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WhatsTheDx publishes a new Audiology case every day. Five clues, one diagnosis, and no account needed to play.
Play today's Audiology caseFive progressive clues
These are the case findings in their original reveal order, moving from the broader presentation to the most discriminating evidence.
Clue 1
A 4-year-old boy is brought to audiology by parents who have been told to wait and see for most of his life. He was referred rather than cleared at the newborn hearing screen. He has no spoken words at all, and when someone calls him from behind he does not turn.
Clue 2
The first thing you notice is not his ears. A band of pure white hair rises out of the middle of his hairline, and his mother says it was there the day he was born. There are two patches of skin — one on the upper chest, one on the left forearm — paler than everything around them, which have never tanned. Then his mother pushes her own fringe back. She has the identical white streak, she was grey by her late twenties, and her hearing is perfect.
Clue 3
Look at his face properly and it keeps going. One iris is brown and the other is blue. The inner corners of his eyes sit further apart than they should — yet measure pupil to pupil and that distance is entirely normal, so his eyes are not truly wide-set, only their inner corners are. The root of his nose is broad and the groove above his lip is short. His bowels, meanwhile, have never given a moment of trouble: meconium passed normally as a newborn, no constipation, no distended abdomen.
Clue 4
Audiometry puts a floor under it: a severe to profound loss in both ears, with bone conduction tracking air conduction all the way down and no gap between them — the cochlea, not the middle ear. High-resolution imaging of the temporal bones then declines to explain it. The cochleae are normally formed with a full complement of turns and the vestibular aqueducts are of normal calibre; there is no malformation to find. His arms are normally built, with no underdeveloped wrist bones and no missing ribs.
Diagnosis
Waardenburg Syndrome
Why the diagnosis fits
This is Waardenburg syndrome, type 1. It belongs to a group of genetic disorders caused by mutations that impair the migration and differentiation of neural crest cells, and that single embryological fact explains why a hearing clinic ends up looking at hair, skin and irises. Neural crest cells become melanocytes, and melanocytes do two apparently unrelated jobs: they colour the hair, the skin and the iris, and they populate the stria vascularis of the cochlea. Damage the lineage and you get a white forelock, hypopigmented skin patches, heterochromia irides, premature greying — and congenital sensorineural hearing loss, all from the same cause. The examination is the diagnosis here, and the scan is only there to clear the field. Four types are recognised. Type 1 carries dystopia canthorum — lateral displacement of the inner canthi — with a broad nasal root, short philtrum and short retropositioned maxilla, from PAX3 at 2q36.1, inherited autosomal dominantly, which is exactly this boy and exactly how it came from his mother. Type 2 has normally positioned canthi, heterochromia irides, and sensorineural hearing loss in about 70% of cases, from MITF at 3p13. Type 3 adds prominent musculoskeletal abnormalities such as underdeveloped carpal bones and aplasia of the first and second ribs, again from PAX3 — which is why the normal arms and ribs mattered. Type 4 resembles type 2 but adds congenital aganglionic megacolon consistent with Hirschsprung disease, from EDNRB, EDN3 or SOX10, and is autosomal recessive — which is why the entirely unremarkable bowel history mattered too. Dystopia canthorum is the feature that defines types 1 and 3 and separates them from types 2 and 4, so measuring it is not a cosmetic observation but the branch point of the classification. Diagnosis rests on clinical evaluation supported by audiograms and auditory brainstem response testing, with type 1 requiring either two major criteria or one major plus two minor criteria, and molecular genetic testing confirming the mutation. His mother, who hears perfectly, is a reminder that the same variant can express itself as nothing more than a white streak of hair.
Educational reference
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Open the clinical referenceFor education and entertainment only. This fictional case is not medical advice and does not replace supervised clinical training, diagnosis, or treatment.
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