Introduction
Waardenburg syndrome was initially described in 1951 by the Dutch ophthalmologist and geneticist P.J. Waardenburg and it is an autosomal dominant condition, with variable penetration and expression.
The clinical signs are represented by:
medial canthus and inferior lachrymal point displacement;
prominent and broad nasal root;
white hair forelock;
total or partial iris heterochromia;
congenital hearing loss.
Other characteristics have been observed and added to the clinical picture by other authors, such as cutaneous hypopigmentation, early graying hair, peculiar facial aspect, iris hypoisochromia, and retina pigmentary abnormalities, in addition to association with cleft lip and palate. The new criteria accept the non-existence of dystopia canthorum, dividing the syndrome into two types, depending on its presence (type I) or absence (type II).
Waardenburg calculated the incidence of the syndrome among congenital deafness patients as being approximately 1.43% and 1:42,000 in the general population. New studies defined a variation of incidence in Waardenburg syndrome among congenital deafness patients of 0.9% in the study by Partington, 2.07% in the study by Reed, 2.33% in the study by Di George, and 2.8% in the study by Ahrendts.
The specific hearing pathology of Waardenburg syndrome is not always well defined. Some studies reported cochlea hypoplasia, posterior semicircular canal aplasia or hypoplasia, abnormal vestibule and absence of oval window revealed by mastoid Computed tomography scan.
Material and method
Two brothers with Waardenburg syndrome were seen at the Service of Otorhinolaryngology, CEDALVI - Hospital de Reabilitação de Anomalias Craniofaciais, USP, Bauru, in 2001. The brothers (A and B) were aged 19 and 9 years, respectively. They were classified as Waardenburg type I according to the diagnostic criteria proposed by Farrer et al.
We conducted anamnesis, otoscopy, pure tone audiometry and impedanciometry. The degree of hearing loss was determined by assessing the mean values by frequency and the results were classified according to Russo and Santos (1993) and the International Bureau for Audiophonology, which classified hearing loss in degrees of severity: 0 - 20 dB: normal; 20 - 40 dB: mild hearing loss; 40 -70 dB: moderate; 70 - 90 dB: severe, and over 90 dB: profound hearing loss.
Results
The patients were referred from our hearing center. Patient A, 19 years of age, reported deafness noticed by the parents and diagnosed at approximately 1 year of age as bilateral profound sensorineural hearing loss. Patient B referred hearing difficulty on the right, noticed by the parents at the age of 8 years and diagnosed as right profound sensorineural hearing loss, whereas the left ear was normal. In the exams conducted in our center, otoscopy was normal, tympanic membranes were bilaterally intact and type A tympanometry was detected in the brothers. Audiometry showed bilateral profound sensorineural hearing loss in patient A and patient B had right profound sensorineural loss and left moderate-severe loss. Stapedial reflexes were absent in patient A and in patient B they were absent on the right and present on the left, with signs of recruitment. There was no evidence of any other disease that could have led to hearing loss pre, peri or post-natally.
Discussion
Hearing loss is the most preoccupying symptom of Waardenburg syndrome. Originally, Waardenburg estimated that the penetration of the deafness in the syndrome was 20%, however, recent estimates presented 36% to 58% in type I and 57% to 74% in type II. Silva et al. reported that deafness was unilateral in 21% of the patients and bilateral in 46%.Hageman and Delleman observed that in Waardenburg syndrome type I, 28% of the patients presented bilateral deafness and only 8% had unilateral hearing loss, whereas in type II Waardenburg syndrome, 53% of the patients presented bilateral hearing loss and 4% presented unilateral deafness. This difference is probably due to the great variation in expression of this syndrome, especially when isolated characteristics are compared.
The etiology of most cases of Waardenburg syndrome can be the genetic anomaly of autosomal dominant transmission, whose penetration and expression vary considerably, distributed equally in both genders.
It is estimated that 25% of the cases represent a new mutation, as noticed in isolated cases. Waardenburg demonstrated that not all characteristics necessarily have to be present in each patient, but the subjects with partial syndrome may transmit the complete affection to their children. It shows the importance of genetic counseling, reinforced by the fact that deafness normally causes major difficulties to the subjects.
The pathogenesis of the syndrome is still open-ended. Fish suggested that it could be a migration defect of cells to the neural crest during the third month of gestation. From the neural crest originates the melanocytes, sympathetic ganglia and sensorial components of the cranial and spinal nerves, the membranous bones of the face and palate, dentin and visceral ganglia, which seem to explain all the clinical signs described in the literature.
As the main differential diagnosis, we should exclude piebaldism associated with deafness (Woolf's syndrome).
REFERENCES
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1 Otorhinolaryngologist, Master studies under course, Discipline of Human Communication Disorders, HRACF - USP.
2 Resident Physician in Otorhinolaryngology, HRACF - USP.
Affiliation: Department of Otorhinolaryngology, Hospital de Reabilitação de Anomalias Craniofaciais, University of São Paulo, Bauru- SP. Address correspondence to: Fabiana R. Yoshimoto - Rua Manoel Pereira Rolla, nº 18-50 ap 14 - Bauru SP 17044-560
Study presented as poster at the IV Encontro Científico do HRAC-USP, in Bauru-SP, on November 10 - 11, 2001.
Article submitted on January 31, 2002. Article accepted on May 16, 2002.
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