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Editor—Hearing loss owing to genetic causes has a reported prevalence of 1 in 1000 births and among these 15-30% are associated with other abnormalities, although only a small number are associated with oral and dental disorders.1 Heimleret al 2 reported two sibs with a combination of sensorineural hearing loss, amelogenesis imperfecta, and nail abnormalities (McKusick No 234580). We describe a further case here and extend the phenotypic spectrum of this syndrome.
A 12 year old girl presented with a combination of unilateral sensorineural deafness and amelogenesis imperfecta. She was born at term following a normal pregnancy and had a birth weight of 3200 g (50th centile). There was no consanguinity within the family; her mother was aged 25 and her father was aged 29 at the time of conception. She had no major illnesses in the first years of life and all her developmental milestones were achieved within normal limits. At the age of 7, it was discovered that she had unilateral hearing loss and subsequent investigation showed that she had profound sensorineural deafness on the left, hearing on the right being normal. At the time her mother felt that she may have had reduced hearing in the left ear for about two years before the diagnosis was made. At the age of 8 years, there was evidence of extensive enamel discoloration in her permanent dentition and amelogenesis imperfecta was diagnosed. Her primary dentition was reported as having erupted on time and the remaining primary teeth had a normal appearance. There was no history of intellectual impairment and she was doing well in mainstream education. Her family history was unremarkable; her parents were unrelated and there was no history of sensorineural deafness or enamel defects on either side of the family. She has one younger brother who is unaffected.
On examination she was on the 10th centile for height and the 25th centile for weight. She had a fair complexion (fig 1) and examination of her nails showed multiple transverse grooves (Beau's lines) on several fingers and toes (fig 2A, B). There was no evidence of leuconychia. Examination of her teeth showed dental overcrowding and extensive enamel discoloration (fig 3). Ground sections of permanent premolars, extracted for orthodontic purposes, showed dentine and enamel of normal thickness. It seems likely therefore that the amelogenesis imperfecta is a hypomineralised rather than a hypoplastic variant.
The combination of sensorineural hearing loss, amelogenesis imperfecta, and nail abnormalities was first reported by Heimler et al. 2 They suggested that the syndrome could be the result of a single gene affecting derivatives of the ectodermal tissue because the abnormalities described have a common embryological origin in the ectoderm. This theory is made more probable by the reporting of a second case here.
Heimler et al 2 described two sibs who both had profound bilateral sensorineural hearing loss, amelogenesis imperfecta of the permanent dentition, and Beau's lines. Inheritance of this syndrome was postulated to be autosomal recessive and our case does not allow us to draw any further conclusions on this. To date, no other cases of Heimler's syndrome have been identified (A Heimler, personal communication). The case described here had unilateral sensorineural hearing loss, a hypomineralised form of amelogenesis imperfecta, and Beau's lines and it is likely that this is a similar association to the originally described syndrome, which extends the phenotypic spectrum (table 1).
It is interesting that the hearing loss was diagnosed at a relatively late age and the mother's observations suggest that it had previously been normal. In the original report, deafness was diagnosed in the second sib at the age of 2½ years, hearing having been normal for the first two years. It thus seems that the hearing loss in this condition is not congenital.
Amelogenesis imperfecta is classified according to the predominant clinical and radiographic appearance of the enamel defect and on the mode of inheritance of the trait.3 The amelogenesis imperfecta described here is unusual in that only the permanent teeth are affected, which makes non-genetic causes less likely. The diagnosis of hypoplastic amelogenesis imperfecta in the original case report was made on radiographic evidence and a histopathological examination was not performed. The hypomineralised amelogenesis imperfecta in our case illustrates the variation in phenotype that can occur in this condition.
Beau's lines are transverse lines across the nails that can arise from severe illnesses, such as sepsis, AIDS, or bullous pemphigoid, and can also be physiological in menstruating women.4 They can be quite subtle as in this case where they only became apparent once nail varnish had been removed. Our patient had no evidence of punctate leuconychia which was described in the original family, which could suggest that this feature may have been an incidental finding in the original report, as it is a common normal variant. Our case also emphasises the importance of careful examination of the nails in patients with a combination of impaired hearing, which may only be unilateral, and dental pathology.