Case Study An infant boy though apparently healthy at birth

Case Study: An infant boy, though apparently healthy at birth, displays failure to thrive and episodes of vomiting. The pregnancy was unremarkable. At 8 months the child is underweight, has small muscle mass, inability to hold head steady, and fatigues easily. The child is also displaying significant development delays. Laboratory results show persistent metabolic acidosos (pH 7-7.2, normal is 7.36-7.44), evelated blood lactic acid (9mmol/L, normal is 1-2 mmol/L), and blood pyruvate levels were also elevated. The patient was put on a diet severly restricted in carbohydrates and showed some improvment.

Question: Why are blood lactic acide levels high? Where did the lactic acid come from?

Solution

Laboratory results showing low pH value compared to normal is due to increased blood level of lactic acid. Lactic acid is produced in muscle cells during hypoxia (low oxygen availability) condition and during excessive exercise. The child seems to suffering from metabolic disorder. In normal conditions, pyruvate produced as a result of glycolysis (Glucose breakdown pathway which is used further for energy production) is further utilized in tricarboxylic acid cycle (TCA) for energy production. The key enzyme involved in routing pyruvate to TCA cycle is pyruvate dehydrogenase complex. The non-availability of this enzyme leads to routing of pyruvate to anaerobic glucose catabolism which leads to production of lactic acid and lesser energy compared to normal pathway.