Reversibility of serum NH3 level in a case of sudden onset and rapidly progressive case of type 2 citrullinemia

Hyperammonemia: What Urea-lly Need to Know: Case Report of Severe Noncirrhotic Hyperammonemic Encephalopathy and Review of the Literature

Purpose. A 66-year-old man who presented with coma was found to have isolated severe hyperammonemia and diagnosed with a late-onset urea-cycle disorder. He was treated successfully and had full recovery. Methods. We report a novel case of noncirrhotic hyperammonemia and review the literature on this topic. Selected literature for review included English-language articles concerning hyperammonemia using the search terms “hyperammonemic encephalopathy”, “non-cirrhotic encephalopathy”, “hepatic encephalopathy”, “urea-cycle disorders”, “ornithine transcarbamylase (OTC) deficiency”, and “fulminant hepatic failure”. Results. A unique case of isolated hyperammonemia diagnosed as late-onset OTC deficiency is presented. Existing evidence about hyperammonemia is organized to address pathophysiology, clinical presentation, diagnosis, and treatment. The case report is discussed in context of the reviewed literature. Conclusion. Late-onset OTC deficiency presenting with severe hyperammonemic encephalopathy and extensive imaging correlate can be fully reversible if recognized promptly and treated aggressively.

Liver transplantation versus conservative treatment for adult-onset type II citrullinemia: our experience and a review of the literature

Adult-onset type II citrullinemia (CTLN2), an autosomal recessive disorder caused by a mutation in the SLC25A13 gene, is characterized by increased serum citrulline and ammonia levels. Patients with CTLN2 also display various neuropsychiatric symptoms. Many individuals with CTLN2 are fond of protein-rich and/or lipid-rich foods with an aversion to carbohydrate-rich foods. We herein report two cases of CTLN2 treated with living donor liver transplantation (LDLT) and provide a review of the pertinent literature. Case 1 was a 43-year-old man admitted to our hospital for repetitive episodes of consciousness disturbance. Case 2 was a 37-year-old man admitted to our hospital because of abnormal behavior associated with hyperammonemia. A definitive diagnosis of CTLN2 was accomplished by DNA analysis in both patients, who successfully underwent LDLT using liver segments from donor siblings with confirmed heterozygous gene expression. Case 2 also underwent conservative therapy with arginine and a high-fat, carbohydrate-restricted diet prior to LDLT. Postoperative recovery was uneventful and food was unrestricted in both patients. We also identified 77 cases of CTLN2 in the literature and reviewed them in terms of outcome of both liver transplantation and conservative therapy. The survival rate in patients treated by liver transplantation was 100%, whereas that in patients treated by conservative treatment showed improvement from 39.5% to 76.5% over the years. Liver transplantation is a practical treatment that fundamentally improves patient quality of life after transplantation. However, recent studies have suggested that arginine and sodium pyruvate administration combined with intensive nutritional support is also an effective therapy for CTLN2. Further development of conservative therapy may provide a safer, more affordable alternative to liver transplantation in the near future.

Noncirrhotic hyperammonaemic encephalopathy

Adult hyperammonaemia is associated with severe liver disease in 90% of cases. In the remainder, noncirrhotic causes should be considered. Measurements of serum ammonia level must be part of the basic work-up in all patients presenting with encephalopathy of unknown origin, even when liver function is normal. Clinician awareness of noncirrhotic hyperammonaemic encephalopathy can contribute to early diagnosis and the initiation of sometimes life-saving treatment. This review focuses on the physiology, aetiology and underlying mechanisms of noncirrhotic hyperammonaemic encephalopathy and discusses the available treatment modalities.

Reduced carbohydrate intake in citrin-deficient subjects

Citrin is the liver-type aspartate-glutamate carrier that resides within the inner mitochondrial membrane. Citrin deficiency (due to homozygous or compound heterozygous mutations in the gene SLC25A13) causes both adult-onset type II citrullinaemia (CTLN2) and neonatal intrahepatic cholestasis (NICCD). Clinically, CTLN2 is characterized by hyperammonaemia and citrullinaemia, whereas NICCD has a much more varied and transient presentation that can include multiple aminoacidaemias, hypoproteinaemia, galactosaemia, hypoglycaemia, and jaundice. Personal histories from CTLN2 patients have repeatedly described an aversion to carbohydrate-rich foods, and clinical observations of dietary and therapeutic outcomes have suggested that their unusual food preferences may be directly related to their pathophysiology. In the present study, we monitored the food intake of 18 Japanese citrin-deficient subjects whose ages ranged from 1 to 33 years, comparing them against published values for the general Japanese population. Our survey confirmed a marked decrease in carbohydrate intake, which accounts for a smaller proportion of carbohydrates contributing to the total energy intake (PFC ratio) as well as a shift towards a lower centile distribution for carbohydrate intake relative to age- and sex-matched controls. These results strongly support an avoidance of carbohydrate-rich foods by citrin-deficient patients that may lead to worsening of symptoms.

Hyperammonemia in the ICU

Patients experiencing acute elevations of ammonia present to the ICU with encephalopathy, which may progress quickly to cerebral herniation. Patient survival requires immediate treatment of intracerebral hypertension and the reduction of ammonia levels. When hyperammonemia is not thought to be the result of liver failure, treatment for an occult disorder of metabolism must begin prior to the confirmation of an etiology. This article reviews ammonia metabolism, the effects of ammonia on the brain, the causes of hyperammonemia, and the diagnosis of inborn errors of metabolism in adult patients.

Risk of worsened encephalopathy after intravenous glycerol therapy in patients with adult-onset type II citrullinemia (CTLN2)

OBJECTIVE

We report a risk of worsening of encephalopathy by glycerol infusion when this osmotic agent is used for the treatment of brain edema in patients with adult-onset type II citrullinemia (CTLN2) caused by citrin deficiency.

PATIENTS AND METHODS

We performed a retrospective investigation of 3 patients with CTLN2 treated for brain edema at our institute: a 31-year-old male patient and a 40-year-old female patient received treatment for encephalopathy-related brain edema with 10% glycerol infusion and 20% D-mannitol, and a 40-year-old male patient received only 20% D-mannitol infusion. In addition, we also performed a retrospective study in 11 CTLN2 patients reported previously (8 patients treated with 10% glycerol, 2 treated with 10% glycerol and 20% mannitol, and 1 treated with 20% mannitol).

RESULTS

The 12 patients treated with 10% glycerol, including 2 of our patients, died due to rapidly deteriorating encephalopathy and brain edema. On the other hand, the 2 patients who received only 20% D-mannitol, including one of our patients, recovered with the disappearance of brain edema.

CONCLUSION

In CTLN2 patients, glycerol infusion seems to be associated with exacerbation of encephalopathy itself and only mannitol should be used for the treatment of brain edema in patients with this disorder.

Adult-onset type II citrullinemia and idiopathic neonatal hepatitis caused by citrin deficiency: involvement of the aspartate glutamate carrier for urea synthesis and maintenance of the urea cycle

Citrin is a mitochondrial aspartate glutamate carrier primarily expressed in the liver, heart, and kidney. We found that adult-onset type II citrullinemia is caused by mutations in the SLC25A13 gene that encodes for citrin. In this report, we describe the frequency of SLC25A13 mutations, the roles of citrin as a member of the urea cycle and as a member of the malate-aspartate shuttle, the relationship between its functions and symptoms of citrin deficiency, and therapeutic issues.

Type II (adult onset) citrullinaemia: clinical pictures and the therapeutic effect of liver transplantation

OBJECTIVE

Adult onset type II citrullinemia is an inherited disorder of amino acid metabolism caused by a deficiency of liver specific argininosuccinate synthetase activity. Most of the patients with this disease were reported in Japan and therefore, this disease has not been well recognised outside this country. The detailed clinical pictures of the patients with type II citrullinaemia are reported and their outcomes after liver transplantation referred to.

METHODS

Ten patients with this disease were evaluated. Seven of them underwent liver transplants using a graft obtained from a healthy family member.

RESULTS

There were six men and four women; the age of onset of encephalopathy ranged from 17 to 51 years. The initial symptom in nine patients was sudden onset disturbance of consciousness, and one patient had long been regarded as having a chronic progressive psychotic illness. High concentrations of plasma citrulline and ammonia were commonly seen on admission. Although brain CT or MRI lacked any consistent findings, the EEG was abnormal in all patients, showing diffuse slow waves. Additionally, in five patients chronic pancreatitis preceded the onset of encephalopathy. After liver transplantation the metabolic abnormalities, including abnormal plasma concentrations of citrulline and ammonia, were immediately corrected and all neuropsychic symptoms soon disappeared, except for impaired cognitive function in one patient. Six out of these seven patients returned to their previous social lives, including work.

CONCLUSIONS

The clinical concept of adult onset type II citrullinaemia coincides well with the range of hepatic encephalopathy, and liver transplantation is a very promising therapeutic approach.