Coma, hyperammonemia, metabolic acidosis, and mutation: lessons learned in the acute management of late onset urea cycle disorders

Inherited metabolic disorders in the neonatal intensive care unit: Red flags to look out for

BACKGROUND

We aimed to assess symptoms, laboratory findings, and radiological abnormalities in patients diagnosed with inherited metabolic disorders (IMDs) in the neonatal intensive care unit.

METHODS

A total of 6,150 newborns treated in a third-level neonatal intensive care unit between 2012 and 2020 in Turkey were screened, of which 195 consulted with a suspicion of metabolic disease based on their clinical, laboratory, or radiological findings were included in the present study.

RESULTS

The prevalence of IMDs in the patients was 1:94.6. Those consulted in the department of pediatric metabolism were divided into two groups, with the 65 diagnosed with IMDs assigned as Group I, and the 130 patients who were not diagnosed with IMDs as Group II. The most common IMDs were organic acidemias (29.23%) and urea cycle disorders (UCDs) (26.15%). The rates of consanguinity marriage (75.3% vs 37.6%, P < 0.001), siblings diagnosed with an IMD (27.6% vs 3.8%, P < 0.001), and sibling death (56.9% vs 14.6%, P < 0.001) were higher in Group I than in Group II. Hyperammonemia (61.5% vs 18.4%, P < 0.001) was the most common laboratory finding in Group I, and anemia (Group I 60.0% vs 43.0% P = 0.033), metabolic acidosis (53.8% vs 36.9%, P = 0.028) and respiratory alkalosis (16.9% vs 1.5%, P < 0.001) were all higher in Group I.

CONCLUSIONS

This retrospective study found that the results of clinical findings and basic laboratory tests could be strong indicators of IMDs, although extensive newborn screening tests and advanced biochemical and genetic tests should be carried out for the diagnosis of IMDs in newborns.

Laboratory diagnostic approaches in metabolic disorders

The diagnosis of inborn errors of metabolism (IEM) takes many forms. Due to the implementation and advances in newborn screening (NBS), the diagnosis of many IEM has become relatively easy utilizing laboratory biomarkers. For the majority of IEM, early diagnosis prevents the onset of severe clinical symptoms, thus reducing morbidity and mortality. However, due to molecular, biochemical, and clinical variability of IEM, not all disorders included in NBS programs will be detected and diagnosed by screening alone. This article provides a general overview and simplified guidelines for the diagnosis of IEM in patients with and without an acute metabolic decompensation, with early or late onset of clinical symptoms. The proper use of routine laboratory results in the initial patient assessment is also discussed, which can help guide efficient ordering of specialized laboratory tests to confirm a potential diagnosis and initiate treatment as soon as possible.

Ornithine transcarbamylase deficiency that developed at the age of 19 years with acute brain edema

Case

A 19-year-old man had nausea, diarrhea, and general malaise the day before requesting emergency transport to his former primary physician. The patient became restless and had tonic seizures after admission. The patient was transferred to our hospital as there had been no improvement in his level of consciousness. On arrival, cranial computed tomography showed generalized swelling, and blood ammonia concentration was ≥500 μg/dL. After admission, seizures recurred continually despite careful monitoring and increased doses of sedatives and antiseizure drugs. Dilated pupils and a flat electroencephalogram were evident on day 4 of admission, and the patient died on day 11. Ornithine transcarbamylase deficiency was diagnosed at postmortem based on fractionation of blood and urine amino acids and orotic acid.

Outcome

Urea cycle disorders need to be treated urgently to prevent irreversible neurological damage when accompanied by hyperammonemia.

Conclusion

In cases of hyperammonemia, early dialysis should be considered to reduce the ammonia level.

Guidelines for acute management of hyperammonemia in the Middle East region

Background

Hyperammonemia is a life-threatening event that can occur at any age. If treated, the early symptoms in all age groups could be reversible. If untreated, hyperammonemia could be toxic and cause irreversible brain damage to the developing brain.

Objective

There are major challenges that worsen the outcome of hyperammonemic individuals in the Middle East. These include: lack of awareness among emergency department physicians about proper management of hyperammonemia, strained communication between physicians at primary, secondary, and tertiary hospitals, and shortage of the medications used in the acute management of hyperammonemia. Therefore, the urge to develop regional guidelines is extremely obvious.

Method

We searched PubMed and Embase databases to include published materials from 2011 to 2014 that were not covered by the European guidelines, which was published in 2012. We followed the process of a Delphi conference and involved one preliminary meeting and two follow-up meetings with email exchanges between the Middle East Hyperammonemia and Urea Cycle Disorders Scientific Group regarding each draft of the manuscript.

Results and discussion

We have developed consensus guidelines based on the highest available level of evidence. The aim of these guidelines is to homogenize and harmonize the treatment protocols used for patients with acute hyperammonemia, and to provide a resource to not only metabolic physicians, but also physicians who may come in contact with individuals with acute hyperammonemia.

Conclusion

These suggested guidelines aim to ease the challenges faced by physicians dealing with acute hyperammonemia in the region. In addition, guidelines have demonstrated useful collaboration between experts in the region, and provides information that will hopefully improve the outcomes of patients with acute hyperammonemia.