Fibrocystic liver disease refers to a heterogeneous group of disorders with shared, but also distinct, pathophysiologic and clinical features. Cystic dilatation of intrahepatic bile duct structures and variable degrees of portal fibrosis are the hallmarks of fibrocystic liver disease. In many instances, there are morphologic abnormalities in the kidneys that parallel those of the liver. It has been recognized for centuries that hepatic and renal cysts are seen in the same individuals [1], although it has not always been accepted that they are manifestations of the same diseases. The older literature contains confusing descriptive classifications of fibrocystic diseases, with imprecise and overlapping definitions. Even now, attempts at describing clinical and radiographic features, prognosis, natural history, and treatment are somewhat hampered by reliance on these descriptive reports. However, much of the molecular basis for these disorders has been elucidated, and clinical diagnoses are being modified using more exact genetic criteria. The current consensus is that genetic determinants of differentiation and development of renal tubules and biliary structures result in a broad spectrum of congenital abnormalities grouped under the heading of fibrocystic liver and kidney disease.

The liver attains its highest relative size at about 10% of fetal weight at the ninth week of gestation. Early in gestation the liver is the primary site for hematopoiesis. At seven weeks of gestation, hematopoietic cells outnumber hepatocytes. Primitive hepatocytes are smaller than mature cells and are deficient in glycogen. As the fetus nears term, hepatocytes predominate and enlarge with expansion of the endoplasmic reticulum and accumulation of glycogen. Hepatic blood flow, plasma protein binding, and intrinsic clearance by the liver (reflected in the maximal enzymatic and transport capacity of the liver) also undergo significant postnatal maturation. These changes correlate with an increased capacity for hepatic metabolism and detoxification. At birth, the liver constitutes about 4% of body weight compared with 2% in the adult. Liver weight doubles by 12 months of age and increases three-fold by three years of age.

When first encountering an infant or child with cholestatic liver disease, it is essential that diagnostic evaluation be conducted promptly in order to recognize disorders amenable either to specific medical therapy (e.g., galactosemia, tyrosinemia, hypothyroidism, urinary tract infection) or to early surgical intervention (e.g., biliary atresia, choledochal cyst); institute treatment directed toward enhancing bile flow; and prevent and treat the varied medical, nutritional, and emotional consequences of chronic liver disease.

Jaundice sometimes appears at birth, indicated by the dark yellow color of the countenance and arising from obstructions of the liver. Cases are generally incurable.

Inherited cholestasis of hepatocellular origin has long been described in the neonate or during the first year of life [1]. Many of these infants were categorized as having idiopathic neonatal hepatitis after biliary atresia, metabolic diseases, and congenital infections were excluded [2]. The prognosis in familial cholestasis was poor compared with sporadic cholestasis that sometimes had an identifiable etiology. As the clinical and genotypic heterogeneity of these inherited disorders has become apparent, it is now recognized that patients may present initially and progress to end-stage liver disease at ages ranging from infancy to adulthood [3, 4].There may be significant overlap in clinical features such as intense pruritus and a low serum concentration of gamma-glutamyltransferase (GGT). The histopathology, immunohistochemical staining, and hepatic ultrastructure may provide additional diagnostic clues as to the underlying defect. However, next generation sequencing including use of targeted gene panels has proven of great value in rapidly and reliably discriminating cholestatic diseases of childhood, may suggest therapy with varying success based on the genotype of the patient, and has advanced our understanding of molecular mechanisms of bile secretion and acquired cholestasis [5]. It is not surprising that, so far, mutations in three genes encoding ATP-dependent transport proteins localized to the canalicular membrane that result in progressive cholestasis and liver injury have been discovered. The features of these disorders are compared in Table 13.1. Other genes encoding proteins involved in membrane transport, vesicular trafficking, and integrity of the cell junction may also be mutated in some patients. Mutations in the genes responsible for PFIC may be found in some adults with cryptogenic cholestasis and women with cholestasis of pregnancy including in the heterozygous state [6]. Owing to an immaturity of hepatic excretory function, cholestasis may occasionally occur in inherited diseases because of systemic illness rather than a primary defect in the liver (see Table 9.1). These disorders will not be considered in this review.

Introduction

Inherited cholestasis of hepatocellular origin has long been described in the neonate or during the first year of life [1]. Many of these infants were categorized as having idiopathic neonatal hepatitis after biliary atresia, metabolic diseases, and congenital infections were excluded [2,3]. The prognosis in familial cholestasis was poor compared with sporadic cholestasis that sometimes had an identifiable etiology. As the clinical and genotypic heterogeneity of these inherited disorders has become apparent, it is now recognized that patients may present initially and progress to end-stage liver disease at ages ranging from infancy to adulthood [4]. There may be significant overlap in clinical features such as intense pruritus and a low serum concentration of gamma-glutamyltransferase (GGT). The histopathology, immunohistochemical staining, and hepatic ultrastructure may provide additional diagnostic clues as to the underlying defect. However, the identification of the genes responsible for several of these disorders now allows a specific diagnosis in many cases, may suggest therapy with varying success based on the genotype of the patient, and has advanced our understanding of molecular mechanisms of bile secretion and acquired cholestasis. It is not surprising that, so far, mutations in three genes encoding ATP-dependent transport proteins localized to the canalicular membrane that result in progressive cholestasis and liver injury have been discovered. The features of these disorders are compared in Table 13.1. Other genes encoding proteins involved in membrane transport, vesicular trafficking, and integrity of the cell junction may also be mutated in some patients. Owing to an immaturity of hepatic excretory function, cholestasis may occasionally occur in inherited diseases because of systemic illness rather than a primary defect in the liver (see Table 9.1). These disorders will not be considered in this review.