Hearing impairment in familial X-linked hypophosphatemic rickets

Hearing impairment in patients with X-linked dominant hypophosphatemic rickets (XLH) is likely part of the natural history of the disease, developing during adulthood. Therefore, whereas close follow up and hearing monitoring is recommended in adults, serial audiograms in children with XLH are not justified. Furthermore, in a child with XLH and hearing impairment, other etiologies should be explored. Hearing impairment in XLH patients has been reported a few times in the 1970s and 1980s [1, 2, 4, 5]; however, it was our impression that our pediatric XLH patients did not manifest clinical hearing impairment. Therefore, in order to better clarify the association between XLH and hearing status, and consequently provide information regarding patients’ management, we prospectively evaluated the hearing status in our XLH patients and their afflicted parents. Hearing evaluations including audiometry, tympanometry and stapedial reflex thresholds recording were performed in 16 children with XLH (age 1–18 years, median 9.0 years, six males) and all of their ten afflicted parents (age 22–55 years, three male). None had a history of treatment with ototoxic drugs, noise exposure, previous ear surgery or chronic ear disease. Of 16 children, 15 demonstrated normal hearing. One with bilateral profound hearing loss was found to have a Mondini congenital inner ear malformation, documented by a temporal bone CT scan. Two adult males and one female, all with severe XLH-related orthopedic manifestations, demonstrated sensorineural hearing loss. More than two decades passed since hearing impairment was first described in XLH [5]. Table 1 summarizes the main findings of previous studies that have reported on this association, showing evidence of hearing impairment in a significant percentage of adult XLH patients versus minimal incidence of hearing loss in children [1, 2, 4, 5]. We compared the hearing status in a relatively large group of XLH children in a wide range of ages with that of their afflicted parents. None of our children had a hearing impairment attributable to XLH. The only child with hearing impairment was the one with a Mondini inner ear malformation which is believed to result from a developmental arrest of the membranous labyrinth during the first trimester of pregnancy [3], and is not known to be associated with rickets which is a post-natal disease. In contrast to the normal hearingwe found in ourXLH children, three of their ten parents had sensorineural hearing loss. These patientswere under 52 years old; hence presbyacusis was ruled out. Since in all three etiologies other than the disease process were excluded and in the light of the fact that all had severe orthopedic manifestations of rickets, we suspect that their hearing impairment is part of the disease process. They were referred to adult otolaryngologists for further management. Even though two of the earlier studies [2, 5] found hearing impairment in a very few children, later studies which investigated much larger cohorts of children [1, 4] as well as ours, did not find evidence of XLH-related hearing impairment in childhood. Therefore, it cannot G. Fishman Department of Pediatric Otolaryngology, ‘‘Dana’’ Children’s Hospital, Tel-Aviv Medical Center, ‘‘Sackler’’ School of Medicine, Tel-Aviv University, Tel-Aviv, Israel