A 17-year-old male patient was admitted because of progressive hearing loss
since the age of six. His former blood and radiology investigation had rev
ealed idiopathic hyperphosphatasia. On ENT examination bilateral thickened
tympanic membranes with severe mixed-type hearing loss was diagnosed. Compu
terized tomography (CT) demonstrated expansion of the calvarial bones, incl
uding the temporal bones, except for the otic capsule. Middle-ear explorati
on revealed thickened middle-ear mucosa and a stone hard, immobile bony mas
s instead of the normal ossicular chain at the posterior superior part of t
he mesotympanum. No ossicular reconstruction could be attempted and the pat
ient was rehabilitated with a hearing aid.