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| An Ophthalmologic Mystery |
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Many patients with Cbl-C disease suffer from a characteristic "salt and pepper" pigmentary retinopathy with perimacular degeneration that is progressive in nature despite standard medical therapy. If retinal degeneration is caused by this particular cobalamin defect, then one would assume that either methylmalonic acid or homocysteine, which both accumulate in this disorder, are the biochemical culprits. Yet, patients that present with severe methylmalonic aciduria alone (Cbl-A, Cbl-B) or severe homocystinuria alone (Cbl-E, Cbl-G) do not develop retinal lesions. Clinicians and researchers have thus focused their attention to reduced levels of methionine as a potential casue of this rare form of retinopathy. At this time, it is not clear whether the decreased "total" level of methionine or the decreased "free" fraction of methionine plays a critical role in retinal integrity.
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Researchers believe they are on the verge of mapping the exact chromosomal location where children with Cbl-C have their genetic mutation. Armed with this information, it may be possible to develop an animal model of this rare metabolic defect, which will allow clinicians and researchers to better study the intricacies of cellular cobalamin metabolism and direct therapy in a more targeted fashion. Unfortunately, because errors in cobalamin metabolism are so rare, there is little NIH support for research that may lead to sight-saving therapeutic interventions. The Michael Clapcich Fund for Retinal Research is committed to making this type of research a reality.
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Dr. Maumenee was educated in Europe and the USA and came to Johns Hopkins in 1969. In 1972 she established the Johns Hopkins Center for Hereditary Eye Disease, a facility where patients with individually rare genetic eye diseases could obtain clinical evaluation, prognostic assessment and management. Sophisticated tests performed in Dr. Maumenee's laboratory include those for diseases such as occulocutaneous albinism, retinitis pigmentosa and other hereditary retinal dystrophies, retinoblastoma, colobomatous malformations, anterior segment malformations, storage diseases, familial retinal detachments (including Norrie disease), congenital cataracts, dislocated lenses and congenital glaucoma.
Dr. Maumenee has appointments in the Departments of Medicine (Division of Medical Genetics) and Pediatrics in addition to the Department of Ophthalmology. In 1991 she was appointed Ort Professor of Ophthalmology. She is board certified in Ophthalmology and in Medical Genetics. She has won several awards and has given numerous named and invited lectures. Dr. Maumenee is the Co- Founder and President of the International Society for Genetic Eye Diseases and is the President of the Ocular Genetics Study Club. She is the author of many scientific articles and has edited several books on the genetics of eye diseases. Her clinical and research interests are the nosology and management of hereditary ocular diseases, population genetics, computer application to genetic analysis and molecular genetics.
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