Endocrine Abstracts

Background: Hereditary hypophosphatemia (HH) are rare diseases, characterized by excessive renal phosphate wasting and inappropriately low 1,25-dihydroxy-vitamin D causing hypophosphatemia. In children, the disease manifests as rickets and osteomalacia, in adults osteomalacia.

Aim: The study aims to describe the co-morbidities more prevalent in adults (18y+) with HH and the median age at first diagnosis compared to controls.

Methods: The case population was identified in the Danish National Patient Register based on five diagnostic codes referring to rickets or hypophosphatemia. A journal audit was performed based on all cases identified in Region of Midt Jutland and on available medical files from the remaining four regions in Denmark to verify the diagnosis of HH based on predefined diagnostic criteria. The background population (control) matched by gender, birth year and month, was randomly selected using the Danish Civil Registration System matching fifty controls to each adult with HH. Data on co-morbidities were retrieved from the Danish National Patient Register.

Results: The dataset comprised 98 adults with HH matched with 4.893 controls. Arthrosis was significantly more prevalent in adults with HH compared to controls (P<0.001) and first diagnosed at a significantly earlier median age (37.5y vs 55.5y, P<0.001). Knee prosthesis and osteotomy were significantly more prevalent in adults with HH (P<0.001 both); although younger in age at first registered contact, it was not significant. Hyperparathyroidism, renal failure, and hypertension were more prevalent in adults with HH (P<0.001, P<0.001, and P=0.002, respectively), also being diagnosed significantly earlier in adults with HH (median age 35.0y vs 62.0y, P=0.010; 40.5y vs 62.0y, P=0.027; and 41.5y vs 58.0y, P=0.027, respectively) compared to controls. Chiari I malformation, spinal stenosis, hearing loss, obesity and diseases of pulp and periapical tissues were more prevalent in adults with HH compared to controls (P<0.001, P<0.001, P<0.001, P=0.002 and P=0.001 respectively), but with no difference in age at presentation. Depressive episode(s) were of similar prevalence, but the median age at presentation was younger for adults with HH (26.0y vs 34.0y [P=0.008]).

Conclusion: This retrospective analysis revealed a significantly higher prevalence of co-morbidities already well-known in adults with HH, identifying that in some cases a first contact was at a significantly earlier age compared to controls. Clinicians taking care of adults with HH need to be aware of co-morbidities occurring at an earlier age to identify and initiate correcting actions to limit progression of morbidities in adults with HH.