Development of Paget’s disease of bone in adults inheriting <i>SQSTM1</i> mutations: a long-term follow-up

In a 2015 study of <i>SQSTM1</i> mutation carriers who had initial negative bone scintigraphy, we found that the rate of development of Paget's disease of bone (PDB) over 5 yr was low. We report here an additional 8-yr follow-up of this cohort, exploring the hypothesis that the rate of development of PDB would increase as the cohort aged. In the current study, 21 of 24 subjects from 2015 who had a negative bone scintiscan at baseline and at first follow-up, had a repeat scintiscan and measurement of total serum alkaline phosphatase activity. Two subjects with P392L mutations were identified as having PDB (monostotic in one case, 2 bones involved in the other), giving an incidence during this follow-up period of 1 per 87 patient years or 11.9 per 1000 patient years. This was contrary to our hypothesis, as the rate of development had decreased as the cohort aged. When we compared by survival analysis the age at presentation with symptomatic PDB in the older generation, we found that the age of onset was later and disease severity in the affected relatives was markedly less than in their clinically affected parents (<i>p</i> < .001). Our results are in keeping with other recently published studies and the general secular trend in PDB and support the idea that an important environmental-genetic interaction is involved with the development of PDB and that exposure to the putative environmental factor has substantially reduced.