Glycogen storage disease VII is an autosomal recessive metabolic disorder characterized clinically by exercise intolerance, muscle cramping, exertional myopathy, and compensated hemolysis. Myoglobinuria may also occur. The deficiency of the muscle isoform of PFK results in a total and partial loss of muscle and red cell PFK activity, respectively. Raben and Sherman (1995) noted that not all patients with GSD VII seek medical care because in some cases it is a relatively mild disorder.

Polycystic liver disease-1 is an autosomal dominant condition characterized by the presence of multiple liver cysts of biliary epithelial origin. Although the clinical presentation and histologic features of polycystic liver disease in the presence or absence of autosomal dominant polycystic kidney disease (see, e.g., PKD1, 173900) are indistinguishable, PCLD1 is a genetically distinct form of isolated polycystic liver disease (summary by Reynolds et al., 2000). A subset of patients (28-35%) may develop kidney cysts that are usually incidental findings and do not result in clinically significant renal disease (review by Cnossen and Drenth, 2014). Genetic Heterogeneity of Polycystic Liver Disease See also PCLD2 (617004), caused by mutation in the SEC63 gene (608648) on chromosome 6q21; PCLD3 (617874), caused by mutation in the ALG8 gene (608103) on chromosome 11p; and PCLD4 (617875), causes by mutation in the LRP5 gene (603506) on chromosome 11q13.

Carnitine palmitoyltransferase II (CPT II) deficiency is a disorder of long-chain fatty-acid oxidation. The three clinical presentations are lethal neonatal form, severe infantile hepatocardiomuscular form, and myopathic form (which is usually mild and can manifest from infancy to adulthood). While the former two are severe multisystemic diseases characterized by liver failure with hypoketotic hypoglycemia, cardiomyopathy, seizures, and early death, the latter is characterized by exercise-induced muscle pain and weakness, sometimes associated with myoglobinuria. The myopathic form of CPT II deficiency is the most common disorder of lipid metabolism affecting skeletal muscle and the most frequent cause of hereditary myoglobinuria. Males are more likely to be affected than females.

Familial hemophagocytic lymphohistiocytosis-2 (FHL2) is an autosomal recessive disorder of immune dysregulation with onset in infancy or early childhood. It is characterized clinically by fever, edema, hepatosplenomegaly, and liver dysfunction. Neurologic impairment, seizures, and ataxia are frequent. Laboratory studies show pancytopenia, coagulation abnormalities, hypofibrinogenemia, and hypertriglyceridemia. There is increased production of cytokines, such as gamma-interferon (IFNG; 147570) and TNF-alpha (191160), by hyperactivation and proliferation of T cells and macrophages. Activity of cytotoxic T cells and NK cells is reduced, consistent with a defect in cellular cytotoxicity. Bone marrow, lymph nodes, spleen, and liver show features of hemophagocytosis. Chemotherapy and/or immunosuppressant therapy may result in symptomatic remission, but the disorder is fatal without bone marrow transplantation (summary by Dufourcq-Lagelouse et al., 1999, Stepp et al., 1999, and Molleran Lee et al., 2004). For a general phenotypic description and a discussion of genetic heterogeneity of FHL, see 267700.

Lipoyl transferase 1 deficiency is a very rare inborn error of metabolism disorder, with a highly variable phenotype, typically characterized by neonatal to infancy-onset of seizures, psychomotor delay, and abnormal muscle tone that may include hypo- and/or hypertonia, resulting in generalized weakness, dystonic movements, and/or progressive respiratory distress, associated with severe lactic acidosis and elevated lactate, ketoglutarate and 2-oxoacids in urine. Additional manifestations may include dehydration, vomiting, signs of liver dysfunction, extrapyramidal signs, spastic tetraparesis, brisk deep tendon reflexes, speech impairment, swallowing difficulties, and pulmonary hypertension.

Biliary atresia is a disorder of infants in which there is progressive obliteration or discontinuity of the extrahepatic biliary system, resulting in obstruction of bile flow. Untreated, the resulting cholestasis leads to progressive conjugated hyperbilirubinemia, cirrhosis, and hepatic failure (Bates et al., 1998). Most patients require liver transplantation within the first year of life (Leyva-Vega et al., 2010). See also Alagille syndrome (118450), which includes biliary atresia as a feature.

Familial Hemophagocytic lymphohistiocytosis (FHL) is a rare primary immunodeficiency characterized by a macrophage activation syndrome with an onset usually occurring within a few months or less common several years after birth.

Progressive familial intrahepatic cholestasis-10 (PFIC10) is an autosomal recessive liver disorder characterized by the onset of symptoms in the first months or years of life. Features include jaundice, pruritis, and hepatomegaly associated with increased serum bilirubin and bile acids. Liver transaminases may be variably increased, but gamma-glutamyltransferase (GGT; see 612346) is normal. Liver biopsy shows hepatocellular and canalicular cholestasis with giant cell changes. Although rare patients may have episodes of diarrhea and even show endoscopic features of microvillus inclusion disease (MVID), this tends to be transient and cholestasis dominates the clinical picture (Gonzales et al., 2017; Cockar et al., 2020). For a discussion of genetic heterogeneity of progressive familial intrahepatic cholestasis, see PFIC1 (211600).