressive episode was seen at an earlier age in HH coinciding with the time for transition to adult life and adult care. This underlines the importance of focusing on mental health during early adulthood in HH.