What is Idiopathic Neonatal Hepatitis?

Idiopathic neonatal hepatitis (INH) is a general term for inflammation of the liver that occurs shortly after birth in newborns (less than 3 months of age) for which a specific cause cannot be identified.  Neonatal hepatitis can have one of a number of causes including metabolic, infectious, and genetic causes.  Metabolic diseases include αa1-antitrypsin deficiency, cystic fibrosis, neonatal iron storage disease, respiratory chain defects, and fatty acid oxidation defects. Infectious causes include congenital syphilis, echovirus, and some herpes viruses.  The classic hepatitis viruses (A, B, and C) are less common causes. There are also a number of less common genetic defects, such as Alagille syndrome and progressive familial intrahepatic cholestasis.  In Idiopathic Neonatal Hepatitis, however, the cause of inflammation remains unknown.

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What are the symptoms?

The symptoms of idiopathic neonatal hepatitis can vary greatly from one individual to another.  Infants with INH may have jaundice as their only symptom; usually in the first two weeks of life developing up to the third month of life.  There may also be the presence of dark urine, pale stools and enlargement of the liver, Other symptoms may also include poor growth, irritability, and severe itching.

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How is it diagnosed?

The greatest challenge in diagnosing idiopathic neonatal hepatitis is in differentiating it from other neonatal liver diseases with known causes.  INH is diagnosed when tests for  metabolic, infectious, and genetic causes are negative.  This is done through blood tests, hepatobiliary scans, metabolic or genetic testing, and a liver biopsy.  On biopsy, the hepatocytes are enlarged, often filled with bile, and sometimes dying. There may be early scarring in some instances. Electron micrscopic examination is sometimes useful in detecting otherwise subtle changes and directing further testing.

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How is it treated?

Since there is no known cause in idiopathic neonatal hepatitis, treatment is focused on symptom management and good nutritional support. This includes medications to stimulate bile flow, predigested formulas, and extra vitamins A, D, E, and K, which are important because the lack of bile in the intestine impairs absorption of those vitamins.

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What is the outlook for infants diagnosed with INH?

Approximately 80% of infants diagnosed with idiopathic neonatal hepatitis recover fully from the condition. Over the years, as more specific causes of neonatal jaundice are diagnosed, the number of cholestatic infants without a specific diagnosis has decreased. It is expected that this number will continue to decrease as more specific causes are described.

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