LAUSR

Case report A 13 month-old baby girl presented with vomiting and refusal to feed; she was mostly breast feeding. On examination, she appeared off form, underweight, hypotonic and pale. Bedside testing revealed a low blood glucose level of 1.7 mmol/l with a normal lactate. She was also noted to have mild electrolyte disturbances and a slightly acidotic venous blood gas analysis. Further investigations, including urinary organic acids, revealed marked ketonuria with increased methylmalonic acid (MMA) (1014 µM/mmol creat., ref. <8) and orotic acid excretion. She was found to be severely deficient in vitamin B12 (<125 ng/l) which explained her macrocytic anaemia and raised plasma homocysteine (62 microM/l, ref. <8) and urinary MMA. Her initial plasma amino acids showed relatively increased glutamine, low citrulline and arginine with other amino acids relatively low. Plasma ammonia levels were essentially normal. Interventions/Results The patient was initially commenced on intravenous fluids with dextrose and electrolytes. She was also treated with parenteral vitamin B12 injections, along with folate supplements, which caused a marked improvement in mood, tone, and appetite. MMA excretion, homocysteine and blood film normalized although excretion of orotic acid persisted. Further investigations revealed that her mother had low vitamin B12 levels and was positive for parietal cell antibodies, indicative of maternal pernicious anemia. Metabolic work-up also included an Allopurinol load test which was abnormal. Ornithine transcarbamylase (OTC) gene mutation analysis did not detect any pathogenic variants. Although orotic aciduria has a recognized association with megaloblastic anemia, it would not be explained by low serum B12 levels. The family was instructed that their child could still become unwell and would need monitoring and/or dietetic intervention and an emergency regime during periods with increased metabolic stress, such as infections. The girl made a full recovery with no active issues identifiable at 2 y of age. Conclusion This case report highlights the following points 1) the importance of glucose and ketone measurements along with a full hypoglycemia work up at the point of care, if glucose low, in a child who presents acutely unwell e.g. with poor feeding and vomiting, 2) one should be vigilant for potential maternal causes in an infant especially those who are breastfed, and 3) the potential relevance and diagnostic dilemma caused by incidental findings of yet uncertain significance for this individual.