Metabolism
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Muscle weakness, heart failure and profound hypoglycaemia in a young girl
CUD is a 7 year old girl. Since early infancy she has suffered from occasional attacks of coma, especially when she has been suffering from one of the usual childhood feverish illnesses. She tires easily, and has never been able to undertake strenuous exercise, or keep up with her peers in the playground.
Six months ago she complained of chest pains, and a physical examination was suggestive of heart failure, with tachycardia, moderate mitral insufficiency, gallop rhythm and left ventricular heave. A two dimensional echocardiogram showed the left ventricular end-diastolic dimension to be elevated at 7.46 cm, with a fractional shortening of 15%. A chest X-ray showed moderate enlargement of her heart. Her liver was moderately enlarged and palpable.
A fasting blood sample taken when she was first admitted to hospital gave the following results:
CUD |
reference range |
|
| glucose (mmol /L) | 2.6 |
3.8 - 6.0 |
| non-esterified fatty acids (mmol /L) | 1.8 |
1.0 - 1.4 |
| ketone bodies (mmol /L) | not detectable |
2.0 - 3.0 |
| sodium (mmol /L) | 141 |
135 - 145 |
| potassium (mmol /L) | 4.1 |
3.6 - 5.0 |
| bicarbonate (mmol /L) | 20 |
18 - 23 |
| ammonium (µmol /L) | 60 |
< 50 |
| pH | 7.4 |
7.35 - 7.45 |
| insulin (µU /mL) | 3.8 |
4 - 5 |
| glucagon (pg /mL) | 190 |
160 - 180 |
| aspartate aminotransferase (units /L) | 55 |
< 31 |
| alanine aminotransferase (units /L) | 64 |
< 31 |
| creatine kinase - muscle isoenzyme (units /L) | 366 |
< 170 |
| lactate dehydrogenase (units /L) | 250 |
< 290 |
| alkaline phosphatase (units /L) | 300 |
< 150 |
| gamma-glutamyl transpeptidase (units /L) | 290 |
< 60 |
| total carnitine (µmol /L) | 5.1 |
40 - 60 |
What conclusions can you draw from these results?
She is slightly hypoglycaemic, and her non-esterified fatty acids are slightly higher than would be expected for an overnight fast. The lack of detectable ketone bodies is interesting and will bear further investigation. Her plasma concentrations of insulin and glucagon are appropriate for her mild hypoglycaemia. Her plasma ammonium concentration is somewhat higher than normal.
The elevated activities of aspartate and alanine transaminases, alkaline phosphatase and gamma-glutamyl transpeptidase are all suggestive of liver disease or damage.
The elevated activity of creatine kinase is suggestive of muscle damage - either skeletal or cardiac muscle, but the high normal activity of lactate dehydrogenase suggests that there has not been any recent death of cardiac muscle cells.
The abnormally low serum concentration of carnitine is interesting.
Carnitine
is both synthesised in the body and also obtained the diet. This means that
dietary carnitine deficiency is unlikely, and indeed strict vegetarians, who
have negligible dietary sources of carnitine are still able to maintain a normal
plasma concentration.
A urine sample showed that she excreted very much more carnitine than children of her age, and most of this was as free carnitine, not fatty acid esters of carnitine (acyl carnitine).
Her renal clearance of carnitine (both free and esterified) was almost the same as that of creatinine, whereas normally the renal clearance of free carnitine is only about 2% of that of creatinine (although esterified carnitine has a higher renal clearance than free carnitine).