Elevated hydroxy acylcarnitines in a carrier of LCHAD deficiency
during acute liver disease of pregnancy - A common feature of the pregnancy complication?
Two biochemical phenotypes of defects concerning the MTP complex have been described: isolated LCHAD deficiency and generalized MTP deficiency, with decreased activities of all 3 enzymes.
LCHAD deficiency is the most common defect of the MTP complex, and hundreds of cases have been identified.
Accumulation of 3-hydroxy-fatty acids in the culture medium of long-chain L-3-hydroxyacyl CoA dehydrogenase and mitochondrial trifunctional protein deficient skin fibroblasts: Implications for medium chain triglyceride dietary treatment of LCHAD deficiency
. Pediatr Res 2003;53:783-7.
C160H, detected at m/z 472, is one of several long-chain hydroxyacylcarnitines present in significantly increased concentrations in both trifunctional protein (TFP) and LCHAD deficiency
. LCHAD and TFP deficiencies are indistinguishable by acylcarnitine profile alone (110, 111), although molecular analysis is available for the most common LCHAD mutation.
In LCHAD deficiency
, there was a marked increase of 3-OHFAs of chain lengths 3-OH-C14 and -C16 and an increase in 3-OH-C18.
Since the first description of LCHAD deficiency in 1991, LCHAD- or MTFP-deficient individuals have been diagnosed with increasing frequency and with a wide array of symptoms.
This finding suggests that in systems that assay cell culture media, our assay may be a more useful tool for diagnosing LCHAD deficiency than for measuring acylcarnitines in these cells.
In LCHAD deficiency, there is a marked increase in 3-OH-FAs of chain lengths [C.sub.14] and [C.sub.16], whereas in SCHAD deficiency, the medium chain 3-OH-FAs, [C.sub.6] to [C.sub.10], predominate, with a [3-OH-C.sub.8] concentration higher than the [3-OH-C.sub.6] concentration and normal excretion of [3-OH-C.sub.14] and [3-OH-C.sub.16].
Because the assay only measures increased concentrations of the intermediates of the [beta]-oxidation pathway, however, it does not distinguish between true LCHAD deficiency and TFP deficiency, in which all three of the enzymes that make up the TFP are affected.
It also has ramifications for the mother during subsequent pregnancies because LCHAD deficiency in the fetus has been associated with a severe obstetric complication, acute fatty liver of pregnancy [151.
However, the frequency of this mutation is considerably less than the A985 [right arrow] G mutation in medium-chain acyl-CoA dehydrogenase deficiency; thus, screening for the G1528 [right arrow] C mutation alone will result in considerable underdiagnosis of LCHAD deficiency.