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Abstract
Less than 20% of cblC cases that have been reported in literature were late onset, and none presented with manic-depressive psychosis at onset. [...]sibling cases of cblC disease through autosomal recessive inheritance were rare. Physical examination showed that the muscular strength in both lower extremities was Level IV with hyperreflexia of bilateral patellar tendons and a suspicious positive Babinski sign on the left side. Six months previously, he presented with bilateral visual decline, cognitive impairment, and depressive symptoms, similar to his brother. Both patients had undergone magnetic resonance imaging (MRI) examination of the spinal cord in their local hospital, and the results were normal, whereas brain MRI showed mild diffuse atrophy of the cerebral cortex in both patients. Ocular fundus examination demonstrated bilateral optic atrophy in both patients and pigmentary retinal degeneration in the left eye of the elder brother. Gas chromatography-mass spectrometry (GS/MS) and tandem mass spectrometry (MS/MS) analyses revealed significantly elevated methylmalonic acid in urine and homocysteine (Hcy) levels in the plasma, and a reduced methionine level in the plasma [Table 1]. {Table 1} The methylenetetrahydrofolate reductase gene (MTHFR) analysis identified a heterozygous C>T mutation in the younger brother and a homozygous C>T mutation in the elder brother. After the diagnosis of cblC disease was made, antipsychotic drugs were discontinued and the patients were treated with levocarnitine (intravenous injection, 1 g/d), MeCbl (intramuscular injection, 1 mg/d), folic acid (oral, 5 mg/d), and Vitamin B6 (oral, 30 mg/d). Among them, five pairs were identified as the late-onset cblC type,...