Citrullinemia

Melon Hyperlipemia acid urea cycle metabolic abnormalities are one of these diseases are caused because of the lack of enzymes. Urea cycle, melon acid (citrulline) are Carbamoyl phosphate and Ornithine (Ornithine) after a product. Under normal circumstances, melon acid succinate further by spermidine synthase (argininosuccinate synthetase) and aspartic acid (asparate) combine to produce succinate spermine (argininosucinate, AS). Each molecule of urea contains two nitrogen atoms (N), one from ammonia (NH3), and one from aspartic acid (asparate). argininosuccinate synthetase resulted in the lack of melon acid accumulation, known as the melon acid type hyperlipidemia.

Most nitrogen from protein and amino acid metabolism, and urea nitrogen cycle is the body to remove the main path. Mainly in the liver urea cycle performance, the response has mostly mitochondrial, have a part in the cytoplasm are inside, be able to put a toxic substance (ammonia), converted into a more non-toxic substances (urea), then by the urine Medium discharged. Mitochondria may affect the metabolism of urea generation, lead to high blood ammonia disease. Overall speaking, urea cycle by N-acetyl glutamic acid (N-acetylglutamate, NAG) control the speed of synthesis, the enzyme catalyst (NAG) open the ammonia into the urea cycle.

Argininosuccinate synthetase general will be transported to the brain, kidney, skin and fibrous tissue the role of mother cells, so melon acid can also be other than by metabolism in the liver. Melon acid in patients with hyperlipidemia a genetic defect will be manifested in these organizations. Urea cycle, melon aspartic acid and lysine combination, the second waste nitrogen molecules to enter the circle; when the urea cycle of damage, resulting in the ability of ammonia excretion decreased by 50%, have high blood ammonia in patients with disease situation .

Genetic model

Japan had cases in the adults find some kind of specific, previously undetected and treatment of hyperlipidemia melon acid, but also has patients after 48-year-old was found. Since some patients have developmental delay period, but most patients are only the incidence of symptoms. Melon acid so the incidence of hyperlipidemia in patients with age and ornithine amino-acyl transfer A deficiency (Orinithine transcarbamylase deficiency) are as unpredictable. Mortality and morbidity rates are high.

Melon acid hyperlipidemia for autosomal recessive genetic disease, both parents are carriers of the recessive (carrier: the Parent with a defective gene, but no clinical symptoms), the patient must at the same time with two a defect gene (from the Parent a) before the incidence. As long as both parents are carriers, 25% chance of giving birth to children, has 50% chance of a child for the carriers. The disease has no gender-neutral probability.

Melon acid Hyperlipemia ninth pathogenicity gene located on chromosome long arm (9q34). Have at least 20 point mutations have been discovered. Age at onset urea cycle and other metabolic disorders the same as the incidence of indeterminate age, the most common age of onset of the neonatal period. The neonatal period did not grow up the children with treatment, may have the consequences of mental retardation.

Symptoms

Symptoms of high blood ammonia, along with lack of appetite, vomiting, fatigue, irritability, cramps; cerebral edema and coma if not treated in time may cause death. Incidence of the neonatal period is usually, but symptoms may be a few days or weeks before unnoticed. The severity of clinical symptoms and rely on their individual circumstances vary. In general there may be high ammonia conditions, the growth of the poor. If cerebral edema may result in papilledema (papilledema), intracranial pressure will also increase. Lung area, there may be shortness of breath or too strong case may be will be late apnea or failure. Moderate hepatomegaly may also happen phenomenon. Neural connection, there may be poor coordination disorder power sports (dysdiadochokinesia), the tension is too low or too strong, ataxia, tremor, cramps, drowsiness. Complications mainly neuropathy, including mental retardation, acute high blood ammonia coma, or even death.

Diagnosis

The symptoms of patients, first and foremost is the measurement of blood ammonia (NH3) concentrations, useful for diagnosis on biochemical values. Another is a measure of blood amino acid concentration, incidence of the patients, their blood will be obvious melon acid increased to 1000-5000  M (normal 10-20  M). Urinary concentrations of amino acids, organic acid concentration and urinary orotic acid (orotic acid) can also be used as the reference value. Patients with urine orotic acid concentrations rise.
Measurement of skin cells of fibrous tissue Argininosuccinate synthetase, could provide specific biochemical diagnosis.

Prenatal diagnosis

Do amniocentesis (amniocytes) or chorionic villi to do molecular diagnostics.

Treatment

The goal of treatment is to correct the biochemical imbalance and to ensure that nutritional requirements. Under the situation of high ammonia immediately restricted diet of protein, strengthen the non-protein energy sources, to avoid compensatory disorders. Serious, it is possible to quickly remove ammonia hemodialysis.

Low-protein diet
According to patient's age and disease severity of the decision of protein intake, each patient's needs are quite different. Six months ago, because it is fast-growing period, patients may need more protein or 1.5g/kg/day; preschool period, protein intake is usually reduced to 1.2 ~ 1.5g/kg/day; school-age children may be to fell 1 g / kg / day. After puberty, the amount of protein may be less than 0.5g/kg/day.

Drug
Drugs to provide an alternative way to rule out the possibility of waste nitrogen.
1.Sodium benzoate (Ucephan): with glycine (glycine) combine to form hippuric acid (hippurate), and then discharged by the urine. Every one mole of benzoate to remove one mole of nitrogen. Usually give the IV dose is 250 mg / kg / day; oral dose of 375mg/kg/day, minutes 3-4 times taking it and with a low-protein diet. Side effects of nausea, vomiting, tinnitus, visual impairment.
2.Sodium phenylbutyrate (Buphenyl): in the liver to be oxidized to phenylacetate, and then combined with glutamine, the final product phenylacetylglutamine discharged through the urine. 1 mole per 2 mole of phenylbutyrate to remove nitrogen. Given dose is 0.5 mg / kg / day.
3. Arginine (Arginine): by the enzyme arginase (arginase) after role, each 1mole arginine 1mole broken down into urea and ornithine 1mole of (ornithine). High blood ammonia circumstances, given doses of 600 mg / kg / day. Give children with a stable oral dose of 400-700 mg / kg / day.

Prognosis of patients and age and the condition relating to the time of diagnosis. At the neonatal period there are symptoms of the patients, their prognosis is poor, the majority of patients will have some obvious complications. Required long-term cooperation with physicians and nutritionists with the continued out-patient follow-up biochemical tests conducted on a regular basis, recording height and weight development in order to grasp the situation of patients.