Electronic Medical Record and Clinical Evaluation of Two Patient Cohorts at Risk of Hypophosphatasia: Family History is an Underutilized Tool to Diagnose Patients with Rare Disease

Abstract Background: Family history (FH) is a powerful tool in screening and testing for chronic disease, oncologic conditions, and other genetic diagnoses, and is dependent upon observing patterns of features inherited across generations. Despite acceptance of FH as a fundamental part of a genetic medicine evaluation, there are limited data in other medical fields about its utility and benefit to patients. Methods: We evaluated two patient populations at-risk of a rare metabolic condition-- hypophosphatasia (HPP)—for the quality and quantity of FH data in their medical records. Population 1 was derived from patients seeking evaluation for a low bone density diagnosis at the Johns Hopkins Greenberg Center for Skeletal Dysplasias (GCSD); population 2 was identified through a targeted electronic medical record (EMR) query of low serum alkaline phosphatase (AP) measurements obtained through the Johns Hopkins Clinical Laboratory. Results: In population 1 (n = 38), 27 (71%) were confirmed to have HPP. Of these, 14 (52%) presented with FH information in the EMR from 3 or more family members, and in 4 (15%) FH was suggestive of HPP. In population 2 (n=348), a similar proportion of subjects had 3 or more family members mentioned in the EMR (183 or 53%), but only 3 subjects (1%) included sufficient detail to determine that the family history was suggestive of HPP. Notably, once all patients in population 1 completed a medical genetics evaluation and HPP was confirmed, 20 (74%) had probable affected family members identified through obtaining and analyzing a pedigree. After cascade testing was offered to these family members, 17 patients (71%) from population 1 had at least one family member with HPP confirmed at a molecular level. Conclusions: Based on these results, we propose that a full genetic medicine evaluation of those subjects from population 2 at highest risk of HPP would confirm HPP in many of them and identify similarly affected family members. We propose that taking a FH refines the diagnostic precision for patients with low bone density and identifies affected family members, and that HPP is likely more prevalent than previously thought.