Report of Two Dental Patients Diagnosed with Hypophosphatasia

Abstract

Hypophosphatasia is a rare inherited skeletal disorder characterized by defective bone mineralization and tissue non-specific alkaline phosphatase (TNSALP) deficiency, with mutations in the gene encoding the TNSALP isozyme the cause. As for dental manifestations, premature loss of primary teeth due to disturbed cementum formation is well known and tooth roots in affected patients are not able to adequately attach to absorbed alveolar bone due to malformed cementum. We report spontaneous early exfoliation along with mild to severe mobility of primary anterior teeth in 2 child patients referred to pediatric dentists from a general dental practitioner. Case 1 was a 1-year-7-month-old boy with 3 mandibular incisors exfoliated, while Case 2 was a 3-year-3-month-old girl with 1 mandibular central incisor exfoliated. The possibility of hypophosphatasia was considered and the patients were referred to the Pediatric Clinic of Osaka University Medical Hospital, where each was diagnosed with hypophosphatasia (odonto type). We performed repeated periodontal treatments and applied removable partial dentures in both cases, which solved esthetic and functional problems. Although the incidence is quite low, it is important to diagnose hypophosphatasia as early as possible for planning general and dental preventive approaches. In patients with mild forms, such as odonto and childhood types, early exfoliation of primary teeth identified in a dental examination can occasionally lead to early diagnosis of hypophosphatasia. In addition, dental findings obtained by a dentist are useful to identify patients with a risk of hypophosphatasia, who can then be immediately referred to a pediatrician for more detailed systemic examinations. Thus, a cooperative relationship between pediatricians and pediatric dentists should be regarded as necessary. This is the first known report to describe cases of hypophosphatasia diagnosed after referral from a pediatric dentist because of typical dental findings for the disorder.

Japanese nationwide survey of hypophosphatasia reveals prominent differences in genetic and dental findings between odonto and non-odonto types

“…Dental symptoms are often the first clue for an early diagnosis for some patients with HPP 3 . Early tooth exfoliation can sometimes lead to a diagnosis of mild-type HPP, such as odonto and childhood types [11,12]. In this study, the mean age at diagnosis for patients with odonto-type HPP was significantly younger than that for patients diagnosed with childhood-type HPP.…”

“…Teeth might be more sensitive to serum ALP levels than other calcified tissues in patients with odonto-type HPP. In mild-type patients with one or two exfoliated teeth before medical diagnosis of HPP, a relevant differential diagnosis of dental trauma versus HPP is difficult [12,27]. In our study, 80% of patients reported mobility of the primary teeth, which may be exfoliated with light pressure.…”

“…Previous studies have reported that odonto-type HPP cases sometimes shift to childhood- or adult-type HPP over time [7,12]. Therefore, the identification of odonto-type cases is important for early diagnosis and continuous medical management.…”

“…Patients with severe-type HPP, such as perinatal or infantile types, receive general care from medical doctors before or soon after birth. However, in less-severe types, such as odonto or childhood types, dental signs are often the first clues toward a diagnosis [7,11,12].…”

Ankylosed Primary Molar in a Japanese Child with Hypophosphatasia

“…Typical dental manifestations of HPP are known to include early exfoliation of primary incisors before 4 years of age [ 6 , 7 , 8 ]. This manifestation sometimes leads to diagnosis of mild HPP (e.g., odonto and childhood types) [ 9 , 10 ]. To the best of our knowledge, there have been few reports regarding long-term follow-up in patients with dental manifestations of HPP after early exfoliation of primary incisors [ 11 , 12 , 13 ].…”