Prevalence and long-term course of macro-aspartate aminotransferase in children

Macroenzymes as a reason for aminotransferases flare in cystic fibrosis patients on CFTR modulators therapy - Report of three cases

It has been shown that macro-ALT/macro-AST cause false increase of ALT/AST activity in standard laboratory testing. This short communication presents a group of cystic fibrosis subjects who developed aminotranferases flare a few months after initiation of CFTR modulators therapy. Patients did not present any clinical signs or symptoms of liver failure and differential examination did not show any underlying liver disease. All patients tested positive for macro-ALT and macro-AST. Despite increased and fluctuating ALT/AST activity in standard tests patients restarted CFTR modulators therapy with good clinical effect and do not present any other than hypertransaminasemia signs or symptoms of progressing liver disease. Our data shows that ALT/AST flare during CFTR modulators therapy may be related to macro-ALT/macro-AST, thus patients with high ALT/AST during CFTR modulators therapy should be tested for macro-ALT/macro-AST.

Persistently high serum aspartate aminotransferase level in an asymptomatic young patient

Key Clinical Message

We report a young man with isolated elevated AST. He had no other evidence of liver or other related diseases. All the tests and examination reports were negative. The final diagnosis of macro-AST was confirmed by PEG precipitation tests.

Abstract

Elevated liver enzymes, such as alanine aminotransferase (ALT) and aspartate aminotransferase (AST), may commonly indicate liver injury. However, macro-AST is generally a benign condition that may be considered as pathologic by clinicians. A young man with isolated elevated AST for more than 10 years who have taken extensive tests and examinations was diagnosed with macro-AST in our article. Thus, in patients with isolated AST-elevation, polyethylene glycol (PEG) precipitation test was recommended to test whether macro-AST could be diagnosed.

[Clinical, biochemical and epidemiological features of macro-AST preceding inflammatory bowel disease diagnosis by several years]

INTRODUCTION

An isolated elevation of aspartate aminotransferase (AST) is a diagnostic issue. Macro-aspartate aminotransferase (macro-AST) corresponds to the formation of complexes between AST and immunoglobulins.

CASE REPORT

We report the case of a patient with macro-AST identified several years before the onset of inflammatory bowel disease (IBD). A 6-year retrospective analysis in our laboratory identified only one case out of 42 540 adult patients.

CONCLUSION

The objective of this work is to increase awareness of this benign disorder among clinicians and biologists, as well as to aid in prescribing only the required tests.

The significance of isolated aspartate aminotransferase elevation in healthy paediatric patients

AIM

Aspartate aminotransferase (AST) is an enzyme expressed in several organs; therefore, AST elevation may reflect outside of liver pathology. AST elevation may also be associated with macro-AST (m-AST). The aim of this study was to evaluate the long-term course of children with prolonged isolated AST elevation and the prevalence of m-AST in our cohort.

METHODS

We retrospectively reviewed the medical charts of children diagnosed with prolonged isolated AST elevation and were evaluated for m-AST.

RESULTS

Thirty-two patients were included. AST elevation persisted for a median of 66.6 months and ranged from 1.23 to 12-fold upper limit of normal (ULN). Twenty-two percent were m-AST positive and 44% had borderline levels of m-AST. A statistically significant difference was found for age at presentation between the borderline and the positive m-AST groups (31 vs. 69 months, respectively. p = 0.045). None of the patients with elevated AST developed significant liver disease.

CONCLUSION

We confirm the benign course of prolonged isolated AST elevation in general and m-AST in particular. A fifth of the patients with isolated AST elevation were m-AST positive. No differences have been found in AST levels between negative, borderline or positive m-AST.

Importance Of Laboratory Detection Of Macro-Aspartate Aminotransferase

The macroenzyme form of aspartate aminotransferase (macro-AST) is formed by the binding of AST with immunoglobulins. Macro-AST excretion from serum is prolonged because of its high molecular weight, leading to increased AST activities. Because of the difficulty in detecting macro-AST through routine laboratory tests, affected patients often undergo repeated examinations, with associated anxiety. We report a case in which macro-AST was detected by assaying the patient’s serum after refrigeration at 4ºC for 3 days. The sample showed progressive loss of AST activity compared with that frozen in the refrigerator, indicating the presence of macro-AST, which was confirmed as a complex with IgG-κ. The cold storage method was validated using many samples obtained from several patients. Use of this simple method to detect macro-AST may avoid unnecessary examinations and patient anxiety even at primary care facilities.

Persistent elevation of aspartate aminotransferase in a child after incomplete Kawasaki disease: a case report and literature review

Background

Interpretation of abnormalities in liver function tests, especially in asymptomatic children, is a common problem faced by clinicians. Isolated elevation of aspartate aminotransferase may further puzzle physicians. Macro-aspartate aminotransferase (AST) results from complexes AST produces with other plasma components, such as immunoglobulin. To our knowledge, this is the first report on a case of macro-AST-associated incomplete Kawasaki disease (KD). It is to make physicians aware of this benign condition and help to prevent extensive, unnecessary investigations and invasive workups.

Case presentation

A 16-month old boy with a 7-day history of fever was admitted to our pediatric ward for pyrexia workup. After complete investigations, KD was confirmed by a pediatric rheumatologist. During his admission and serial follow-up tests, an isolated AST elevation was noted. Comprehensive tests were performed and using the polyethylene glycol (PEG) precipitation method, macro-AST was confirmed. The patient has been followed up for 3 years, and so far, the benign nature of this condition has been confirmed.

Conclusion

Clinicians should consider testing for macro-AST when elevated AST is the only abnormal lab finding. Although an uncommon finding, macro-AST may be seen in both children and adults. There are many reasons for this phenomenon, including resolved acute hepatitis or in some cases, inflammatory bowel disease, hepatic malignancy, monoclonal gammapathy, celiac disease, or KD; however, it may be observed in asymptomatic healthy children as well. Using the PEG precipitation method, a definitive diagnosis can be made. In none of these conditions does macro-AST have any prognostic significance. An appreciation of macro-AST may prevent the need for more invasive investigations to which patients may be unnecessarily subjected. It is important to recognize this condition as benign and assure patients that no specific treatment is required.

Isolated elevated aspartate aminotransferase in an asymptomatic woman due to macro-aspartate aminotransferase: A case report

BACKGROUND

Macro-aspartate aminotransferase (AST), a macroenzyme, is a high-molecular mass complex formed by self-polymerization or association with other serum components that are difficult for the kidney to clear, leading to the isolated elevation of serum AST activity. Cases of macro-AST formation are rare, with only 3 published in the English language literature up to September 2019 in China. In this paper, we present a case in which an asymptomatic woman with persistent isolated elevated AST was confirmed as having macro-AST by the polyethylene glycol precipitation method.

CASE SUMMARY

A 34-year-old woman was referred to our clinic for elevated AST levels with normal levels of other liver-associated enzymes on November 12, 2018. Her AST level of liver function test had been abnormal for 7 mo before she came to the clinic. The patient was asymptomatic with a normal physical examination. There was no relevant family history and no alcohol consumption or smoking. She had a several-month history of traditional Chinese medical taking and had stopped it 1 year prior. The laboratory tests in our clinic showed only the elevation of AST (89.5 U/L) with no other significant abnormalities. We performed the precipitation technique with polyethylene glycol to confirm the presence of macro-AST. Then for almost a year, her AST level still fluctuated in the abnormal range.

CONCLUSION

This case highlights that clinical physicians should be familiar with this rare condition of persistent isolated AST elevation due to the presence of macro-AST to avoid unnecessary investigation and patient anxiety.

A heterozygous mutation in GOT1 is associated with familial macro-aspartate aminotransferase

BACKGROUND & AIMS

Macro-aspartate aminotransferase (macro-AST) manifests as a persistent elevation of AST levels, because of association of the protein with immunoglobulins in the circulation. Macro-AST is a rare, benign condition without a previously confirmed genetic basis.

METHODS

Whole exome sequencing (WES)-based screening was performed on 32 participants with suspected familial macro-AST, while validation of variants was performed on an extended cohort of 92 probands and 1,644 healthy controls using Taqman genotyping.

RESULTS

A missense variant (p.Gln208Glu, rs374966349) in glutamate oxaloacetate transaminase 1 (GOT1) was found, as a putative causal variant predisposing to familial macro-AST. The GOT1 p.Gln208Glu mutation was detected in 50 (54.3%) of 92 probands from 20 of 29 (69%) families, while its prevalence in healthy controls was only 0.18%. In silico analysis demonstrated that the amino acid at this position is not conserved among different species and that, functionally, a negatively charged glutamate on the GOT1 surface could strongly anchor serum immunoglobulins.

CONCLUSIONS

Our data highlight that testing for the p.Gln208Glu genetic variant may be useful in diagnosis of macro-AST.

LAY SUMMARY

Higher than normal levels of aspartate aminotransferase (AST) in the bloodstream may be a sign of a health problem. Individuals with macro-AST have elevated blood AST levels, without ongoing disease and often undergo unnecessary medical tests before the diagnosis of macro-AST is established. We found a genetic variant in the GOT1 gene associated with macro-AST. Genetic testing for this variant may aid diagnosis of macro-AST.

Distribution of serum concentrations reported for macroenzyme aspartate aminotransferase (macro-AST)

Background

The presence of macroenzyme (M) is often the explanation of an isolated elevation of aspartate aminotransferase (AST). Where M is identified, it is reasonable for the clinician to ask where an individual patient's result fits in with known concentrations of M. In this context, we conducted a survey of literature to examine the distribution of reported serum concentrations of macro-AST. We also analyzed the distribution data to examine whether elevations were consistent with simple alteration of circulatory half-life (t_1/2) of M relative to normal AST.

Methods

Distributions of M were compiled from the literature. These distributions were compared to predictions based on fixed changes in t_1/2 applied to the reference interval for AST.

Results

There was a bimodal distribution of literature values for M (n =51), comprised roughly of populations A (M <200 U/L; 60% of total) and B (M >200 U/L; 40% of total). The two distributions were reasonably well characterized by a simple projection to the right of the reference interval for AST according to increased t_1/2 (A: t_1/2 =3.3 days; B: t_1/2 =19.8 days) relative to AST (t_1/2 =0.7 days).

Conclusions

Knowledge of distributions for M may be useful in discussion with clinicians regarding significance of M for individual patients. Distributions for M were consistent with the simplest explanation for elevated AST due strictly to an extended circulatory lifetime for M. Caveats to analysis, however, include selection within literature data mainly for patients with various co-morbidities.

[Macro-AST and myeloma: An incidental association?]

INTRODUCTION

Macro-AST is recognized as a classical aetiology of isolated and persistent increase of serum aspartate aminotransferase (AST) levels. Macro-AST are high molecular weight complexes associating AST and a macromolecule, often an immunoglobulin. Although those macroenzymes of unknown pathogenesis are usually non-pathogenic, association with several diseases, including autoimmune diseases and liver diseases has been described.

CASE REPORT

We report here the case of a 45-year-old patient with previously normal liver enzymes in whom an AST elevation and an IgA monoclonal gammopathy were discovered concomitantly. Following the diagnosis of multiple myeloma, we could evidence in the patient's serum a complex between AST and the monoclonal IgA. AST levels course followed closely the progression of monoclonal gammopathy.

CONCLUSION

This is the first report demonstrating a clear link between macro-AST and a monoclonal gammopathy.

A comparison of methods for evaluation of a case of suspected macro-aspartate aminotransferase

BACKGROUND

Macro-aspartate aminotransferase (macroAST) is a high molecular weight form of AST that is usually formed through association with immunoglobulin (Ig) in the circulation. As a result of reduced inactivation, clearance or excretion, AST values are persistently increased. This can lead to problems interpreting these values and diagnosing the patient, especially if clinicians are not aware of this phenomenon.

METHODS

For a case of suspected macroAST, we compared three simple methods: polyethylene glycol precipitation, ultrafiltration, and Ig depletion using protein A and G.

RESULTS

All three methods were consistent with a diagnosis of macroAST.

CONCLUSIONS

The protein A and G method was straightforward and provided unambiguous results. However, given the affinity of protein A and protein G, it likely only detects AST-IgG macrocomplexes.

[Isolated aspartate aminotransferase elevation in a young, healthy person. Case report]

The authors present diagnostic methods used in a young healthy person who had isolated aspartate aminotransferase elevation. Polyethylene glycol precipitation test, aspartate aminotransferase serum electrophoresis and immunofixation were performed for measuring the macro-aspartate aminotransferase. It was found that aspartate aminotransferase activity in the patient was almost completely eliminated after precipitation of immunoglobulins with polyethylene glycol. In addition, aspartate aminotransferase migrated in the control samples to the anode while in the patient towards the cathode. Finally, a wider and more intense staining band was visible in the region of immunoglobulin A in the patient sample on the immunofixation gel as compared to the control sample. The authors conclude that that increased aspartate aminotransferase activity was due to macro formation. The elevated level of immunoglobulin A and selective increase of polyclonal immunoglobulin A (κ and λ light chains) indicated that the macro format was created by immunoglobulin A bound to aspartate aminotransferase.

A practical approach to the child with abnormal liver tests

The presence of elevated aminotransferases on routine blood tests can reveal liver diseases of various severities. In children, etiologies are more numerous and complex than those usually considered in adults. Information derived from family and personal history, physical examination and basic laboratory data are necessary to reach a timely and correct diagnosis. A stepwise approach is proposed to guide the timing of more specific investigations that are often required.

Fatty liver disease and hypertransaminasemia hiding the association of clinically silent Duchenne muscular dystrophy and hereditary fructose intolerance

We report a case with the association of well self-compensated hereditary fructose intolerance and still poorly symptomatic Duchenne type muscular dystrophy. This case illustrates the problems of a correct diagnosis in sub-clinical patients presenting with “cryptogenic” hypertransaminasemia.

Aminotransferases and muscular diseases: a disregarded lesson. Case reports and review of the literature

The aim of this study was to call the attention to the often disregarded message that hypertransaminasemia may be a marker of both liver and muscle diseases by presenting personal case reports and a systematic literature review. Three male children (mean age 5.7 years) were inappropriately addressed, during the last 12 months, to our paediatric liver unit for diagnostic work-up of a chronic hypertransaminasemia of unknown origin. In one of them, a liver biopsy had already been performed. On admission, physical examination, evaluation of serum levels of creatine kinase, and dystrophin genetic testing finally led to a diagnosis of muscular dystrophy. One hundred fourteen similar cases, 21 with unnecessary liver biopsy, were found by Medline search. Expensive and invasive tests planned to investigate liver diseases should be postponed until alternative sources of increased serum aminotransferases, primarily myopathic injury, have been excluded.

Macro-AST: misleading finding in an adolescent with MCAD-deficiency

Background

MCAD-deficiency is the most common inborn error of fatty acid oxidation now included in many newborn screening programms using MS/MS. During prolonged catabolic episodes, patients may suffer from metabolic decompensation with dysfunction of liver, skeletal- and heart muscle as well as brain. In anabolism, neither clinical symptoms nor biochemical signs of organ dysfunction occur.

Case presentation

We report a female patient with MCAD-deficiency in whom at the age of 11 years isolated AST-elevation was found without any clinical or biochemical signs of organ dysfunction. We showed by polyethylene glycol precipitation that macro-AST formation was responsible for this biochemical finding. AST was probably complexed with immunoglobulins possibly related to an allergic disposition. Macro-AST formation is not a special feature of MCAD-deficiency but rather a non-specific, coincidental finding which also occurs in healthy individuals. The general practitioner consulted by the patient before coming to our outpatient clinic for inborn errors of metabolism was worried that isolated AST-elevation indicated cell damage in MCAD-deficiency. He ordered further diagnostic tests like ultrasound, ECG and echocardiography without any pathology.

Conclusion

In isolated AST-elevation, macro-AST has to be considered in order to avoid unnecessary, costly and invasive evaluation. This is not only true for healthy persons but for patients with chronic diseases like MCAD as well.

Laboratory detection of macro-aspartate aminotransferase: case report and evaluation of the PEG-precipitation method

BACKGROUND

Chronic elevated AST without other signs of liver disease, cardiac or skeletal abnormalities, is suggestive for macro-AST. Laboratory detection can be performed by gel filtration chromatography, ultrafiltration or precipitation with polyethylene glycol (PEG).

PATIENT AND METHODS

A healthy 27 year-old female was referred because of chronic elevated AST (116-704U/L) without other abnormalities. Macro-AST positivity was suspected since AST was no longer measurable in the supernatant of a serum sample (<3U/L) after PEG precipitation. Optimization of this method included analysis of proteins and lipids precipitated, testing the effect of different PEG concentrations and centrifugation times. 25% (m/v) PEG solution gave the most reliable results. No significant difference was seen between 10 and 30 min centrifugation time. A reference range was obtained by analysis of 31 normal patient samples (mean % PEG precipitation activity 35.1% with 95% confidence limits of 14.5-62.5%). Retrospective analysis of 1371 patient samples with elevated AST revealed one other positive patient sample.

CONCLUSION

Early recognition of macro-AST, proven by simple PEG precipitation, can avoid time-consuming and invasive investigations.