Article
Ocular ochronosis (Alkaptonury): globe rupture after blunt trauma
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Published: | September 22, 2004 |
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Outline
Text
Methods
A 78-year-old man presented in our outpatient department after blunt trauma to his right globe. He was pseudophakic in both eyes and in his history he mentioned a primary open-angle glaucoma. In his anterior eye segment well-known dark-brown pigmentation occured with no change of size within the last years (diagnosis: melanosis conjunctivae et sclerae). Further history revealed M. Bechterew and renal stones. The patient reported, that during his last knee joint operation something "special" was noticed. Ophthalmologic examination revealed following findings: VA R: Hand movements, L sc:0,8; IOP R 0 mmHg, L 18 mmHg. Anterior eye segment: Conjunctiva with hyposphagma, Cornea clear/ smooth/ reflecting, complete hyphaema. L Pseudophakia, dark brown scleral pigmentation before the insertions of the recti. Fundus examination R: not possible. L: without further pathological findings. Sonography: Expected scleral perforation. During operation, the IOL was found under the conjunctiva. Scleral rupture was found at the insertion of the m. rectus medialis. The brown plaque-like area was ruptured as well. Clinical course: After IOL removal and suturing the globe remained intact. Visual acuity was restored by a contact lens.
Results
Microscopic findings of the brownish pigmentation: Normal conjunctival epithelium, extracellular brown plaque-like structures similar to pigmentations. These pigmentations varied in size and were found most often next to vessels. On a second look the patient showed remarkable brown skin colour and very dark ears.
Conclusions
This patient showed all the classical hallmarks of alkaptonuria: This disease is due to a misfunction of the phenylalanin metabolism. Accumulation of homgentisinic acid occurs due to a defect of homogentsiacid-1,2-dioygenase. Within the pathway another enzymes creates a chinoid pigment which diffuse into collagenous tissue. Vessels, cartilage and the sclera are affected most often. Cartilage appears dark brown to black, which may have wondered the surgeons before. Homogentisinic acid is washed out by the kidney as well, oxidation of the urin makes the urine look dark (hence the classic "dark spots" in the underwear). Several gene loci have been discribed. The disease is transmitted autosomal recessive. No therapeutic concepts are available. Although the patient showed all classic stigmata of alkaptonuria, he was photographed every year in our clinic, documenting the "melanosis". A careful history and good clinical examination apart from the slit-lamp would have led to the right diagnosis. Alkaptonuria belongs to the differential diagnosis of all pigmentation disorders of the conjunctiva and sclera.