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PubMed1984

[Involvement of the tympanic membrane and ear ossicle system in ochronotic alkaptonuria].

Ochronotic alcaptonuria is a rare hereditary disease in which the metabolism of phenylalanine and tyrosine is disturbed, leading to accumulation and urinary excretion of homogentisic acid. Its affinity towards bradytroph tissues makes e.g. cartilage, tendons, sclera etc. become stained dark, hard and inflexible, leading to early arthrosis or ruptures of tendons. In the ENT literature mostly signs like darkening of the conchas, the septum or the larynx are mentioned, whereas involvements of the middle ear are rarely described. Such changes were seen in a 60-year old patient, who showed dark discolourations of his thickened tympanic membranes. He had a combined high-frequency hearing loss, the conductive component of which we explain as an increase of mass and changed elasticity. It may also be due to alterations of the ossicular chain. The case was demonstrated to direct the ENT specialist's attention to findings suspicious of ochronotic alcaptonuria and - on the other hand - to present photos of involved tympanic membranes, which in this kind we did not see in the literature.

Alkaptonuria↗
PubMedDate not supplied

[Biomechanical studies on the pathogenesis of ochronotic arthropathy].

The enzymatic defect leading to alcaptonuria is well known. However, the pathogenesis of the associated arthropathy is poorly understood. From clinical and morphological observations it is assumed that the breakdown of ochronotic cartilage is due to an increased fragility. To test the hypothesis that polymerisation products of homogentisic acid change the biomechanical behaviour of hyalin cartilage, investigations on natural ochronotic cartilage and tissues following in vitro incubation with homogentisic acid were performed. It could be demonstrated that the "ochronotic situation" is associated with an increased hardness and a decreased elasticity of the hyalin cartilage. For the pathogenesis of ochronotic arthropathy it is assumed that these alterations, in association with mechanical stress to the joints, lead to cartilage destruction.

Adolescent↗