"Ant-egg" cataract revisited.
OBJECTIVE
Hereditary congenital cataract varies immensely concerning location and form of the lens opacities. A specific and very rare phenotype is called "ant-egg" cataract first described in 1900. "Ant-eggs" have previously been examined using light microscopy, backscattered electron imaging and X-ray scans and electron microscopy. The purpose of this study was to further characterize "ant-egg" cataract using modern technology and display the history of the "ant-eggs" after cataract extraction.


METHODS
"Ant-eggs" were examined using Heidelberg SPECTRALIS Optical Coherence Tomography (OCT)(Heidelberg Engineering, Heidelberg, Germany). Ten "ant-eggs" were extracted; four of these as well as control tissue were analyzed by mass spectrometry (AB Sciex). Proteins were identified and their approximate abundances were determined. Immunohistochemical staining was carried out on the remaining "ant-eggs" for cytokeratin and S100.


RESULTS
In anterior OCT-images, the "ant-egg" structures are localized on the iris. Comparative pictures showed that they stayed in the same location for more than 45 years. Mass spectrometry of "ant-eggs" yielded a proteome of 56 different proteins. Eighteen of the 56 "ant-egg" proteins (32 %) were neither present in our controls nor in a known fetal lens proteome. Among these were cytokeratin and Matrix-Gla protein. Immunohistochemical reactions were positive for cytokeratin and S100.


CONCLUSIONS
This study demonstrates the previously unknown protein composition of the "ant-egg" structures in "ant-egg" cataract. Eighteen of these proteins are not natively found in the human lens. Moreover, "ant-eggs" do not vary over time, after cataract extraction, regarding size and location.
Department of Ophthalmology, Aarhus University Hospital, 8000, Aarhus, Denmark. Kaare.clemmensen@gmail.com.
Kåre
http://orcid.org/0000-0003-4418-967X
K
Clemmensen
Department of Molecular Biology and Genetics, Science Park, Aarhus University, Aarhus, Denmark.
Jan J
JJ
Enghild
Department of Ophthalmology, Aarhus University Hospital, 8000, Aarhus, Denmark.
Anders
A
Ivarsen
Department of Ophthalmology, Innland Hospital, Lillehammer, Norway.
Ruth
R
Riise
Department of Ophthalmology, Aalborg University Hospital, Aalborg, Denmark.|Department of Clinical Medicine, Aalborg University, Aalborg, Denmark.
Henrik
H
Vorum
Department of Pathology, Rigshospitalet, University of Copenhagen, Copenhagen, Denmark.|Department of Ophthalmology, Rigshospitalet, University of Copenhagen, Copenhagen, Denmark.
Steffen
S
Heegaard
D002386:Cataract / Q000151:congenital* / Q000175:diagnosis / Q000378:metabolism; D002387:Cataract Extraction; D005136:Eye Proteins / Q000032:analysis*; D006801:Humans; D007908:Lens, Crystalline / Q000378:metabolism*; D013058:Mass Spectrometry; D008875:Middle Aged; D041623:Tomography, Optical Coherence / Q000379:methods
D005136:Eye Proteins
Anterior OCT; Congenital cataract; Connexin46; Hereditary; Histology; Mass spectonometry; Proteome