| Abstrakt: |
The cobalamin C (cbl C) complementation group of combined MMA/HCYS is the most common o f the inborn errors of vitamin B12 metabolism, affecting both methylmalonyl-CoA and homocysteine (Hcys) degradation. We have recently diagnosed 2 patients with this disorder. AH. a 3 week old male, presented with lethargy, decreased oral intake, dehydration and pancytopenia. There had been a preceding upper respiratory infection. Parents were first-cousin Saudi Arabians. VM, a Hispanic female, presented at 19 days of life with lethargy. hyptonicity, dehydration, cough, decreased oral intake, significant thrombocytopenia, and mild pancytopenia. For both, worsening neurologic status was accompanied by seizures, and sepsis was suspected followed by appropriate intervention. Subsequent metabolic work-up revealed MMAIHCYS; fibroblast analysis for AH verified the cbl C complementation subgroup (Dr. D. Rosenblatt, Montreal, Canada; studies in VM are pending, although she likely falls within the same subgroup). Plasma total Hcys remains persistently elevated in AH (26-39 uM, n=8; nl < 10) and was 216 uM for VM (n=l). CSF total Hcys was 35 uM for VM (nl < 0.08). We conclude that I) diagnosis of patients with MMA/HCYS of the cbl C complementation subgroup may be hampered by absence of acute metabolic derangement (acidosis, hyperammonemia, hypoglycemia, ketosis) combined with features (lethargy, obtundation) suggesting sepsis; and 2) significantly increased CSF Hcys may be the underlying cause of altered neurologic status in these patients. |
