These sweeteners are not common in formulas used today. Symptoms such as vomiting, nausea, restlessness, pallor, sweating, trembling and lethargy can also first present in infants when they are introduced to fruits and vegetables. These can progress to apathy, coma and convulsions if the source is not recognized early.When patients are diagnosed with HFI, a dietary history will often reveal an aversion to fruit and other foods that contain large amounts of fructose. Most adult patients do not have any dental caries. Fructose metabolism
After ingestion, fructose is converted to fructose-1-phosphate in the liver by fructokinase. Deficiencies of fructokinase cause essential fructosuria, a clinically benign condition characterized by the excretion of unmetabolized fructose in the urine. Fructose-1-phosphate is metabolized by aldolase B into dihydroxyacetone phosphate and glyceraldehyde. HFI is caused by a deficiency of aldolase B.A deficiency of aldolase B results in an accumulation of fructose-1-phosphate, and trapping of phosphate (fructokinase requires adenosine triphosphate (ATP)). The downstream effects of this enzyme block are the inhibition of glucose production and reduced regeneration of ATP. Diagnosis
Because of the ease of therapy (dietary exclusion of fructose), HFI can be effectively managed if properly diagnosed. In HFI, the diagnosis of homozygotes is difficult, requiring a genomic DNA screening with allele-specific probes or an enzyme assay from a liver biopsy.
In the case of mediastinal lymphadenopathy, the enlarged lymph node causes compression of the lymphatic channels and thoracic duct. This impedes the centripetal drainage of the flow of lymph from the edges of the lung parenchyma and pleural surfaces. This causes the chyle to ooze extensively into the pleural cavity, leading to a chylothorax. In the case of yellow nail syndrome, or lymphedema, chylothorax is caused by hypoplasia or dilation of the lymph vessels. In rare cases, like in hepatic chylothorax, chylous ascites crosses the diaphragm into the pleural cavity. In idiopathic cases like genetic disorders, the mechanism is not known. Up to three liters of chyle can easily drain into the pleural space daily. Diagnosis
Chest X-rays can detect a chylothorax. It appears as a dense, homogeneous area that obscures the costophrenic and cardiophrenic angles. Ultrasounds can also detect a chylothorax, which appears as an echoic region that is isodense with no septation or loculation. However, neither a normal chest x-ray nor an ultrasound can differentiate a chylothorax from any other type of pleural effusion. The cisterna chyli can be found in a thoracic MRI, making it possible to confirm chylothorax. However, MRI is not the ideal method to scan the thorax, and so it is rarely used. Another diagnostic technique is conventional lymphangiography. It is rarely used since there are equally sensitive yet less invasive techniques available to identify a chylothorax. Lymphangiography procedures use the contrast dye agent lipiodol, which is injected into the lymphatic vessels.