Chronic Genetic Liver Diseases

Wilson’s disease

Pathogenesis

Wilson’s disease is a treatable, genetic disorder. The metabolic defect leads to progressive accumulation of copper in the liver, brain (particularly in the basal ganglia), cornea, and kidneys, causing severe functional impairment leading to irreversible damage. If not treated, this disease is invariably fatal, but with early diagnosis and treatment, the clinical manifestations can be prevented and reversed.

Wilson’s disease is an autosomal recessive disorder. The abnormal gene is distributed worldwide with a prevalence of heterozygotes of one in 200 and homozygotes of one in 30,000. The genetic defect is on chromosome 13 near the red-cell esterase locus. In 95% of patients, there is also an absence or deficiency of serum ceruloplasmin, the main copper-transporting protein in blood. This deficiency is caused by a decrease in transcription of the ceruloplasmin gene located on chromosome 3.

Copper metabolism

Copper concentration in the liver. The liver of a human newborn contains six to eight times the copper concentration of an adult liver. Within the first 6 months of life, this diminishes to a concentration of 30 mg/g of dry tissue. Thereafter, throughout life, the liver concentration of copper is maintained at this steady state by careful regulation of intestinal absorption and transport and of the liver stores through the synthesis of plasma and tissue copper proteins and excretion of copper from the body in the bile.

Absorption and excretion

Approximately 50% of the average dietary intake of 2 to 5 mg of copper is absorbed from the proximal small intestine and loosely binds to albumin. It is promptly cleared by the liver, where it is incorporated into specific copper proteins such as cytochrome oxidase and ceruloplasmin or is taken up by lysosomes before being excreted in bile. There are two main routes by which copper is mobilized from the liver.

Synthesis of copper-containing ceruloplasmin and its release into the circulation.

Biliary excretion amounting to 1.5 mg of copper per day. This is the principal route of elimination of copper from the body.

The copper excess seen in Wilson’s disease has been shown to be the result of decreased biliary excretion and not an increase in the absorption of copper. The defect is caused by mutations in the ATP7B gene in the hepatocytes, resulting in accumulation of copper by the hepatocytes.

Copper toxicity

• Acute toxicity. Ingestion of gram quantities of copper causes serious gastrointestinal and systemic injuries and occasionally hepatic necrosis. Generally, however, the vomiting and diarrhea that follow the ingestion of copper salts protect the patient from serious toxic effects.
• Chronic toxicity. Hepatic copper overload may occur in disorders other than Wilson’s disease. These include primary biliary cirrhosis, extrahepatic biliary artesian, Indian childhood cirrhosis, and other chronic cholestatic disorders. The excess hepatic copper may aggravate the underlying pathologic process by direct damage to the organelles or through promotion of fibrosis.

Diagnosis

Clinical presentation

Wilson’s disease has many modes of presentation. It may simulate several different neurologic and psychiatric disorders. It may present as asymptomatic transaminasemia, chronic active hepatitis, fulminant hepatitis, cirrhosis of the liver, acquired hemolytic anemia, renal disease, or eye abnormalities such as sunflower cataracts and Kayser-Fleischer (K-F) rings.

Liver disease is the most common presentation of Wilson’s disease in childhood. About 40% of all patients with Wilson’s disease come to medical attention with evidence of liver disease. Because an increase of 30 to 50 times the normal hepatic concentration of copper can occur without any clinical manifestations, symptoms of liver disease do not appear before 6 years of age. However, one half of the patients have symptoms by 15 years of age. Thus, overt Wilson’s disease is encountered predominantly in older children, adolescents, young adults, and rarely in older adults.

Forms

The hepatic disease may take several different forms.

Commonly it begins insidiously and runs a chronic course characterized by weakness, malaise, anorexia, mild jaundice, splenomegaly, and abnormal liver chemistry tests. The disease may mimic acute viral hepatitis, mononucleosis, or chronic active hepatitis.

Fulminant hepatitis may occur suddenly, characterized by progressive jaundice, ascites, and hepatic failure. The outcome is usually fatal, particularly when the disorder is accompanied by hemolytic anemia.

Some patients present with the typical picture of postnecrotic cirrhosis with spider angiomata, splenomegaly, portal hypertension, ascites, bleeding esophageal varices, or thrombocytopenia mimicking idiopathic thrombocytopenic purpura. The liver enzymes may be normal. The diagnosis of Wilson’s disease should always be considered in patients younger than 30 years with negative serology for viral hepatitis; with a history of chronic active hepatitis; or with juvenile, cryptogenic, or familial cirrhosis. Although fewer than 5% of such patients have Wilson’s disease, it is one of the few forms of liver disease for which specific and effective therapy is available.

Histology

There is no one specific histologic profile to identify Wilson’s disease in liver biopsy specimens. In the early stages of copper accumulation, when copper is diffusely distributed in the cytoplasm, it is undetectable by rhodanine or rubeanic acid stains. At this stage, lipid droplets are seen in the hepatocytes with ballooned, vacuolated nuclei containing glycogen. This initial steatosis progresses to fibrosis and ultimately to cirrhosis. With time and progression of the liver disease, the hepatocyte lysosomes seem to sequester the excess copper, which is detectable throughout some nodules by routine histochemical staining.

Because of the variable stainability and the irregular distribution of copper among adjacent nodules, absence of a positive rhodanine or rubeanic acid stain on a histologic slide does not exclude the diagnosis of Wilson’s disease. The parenchyma usually is infiltrated with mononuclear cells. There may be cholestasis, focal necrosis, and Mallory’s hyalin. In other cases, the histology may resemble that of acute or chronic active hepatitis.

Once macronodular cirrhosis develops, the microscopic findings are nonspecific. Hepatocytes may contain some cytoplasmic lipid, vacuolated glycogen-containing nuclei, and cytoplasmic inclusions containing copper-rich lipofuscin granules.

Neurologic disease is the most common presentation of Wilson’s disease. The usual age of onset is 12 to 32 years. The most common symptoms are as follows:

Incoordination particularly involving fine movements such as handwriting, typing, and piano playing.

Tremor is usually at rest but intensifies with voluntary movement and emotion. It ranges from a fine tremor of one hand to generalized tremor of the arms, tongue, and head. It may be slow, coarse, or choreoathetoid. Dystonia, ataxic gait, spasticity, and rigidity are late neurologic manifestations.

Dysarthria begins with difficulty in enunciating words and progresses to slurring of speech, microphonia, and aphasia.

Excessive salivation occurs early in the course of the disease.

Dysphagia is progressive and oropharyngeal; patients have difficulty initiating swallowing, leading to regurgitation and aspiration.

K-F rings are corneal copper deposits laid in the Descemet’s membrane in layers appearing as granular brown pigment around the periphery of the iris. They may be absent in early stages but are present in all patients in the neurologic stage of Wilson’s disease. Most K-F rings can be visualized by the naked eye, but some require slit-lamp examination.

Psychiatric disease

Almost all of the patients demonstrate some form of psychiatric disturbance, which may appear as teenage adjustment behavior, anxiety, hysteria, or a manic-depressive or schizoaffective disorder. Psychotropic drugs may accentuate the neurologic manifestations of Wilson’s disease and increase the patient’s problems.

Hematologic disease

In a few patients, Wilson’s disease presents as a Coombs-negative hemolytic anemia with transient jaundice. It may be intermittent and benign, or it may occur with fulminant hepatitis. The hemolysis occurs during phases of hepatocellular necrosis with sudden release of copper from necrotic hepatocytes into the circulation. This effect is indicated by a marked rise in the concentration of nonceruloplasmin copper in the blood and in the amount of copper excreted through the urine.

With portal hypertension and splenomegaly, hypersplenism may result in thrombocytopenia and pancytopenia. Progressive liver disease also gives rise to clotting factor deficiencies and bleeding.

Kidney disease

Renal abnormalities result from accumulation of copper within the renal parenchyma. These abnormalities range from renal insufficiency with decreased glomerular filtration rate to proximal tubular defects resembling Fanconi’s syndrome, renal tubular acidosis, proteinuria, and microscopic hematuria.

Bone and joint disease. Especially in patients with Fanconi’s syndrome, renal calcium loss, osteomalacia, or renal tubular acidosis, increased bone resorption occurs and leads to bone loss. Osteoarthritis and bone fractures are common and are exacerbated by patients’ neurologic and gait disturbances.

Diagnostic studies

Serum ceruloplasmin

Ninety-five percent of patients with Wilson’s disease have a serum ceruloplasmin concentration less than 20 mg/dL. Because approximately 20% of heterozygotes also have diminished levels, deficiency of ceruloplasmin is not sufficient for the diagnosis of Wilson’s disease. Patients with fulminant hepatitis and 15% of patients with Wilson’s disease presenting with only a hepatic disorder may have a ceruloplasmin concentration of 20 to 30 mg/dL due to a slight increase of this acute-phase reactant protein with inflammation. Hypoceruloplasminemia also may be found in patients with nephrotic syndrome, protein-losing enteropathy, or malabsorption; these conditions can be distinguished easily from Wilson’s disease.

Serum copper

Because ceruloplasmin is the main copper-transporting protein in the blood, total serum copper levels are often decreased in patients with Wilson’s disease, but free copper is elevated and is therefore responsible for excess copper deposition in various tissues. The determination of the serum free copper concentration represents the most reliable finding for the initial diagnosis of Wilson’s disease. This value is calculated as the difference between total serum copper concentration and the amount of copper bound to ceruloplasmin (0.047 mmol of copper per milligram of ceruloplasmin).

Urinary copper excretion

Serum free copper is readily filtered by the kidneys and accounts for the increased urinary copper excretion seen in Wilson’s disease. Most patients have urinary copper excretion levels greater than 1.6 mmol per day. However, urinary copper levels often are elevated also in patients with cirrhosis, chronic active hepatitis, or cholestasis. This measurement does not distinguish these entities from Wilson’s disease, therefore, despite the administration of D-penicillamine, an agent that increases urinary copper excretion.

Liver biopsy should be obtained for histologic studies and quantitative hepatic copper concentration. Hepatic copper concentration in excess of 250 Вµg/g. Edition of dry tissue is compatible with the diagnosis of Wilson’s disease. To obtain a reliable result, it is essential that contamination of the specimen with traces of copper be avoided (a disposable biopsy needle minimizes this hazard) and that an adequate sample (ideally 1 cm in length) be submitted for analysis.

A transjugular biopsy is inadequate for quantitative purposes. Other disorders such as primary and secondary biliary cirrhosis and long-standing bile duct obstruction can also lead to a very elevated hepatic copper concentration by interfering with hepatic excretion of copper into bile. These patients, however, have elevated ceruloplasmin levels.

In the rare patient with a normal serum ceruloplasmin concentration in whom a liver biopsy is contraindicated because of clotting abnormalities, a radiocopper loading test can be performed using ⁶⁴Cu, with a half-life of 12.8 hours, given to patients by mouth (p.o.) (2 mg) or intravenous (intravenous) (500 mg); the serum concentration of radioactive copper is plotted with time in hours.

In individuals who do not have Wilson’s disease, radioactive copper appears and disappears from the serum within 4 to 6 hours. A secondary rise of radioactivity appears in the serum after the isotope is incorporated by the liver into freshly synthesized ceruloplasmin. In patients with Wilson’s disease, this secondary rise in radioactivity is absent, since the rate of hepatic incorporation of radiocopper into ceruloplasmin is diminished.

K-F rings are present in all patients with Wilson’s disease who have neurologic manifestations, but they may be absent in patients presenting only with hepatic disease. If they are not visible, they should be sought with slit-lamp examination.

In Wilson’s disease presenting as fulminant hepatitis, the combination of a disproportionately low serum alkaline phosphatase level and a comparatively modest aminotransferasemia with jaundice and clinical and histologic evidence of hepatic necrosis suggests Wilson’s disease. The ratio of the serum alkaline phosphatase to the total serum bilirubin also may be used.

All siblings of known patients should be screened for the possibility of Wilson’s disease by physical examination, slit-lamp examination of the corneas, and determinations of serum ceruloplasmin and aminotransferase concentrations.

Treatment

Untreated Wilson’s disease causes progressive damage of the liver, brain, and kidneys. Until the late 1940s, patients usually died before reaching 30 years of age. The prognosis improved substantially after the introduction of the copper-chelating agent _D-penicillamine in the 1950s. It is important to establish a firm diagnosis of Wilson’s disease, because the patient will be on lifelong therapy.

Diet

The dietary intake of copper should be less than 1.0 mg per day. Foods rich in copper such as organ meats, shellfish, dried beans, peas, whole wheat, and chocolate should be avoided.

D-Penicillamine was the first oral drug used for the treatment of any stage of Wilson’s disease. Penicillamine chelates heavy metals, especially copper, and facilitates their urinary excretion, thus shifting the equilibrium from tissues to plasma. It is also antiinflammatory and may interfere with collagen synthesis and fibrosis. Pyridoxine, 25 mg daily, is given to compensate for the weak antipyridoxine effects of penicillamine.

The usual daily dose is 0.75 to 2.0 g, p.o. The effectiveness of therapy can be monitored using the calculated free serum copper concentration, which should be less than 1.6 mmol/L. The earlier the therapy is instituted, the better the results. The histologic abnormalities and many of the symptoms are reversed; however, already established cirrhosis, portal hypertension, and some neurologic abnormalities such as dystonia, rigidity, dysarthria, and dementia may not be reversible.

Up to 20% of patients have sensitivity reactions within weeks of the institution of penicillamine therapy. These reactions include fever, rash, lymphadenopathy, polyneuropathy, leukopenia, and thrombocytopenia. Dose reduction or short-term interruption of penicillamine therapy followed by restarting treatment at slowly increasing doses is usually successful in overcoming these side effects. For the 5% to 10% of patients who have serious penicillamine toxicity (lupus, nephrotic syndrome, pemphigus, elastosis of skin, myasthenia gravis, thrombocytopenia, or severe arthralgias), another chelating agent, trientine dihydrochloride, may be used.

Trientine dihydrochloride is another chelating cupruretic agent used in the treatment of Wilson’s disease. It has less of a cupruetic effect than penicillamine, but its clinical effectiveness is comparable. Typical dosage for initial therapy in adults is 750 to 1500 mg per day in divided doses, and 750 to 1000 mg per day for typical maintenance therapy. Trientine dihydrochloridehas a better safety profile than penicillamine. No hypersensitivity reactions have been reported. Reversible sideroblastic anemia and bone marrow toxicity has been observed in patients who were over-treated with resultant copper deficiency. Due to its better safety profile, trientine dihydrochloride is now the drug of choice in the treatment of Wilson’s disease. Both _D-penicillamine and trientine dihydrochloride should be continued without interruption during pregnancy. Noncompliance with or interruption of the penicillamine or trientine dihydrochloride regimen is often followed by recurrence of symptoms or fulminant hepatitis.

Oral zinc

Orally administered zinc sulfate (200-300 mg three times daily [t.i.d.]) has been found to be effective in the treatment of Wilson’s disease, especially in patients who cannot tolerate cupruetic treatment. Orally administered zinc induces the synthesis of intestinal metallothionein, thus increasing the capacity for copper binding by the epithelial cells and trapping the metal in the intestinal mucosa, thereby preventing its systemic absorption. In addition, zinc may exert a protective effect by inducing metallothionein in the hepatocytes, thus decreasing the toxic effects of copper. In some patients, large doses of zinc are associated with headaches, abdominal cramps, gastric irritation, and loss of appetite. Zinc also interferes with absorption of iron, alters immune responses, and affects the serum lipoprotein profile.

Zinc is not recommended as the sole agent for initial therapy of symptomatic patients, but it is recommended as maintenance therapy at 150 mg per day in three divided doses to keep patients at negative copper balance. Zinc acetate is better tolerated than zinc chloride or sulfate.

Tetrathiomolybdate, an agent that appears to block the absorption of copper by holding the metal in a tight, metabolically inert bond, has been used in a few patients intolerant to penicillamine. The therapeutic role of this agent is to be determined.

Monitoring

Periodic physical examinations, slit-lamp examinations of the cornea for documentation of the disappearance of K-F rings, and measurements of 24-hour urinary copper excretion and serum free copper should be performed to assess the effectiveness of therapy.

Significant clinical improvement may occur only after 6 to 12 months of uninterrupted treatment.

Liver transplantation is a lifesaving procedure for patients with fulminant hepatitis or irreversible hepatic insufficiency due to Wilson’s disease. The metabolic abnormality is reversed and the disease is cured. One-year survival follow liver transplantation is now approximately 80%. Liver cell transplantation is currently under study as an alternative to liver transplantation.

Hemochromatosis

О±₁-antitrypsin deficiency

О±₁-antitrypsin is an acute-phase reacting О±-1 globulin found in serum, various body fluids, and tissues. It is a potent protease inhibitor synthesized by hepatocytes, monocytes, and bronchoalveolar macrophages for protection against tissue injury resulting from proteases such as trypsin, chymotrypsin, elastase, and collagenase as well as from proteases released from polymorphonuclear leukocytes and macrophages. Antitrypsin is responsible for 90% of the serum protease-inhibiting capacity and approximately 90% of the alpha-1 band on serum protein electrophoresis.

Antitrypsin is a glycoprotein consisting of a single polypeptide chain with four carbohydrate side chains. Due to genetic mutations, at least 60 variants of antitrypsin have been identified by their mobility on acid starch gel electrophoresis followed by crossed immunoelectrophoresis on agarose gel. Isoelectric focusing in polyacrylamide (PIEF) has replaced the starch gel techniques and offers increased resolution of protease inhibitor variants. These variant proteins (phenotypes) have been designated by different letters of the alphabet. The faster moving proteins have been assigned earlier letters of the alphabet: PIM is the most common protein with medium mobility, protease inhibitor S is slow, and protease inhibitor Z is the slowest.

The inheritance of antitrypsin is autosomal codominant. Each allele acts independently of the other and contributes its own active protein. The protease inhibitor locus is on chromosome 14. Phenotypes are usually expressed as two alleles. Common protease inhibitor variants associated with decreased plasma concentration of antitrypsin are protease inhibitor S at 60% and the classic deficiency phenotype protease inhibitor Z at 10% to 15% of normal levels. The rare alleles protease inhibitor I, protease inhibitor P, protease inhibitor M malton, and protease inhibitor M Duarte also have low plasma levels. Protease inhibitor null (protease inhibitor Ø or protease inhibitor-) phenotypes result in no detectable circulating antitrypsin. Protease inhibitor S is relatively common in Spain, whereas protease inhibitor Z is most common in Scandinavia.

The protease inhibitor MM phenotype is associated with an average serum level of 220 mg of antitrypsin/dL. Serum levels of antitrypsin may be increased by acute and chronic inflammation as a response to tissue injury, estrogen or oral contraceptive ingestion, pregnancy, carcinoma, and typhoid inoculation in normal individuals. In severely deficient individuals, the level rises only slightly with such stimuli.

When the livers of severely deficient subjects are examined histologically, accumulation of an amorphous material within most hepatocytes has been demonstrated. This material, like glycogen, takes the periodic acid-Schiff (periodic acid – Schiff) stain but, unlike glycogen, is resistant to digestion with diastase. This periodic acid – Schiff-positive material is a variant of antitrypsin that has been excreted out of the hepatocytes.

The greatest accumulation of this material is in the smooth endoplasmic reticulum. The basic difference in the structure of this protein (protease inhibitor Z) from that of the normal (protease inhibitor M) is the replacement of a glutamic acid by a lysine. This limits its transport out of smooth endoplasmic reticulum to the Golgi and thus its excretion from the hepatocytes, resulting in low serum levels of antitrypsin. Other, less severe types of antitrypsin deficiency have other amino acid substitutions.

Protease inhibitor M Duarte and M malton have nearly normal electrophoretic mobilities but are associated with low plasma levels, intracellular aggregates, and lung and liver disease. Protease inhibitor S has decreased stability and does not accumulate in the liver cells. The non-protease inhibitor M alleles are rare in African Americans. Protease inhibitor Z has its greatest frequency in northern Europe. In the United States, approximately 1 in 676 whites has severe antitrypsin deficiency.

It is clear that subjects of phenotype protease inhibitor ZZ and probably protease inhibitor SZ but not protease inhibitor MZ are much more susceptible to the development of emphysema or chronic bronchitis or both than the general population. This tendency is potentiated by smoking. The emphysema is usually of the panlobular type and affects the lower lobes first.

Where as emphysema is inversely related to plasma antitrypsin levels, liver disease correlates with intracellular accumulation of antitrypsin. Liver injury occurs in antitrypsin phenotypes associated with intracellular protein accumulation (protease inhibitor Z, protease inhibitor M malton, protease inhibitor M Duarte). In contrast, no liver disease is seen in deficiency phenotypes due to intracellular protein degradation (protease inhibitor S, protease inhibitor null). The pathogenesis of the liver injury is not clear.

Liver disease

The first genetic association of antitrypsin deficiency with liver disease and cirrhosis was made in children. Subsequently, its association with cirrhosis in adults has been confirmed. There is also an increased incidence of hepatic cancer in patients with cirrhosis.

In clinical studies involving protease inhibitor ZZ infants, it has been found that 12% present with cholestasis and another 7% present with other evidence of liver disease during early infancy. By 6 months of age, these infants appear to recover clinically from their liver disease but continue to have elevated liver enzymes. At 3 months of age, 47% of «normal» protease inhibitor ZZ infants have elevated liver enzymes. Only 34% of protease inhibitor ZZ infants have no clinical or laboratory evidence of liver injury. At 4 years of age, approximately one half of the protease inhibitor ZZ children continue to have elevated serum hepatic enzyme concentrations.

Roughly 75% of children with antitrypsin deficiency and clinically apparent liver disease present with jaundice and cholestasis during infancy. The remainder present with evidence of portal hypertension in later childhood. Only 25% of the cholestatic infants recover without evidence of chronic liver disease.

The severe degree of cholestasis in some infants with antitrypsin deficiency may simulate extrahepatic biliary obstruction with respect to both clinical evaluation and liver pathology. Surgical exploration in these instances has revealed «physiologic hypoplasia» of the extrahepatic biliary tract, secondary to decreased bile flow. Atresia of the ducts has not been demonstrated.

Approximately 25% of the children with antitrypsin deficiency who present with cholestasis persist in having grossly abnormal liver function tests. These patients develop cirrhosis and portal hypertension with ascites and esophageal varices, and die from hepatic complications in the first 10 years of life. Another 25% have evidence of persistently abnormal liver function tests but are slower in developing clinical signs of cirrhosis, and die of complications of their liver disease between 10 and 20 years of age. Another 25% have minimal liver dysfunction, minimal organomegaly, and less severe liver fibrosis and live to adulthood. The remaining 25% appear to recover from their initial insult and return to normal liver function with minimal evidence of residual liver fibrosis.

In adults, as in children, men are twice as likely to have liver disease as women. In studies done with patients with protease inhibitor ZZ phenotype from Sweden or of Northern European ancestry, the relative risk for cirrhosis was noted to be 37% to 47%, and of hepatoma, 15% to 29%. In studies done in heterozygotes of protease inhibitor MZ or protease inhibitor SZ phenotypes, the relative risk for cirrhosis was noted to be 1.8 and for hepatoma 5.7, compared with other patients investigated for liver disease.

Diagnosis

Diagnosis of antitrypsin deficiency should be considered in any chronic liver disease of uncertain cause in children and adults of white and particularly Northern European populations. The probability of antitrypsin deficiency as a cause of the disease increases in patients with a family history of liver or obstructive lung disease and in patients in whom alcohol or viral hepatitis may be excluded. Children with neonatal hepatitis, giant cell hepatitis, juvenile cirrhosis, or chronically elevated liver chemistry tests should be investigated for antitrypsin phenotype. Adults with chronic active hepatitis lacking serologic markers, or with cryptogenic cirrhosis, with or without hepatoma, also should be evaluated.

The initial discovery of antitrypsin deficiency is usually made by the absence of the alpha-1 peak on serum protein electrophoresis. This method is not very sensitive, and quantitative determination of serum antitrypsin level and protease inhibitor typing is usually necessary for accurate diagnosis. Liver biopsy further supports the diagnosis and helps to stage the extent of liver damage.

Biochemical studies

Plasma antitrypsin levels may be determined in most clinical laboratories by electroimmunoassay. Plasma levels should be related to the normal reference range for each laboratory. Functional analysis may also be performed by determination of total trypsin inhibitory capacity, 90% of which is due to antitrypsin activity. Discrepancies may occur between immunologic and functional analyses due to the presence of dysfunctional or inactive species. Subnormal levels suggest a genetic antitrypsin variant and are only rarely secondary to a disease process.

Low levels have been described, however, in the infant respiratory distress syndrome, in protein-losing states, and in terminal liver failure. Levels below 20% of normal suggest the homozygous deficiencies protease inhibitor Z, protease inhibitor M malton, protease inhibitor M Duarte, and protease inhibitor null, or heterozygous combinations of these alleles. Levels in the range 40% to 70% are compatible with heterozygous deficiency (protease inhibitor MO, SZ, MZ, etc.). Heterozygotes with liver disease or active inflammation may well exhibit normal levels.

Phenotype determination

Isoelectric focusing is the method of choice for phenotyping. A monoclonal antibody specific for protease inhibitor Z antitrypsin has been developed and is useful in detecting the presence of the protease inhibitor Z allele. It has been used for mass population screening in an enzyme-linked immunosorbent assay. Such antibodies also may be used for specific staining of histologic material.

Specific diagnosis of most phenotypes also may be performed at the deoxyribonucleic acid level. Some genetic mutations may be identified by Southern blotting due to their fortuitous localization at a restriction endonuclease site (restriction fragment length polymorphism). This method may be performed on deoxyribonucleic acid purified from very few cells and therefore is ideally suited to prenatal diagnosis.

Liver biopsy and histopathology

О±₁-antitrypsin globular inclusions are localized predominantly in periportal hepatocytes, are weakly acidophilic, and may be overlooked easily on routine hematoxylin-eosin sections. After diastase treatment to remove glycogen, the remaining immature glycoprotein is strongly periodic acid – Schiff-positive, reflecting high mannose content. In general, the number and size of globules increase with age and disease activity. Globules may be missed entirely in liver biopsies from heterozygotes due to sampling error.

Immunofluorescence and immunoperoxidase staining with nonspecific antisera against antitrypsin are more sensitive than periodic acid – Schiff-D staining for the detection of intrahepatocellular aggregates. These techniques can be applied to both frozen and formalin-fixed tissue. Electron microscopy can reveal antitrypsin, in the endoplasmic reticulum (endoplasmic reticulum), with dilatation in other periportal hepatocytes in which biosynthesis generally predominates, in both hetero- and homozygotes.

Adult liver disease in antitrypsin deficiency is usually characterized by relatively low-grade inflammation radiating from portal tracts. Inflammatory cells (primarily lymphocytes) are distributed in close proximity to areas of abundant periodic acid – Schiff-D globules. There may be piecemeal necrosis. As the disease progresses, the liver becomes more fibrotic with the development of macronodular cirrhosis. Hepatoma of a hepatocellular or cholangiocellular type may accompany the cirrhosis.

Treatment

• Prevention. As in all genetic disease, the diagnosis of alpha¹-antitrypsin deficiency in a patient, regardless of the mode of clinical presentation (lung, liver, or other symptoms), should lead to investigations of the family. It is desirable to identify homozygotes in an asymptomatic stage. Patients should be advised against smoking. Genetic counseling should be provided to families with one or more children affected by liver disease.
• Medical therapy. No medical therapy is beneficial in patients with liver disease.
• Liver transplantation. Liver transplantation provides a new source of plasma antitrypsin. In these patients, the protease inhibitor typing converts to that of the donor. The 1-year survival is 90% and the 5-year survival of juvenile patients in most transplant centers is 80% to 85%. The experience of liver transplantation for cirrhosis in protease inhibitor Z adults is limited. In the absence of serious pulmonary manifestations, indications for liver transplantation are essentially those for decompensation due to chronic liver disease of any cause. Preoperative evaluation of pulmonary function and the exclusion of hepatoma are essential.