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A. Dharmasena, A.R. Kerr; Ocular Manifestations of Inherited Lack of Serum Transcobalamin ll: A Case Report . Invest. Ophthalmol. Vis. Sci. 2006;47(13):2025.
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Trancobalamin II (TCII), a plasma globulin, is the primary transport protein for Vitamin B12 (Vit B12) in the blood. Absence of TC II leads to severe megaloblastic anemia in early infancy in spite of normal Vit B12 levels in blood. This very rare disorder of intracellular Vit B12 deficiency shows an autosomal recessive inheritance. Only a few case reports which address the ocular manifestations are available in literature. Purpose of this paper is to describe the course of ophthalmic manifestations in a patient, now aged 47 years, who had suffered the effects of this inherited lack of TCII since 9days of age.
A case report
9 days after a normal birth to nonconsanguineous parents of Irish/English descent, he was presented with vomiting,diarrhea, spontaneous bleeding and hypotension. Blood film and bone marrow biopsy was grossly megaloblastic. He was treated with repeated blood transfusions, Vit B12 and Folic acid supplements. Walking was delayed due to unsteady gait. He started to develop status epilepticus at 2 ½ years and showed a poor response to antiepileptics but showed a dramatic response to B12 injections. At 17 years, seizures continued with slurred speech and ataxia. Extensive investigations revealed an intracellular deficiency of Vit B12, due to TC II deficiency. TC II was absent in the patient, reduced in the mother and uncle and normal in his sister. Diagnosis of Inherited TC II deficiency was confirmed. Intramuscular Vit B12 (5000µg) injections 3 times a week with anticonvulsants started. He was extremely well since then apart from mild learning difficulties (IQ 60). At 29 years, he was referred to us due to inability to improve the vision beyond 6/12 of Snellen’s chart. Near vision was N5. A uniform granular horse–shoe shape hypopigmentation surrounding the macula, minimally affecting the retinal pigment epithelium under the papillomacular bundle, was noticed at fundoscopic examination. However, there were no salt–and–pepper or bone–spicule pigment changes at the posterior pole. In spite of regular administration of megadose B12 injections, atrophic maculopathy and visual acuity deteriorated. At the age of 45, best corrected visual acuity dropped to 6/24 in both eyes, and binocular acuity to 6/18 and he is registered partially blind.
Only a very few cases of retinal dystrophy associated with congenital TCII deficiency has been reported. In spite of maintenance of serum Vitamin B12 levels by regular injections, macular degeneration progressed in this case. In previous literature the patients who received similar treatment did not show further deterioration.
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