Primary Biliary Cirrhosis

Causes and origin

PBC is an autoimmune disease process and is often considered a model autoimmune disease because of its signature serology, the antimitochondrial antibody, and specific bile duct pathology. The cause is probably partly genetic and partly environmental: the disease is thought to be environmentally triggered in genetically predisposed individuals. The rate of concordance amongst identical twins is amongst the highest of all autoimmune diseases. Families with a strong family history have been described.

Prevalence

The prevalence of PBC has been estimated as 12.9 per 100,000 population, with up to 90% of cases occurring in women.

PBC is more common amongst those of northern European descent and less common amongst those of African origin.

Diagnosis is usually between about 45 and 55 years old.

Appearance

Background

The diagnosis of PBC should be suspected where chronic cholestasis is found after exclusion of other causes of liver disease.

About 25% of patients with PBC are diagnosed as a result of blood tests taken for other reasons and are asymptomatic at the time.

Fatigue: this is the most common symptom in PBC and occurs in 65-80% and is often the presenting symptom. It appears to be associated with a higher mortality. It does not improve with treatment of depression and its aetiology is unknown.

Right upper quadrant pain or discomfort: occurs in 10-15%.

At a later stage the patient may present with Jaundice of cholestatic origin with dark urine and pale stool.

Sjogren’s syndrome is commonly present, with dry eyes and dry mouth.

Pruritus: around 55% report pruritus and in 10% this is severe. It is usually assumed to be due to deposition of bile pigments in skin.

Investigation

Hepatomegaly occurs in 25%.

Hyperpigmentation occurs in 25%.

Splenomegaly occurs in 15%.

Jaundice occurs in 10%.

Xanthelasma may occur in the later stages.

In advanced disease cirrhosis eventually occurs, with associated features (including ascites, spider naevi and other features of portal hypertension.

Related conditions

There may be other diseases and conditions present, especially those of autoimmune origin. These include:

Thyroid disease

Systemic sclerosis includingits variant of CREST (calcinosis, Raynaud’s phenomenon (o)esophagealmotility disorder, sclerodactyly and telangiectasias).

Coeliac disease

Extrahepatic malignancy.

Hepatocelluar carcinoma

Seropositive arthritis

Seronegative arthritis

Gallstones

Osteoporosis occurs in up to one third of patients. The cause is uncertain, as patients with PBC have normal vitamin D metabolism.

Hyperlipidaemia is seen in many patients

association with hepatocellular carcinoma may be more than for any other form of cirrhosis.

Examinations

FBC is often normal but ESR is elevated.

Abnormal LFTs are usual but not invariable:

Alkaline phosphatase is usually elevated as PBC is a cholestatic condition.

Less consistently, transaminases are raised.

Bilirubin is often normal at first but rises as the disease progresses. Rising bilirubin demonstrates disease progression and heralds liver failure.

Partial thromboplastin time (PTT) and albumin are normal until a late stage.

IgM is raised.

Lipid levels and cholesterol levels are raised in 85% but risk of coronary heart disease (CHD) is not raised as high-density lipoprotein (HDL) cholesterol is elevated.

Autoantibodies are characteristic:

The most specific to PBC are antimitochondrial antibodies (AMAs), present in 90-95% of affected individuals (and 0.5% of normal controls, giving a specificity of over 98%.)

Around 0.5% of the general population is positive for AMAs. Studies suggest that fewer than 10% of patients with positive AMAs will develop PBC, although almost all patients with PBC have positive AMAs.

About 35% also have antinuclear antibodies.

There may also be other auto antibodies, especially related to the thyroid. Thyroid function should be assessed and monitored.

Imaging:

Imaging of the liver is useful to exclude causes of obstruction like stones. Ultrasound is most commonly used but CT and MRI scanning may be employed. As the disease progresses there may be features suggestive of portal hypertension and cirrhosis.

Cholangiography is occasionally helpful in order to exclude primary sclerosing cholangitis. Transient elastography is a non-invasive tool to evaluate the degree of liver Fibrosis

Finally, liver biopsy is required to stage the disease. Histology will demonstrate chronic nonsuppurative cholangitis of the interlobular and septal bile ducts.

Interpretation standards

Diagnosis is based on two of the following three criteria being met:

Biochemical evidence of cholestasis with evidence of alkaline phosphatase activity.

Presence of AMAs.

Histological evidence of nonsuppurative destructive cholangitis and destruction of interlobular bile ducts.

Distinct phases

Portal stage with portal inflammation and bile duct abnormalities.

Periportal stage with periportal fibrosis, with or without periportal inflammation.

Septal stage with septal fibrosis and active inflammation.

Cirrhotic stage with nodules with various degrees of inflammation.

The Mayo Risk Score is a tool which stratifies prognosis in PBC using aspartate aminotransferase (AST), albumin and the presence of variceal bleeding. ^[19]

Distinguished interpretation

Autoimmune hepatitis

Reaction to phenothiazines

Sarcoidosis

Doctoring

Treatments are aimed at alleviation of symptoms and at slowing the disease. Measuring outcomes can be difficult. Only liver transplantation offers a cure but the disease can recur in the transplanted liver.

Fatigue is a very common symptom and has an adverse effect on quality of life. It is difficult to treat. Modafinil has shown promise in this area, and trials suggest it produces benefits in energy, somnolence and sleep requirements. Modafinil has been proposed as a possible treatment. Pruritus may be treated with sedating antihistamines in the early stages but later colestyramine or colestipol are used. They sequester bile salts but it takes between one and four days before there is any effect. Again it is a very difficult symptom to treat.

Rifampicin has helped some patients unresponsive to colestyramine but its mode of action is unknown. Plasmapheresis is also effective. However, for severe, intractable pruritus a liver transplant offers the only hope.

Ursodeoxycholic acid (UDCA) slows progression of the disease. Patients with early disease have clinical, biochemical, and histological improvement but its value in late disease is dubious.

Drugs are used to inhibit the autoimmune process:

Methotrexate is well established although its basis has been criticised as anecdotal rather than based on randomised controlled trials.

Steroids may help but osteoporosis is a concern.

Ciclosporin may be beneficial. However, it is recommended that it should only be used in the context of a clinical trial. It has a high rate of complications, such as renal dysfunction and hypertension.

Azathioprine was recommended after a large international trial in 1985 showed beneficial effects and few adverse effects.

D-penicillamine does not appear to reduce morbidity or mortality.

Oestrogens promote cholestasis and so combined oral contraceptives and HRT should be avoided. Pregnant women with PBC may develop worsening itching which does not fully resolve after pregnancy. They should be assessed during pregnancy for the presence of varices due to the marked blood volume increase during pregnancy. Treatment with beta-blockers is safe in pregnancy and prolonged pushing is to be avoided.

As liver failure sets in, a transplant offers the only hope for cure. Increasing prothrombin time, elevated bilirubin and decreased albumin all point to the time being due. After two to five years from the transplant, between 8% and 16% will have recurrence of the disease, as the underlying autoimmune process remains. This figure may rise to 50% by 10 years. There also tend to be more problems of chronic rejection than with other indications for transplantation.

Intricacies

Renal tubular acidosis occurs in around half of patients with PBC. Copper deposition in the renal tubules or an autoimmune phenomenon may be the mechanism.

Around 20% develop hypothyroidism

Hepatocellular carcinoma– develops in about 6% but this represents about 4% of women with the disease and 20% of men. Regular screening for the condition is advised for all patients with cirrhosis.

There may be malabsorption of fats with steatorrhoea and fat-soluble vitamin deficiency

outlook

The prognosis of PBC has improved considerably in recent years. This is because of both earlier diagnosis (and particularly a recognition of asymptomatic, indolent cases) and probably because of use of UDCA).

New indicators of prognosis will be useful particularly for the increasing number of patients with less severe disease. The relatively poor figures for prognosis quoted before recent trends in early diagnosis can be both alarming and misleading.

One study suggests that the median time from the first positive AMA test to persistently abnormal LFTs is six years, with a range of 1-19 years.

None of the patients in this study developed cirrhosis during follow-up and the study was small.

This remains a serious disease and a worrying diagnosis. Affected patients will need information and support. Ten-year survival of asymptomatic patients in three studies ranged from 50-70%, whereas median duration of survival from the onset of symptoms ranged from 5-8 years.

Liver transplantation in PBC

The outcome of liver transplantation for patients with PBC is more favourable than for nearly all other disease categories.

Liver transplantation improves fatigue, pruritus, and Sjögren’s syndrome. Bone disease worsens initially but then improves. AMA may persist or reappear but does not in itself signify a recurrence of PBC.

CONCLUSION

Primary biliary cirrhosis (PBC) is a slowly progressive autoimmune disease of the biliary system with a chronic course which may extend over many decades. It involves destruction of the small interlobular bile ducts (canals of Hering). This causes intrahepatic cholestasis which damages cells, leading to scarring, fibrosis and eventually cirrhosis. It is an insidious disease which progresses through the clinical phases: preclinical, asymptomatic, symptomatic, and finally liver insufficiency (liver failure). The prognosis has improved significantly over a period of two decades because of earlier diagnosis and effective treatment which, whilst not curative, significantly slows progression if started in the early stages, and often does so sufficiently to allow a normal lifespan.