Abetalipoproteinemia

Rare congenital disorder that causes the body to not produce chylomicrons, low-density lipoprotein (LDL), and very-low-density lipoprotein (VLDL). Coagulation disorder, demyelination and ataxia, peripheral sensory neuropathy, retinitis pigmentosa, acanthocytosis, diminished response to local anesthetics.

Bassen-Kornzweig Syndrome; Acanthocytosis; Microsomal Triglyceride Transfer Protein Deficiency.

Unknown. Males are approximately 1.5 times more often affected than females.

Autosomal recessive. Abetalipoproteinemia is caused by mutations in the gene responsible for microsomal triglyceride transfer protein (MTP). MTP is thought to transfer lipids to the apo-β protein as it is translated, allowing it to attain the proper conformation for lipoprotein assembly. Gene locus is on chromosome 4q22-24.

Beta lipoproteins are lipoproteins of various molecular weights, with apo-100 (essential component of VLDL and LDL) and apo-48 (mainly in chylomicrons) as their principal subtypes. These lipoproteins bind to specific receptors on human cells, allowing exchange of lipids. Virtual absence of VLDLs and LDLs results in low levels of plasma cholesterol and triglycerides. However, cholesterol delivery to individual cells remains normal by an increased cholesterol-carrying capacity of the high-density lipoproteins (HDLs). Although the basal cortisol secretion in the adrenal cortex is normal, its maximal rate cannot be reached with corticotropin stimulation.

Based on the clinical course, reduced plasma lipids (electrophoresis), and absent apo-β. A peripheral smear shows 50% acanthocytosis and hyperbilirubinemia (reduced red cell lifespan). Sural nerve biopsy reveals loss of large myelinated fibers.

Age of onset is the first year of life (gastrointestinal manifestations). Within the first 10 years, neurologic and ocular manifestations appear. Fat malabsorption (chronic diarrhea) is severe. Spinocerebellar ataxia, peripheral neuropathy, pigmented retinopathy, and ceroid myopathy are secondary to tocopherol transport defect in the blood. Muscle dysfunction resulting in pes cavus and kyphoscoliosis is common. Fatal cardiomyopathy has been described. Treatment is supportive only with fat-soluble vitamin supplements (A, D, E, K) and tocopherols. Use of triglyceride containing long-chain fatty acids has been attempted.

Evaluate the extent of neurologic deficit. Check pulmonary function with SpO2, FEV1, and forced vital capacity; chest radiograph; arterial blood gas analysis. Laboratory investigations show anemia (resulting from iron and/or folate deficiency, autohemolysis) and prolonged prothrombin time (resulting from vitamin K deficiency, liver cirrhosis) but normal platelet function. Electrolyte changes may be present (because of potential adrenal dysfunction and vomiting and diarrhea as part of the fat malabsorption). Assess cardiac function (ECG, chest radiograph, echocardiogram for ventricular function). Hypoalbuminemia (caloric and protein malnutrition) and reduced α1-acid glycoprotein levels may be present.

A rapid sequence induction technique is indicated in the presence of vomiting. High risk for cardiorespiratory failure in patients with severe lung and cardiac disease. Muscle weakness from myopathy and malnutrition may confound the problem. Regional anesthesia is contraindicated if coagulation is not within the normal range.

Use of succinylcholine can be dangerous if neuropathy or myopathy is present (a fast nondepolarizing neuromuscular agent ...