Vitamin E and oxidative stress in abetalipoproteinemia and familial hypobetalipoproteinemia

Abetalipoproteinemia (ABL) and familial hypobetalipoproteinemia (FHBL) are genetic diseases characterized by low density lipoprotein deficiency. ABL presents early in life with the gastroenterological manifestations of fat malabsorption, steatorrhea, and failure to thrive, and later in life, with progressive ophthalmopathy and neuropathy as a result of deficiency of the fat-soluble vitamins A and E. Heterozygous FHBL subjects are usually asymptomatic, but may develop fatty liver disease. In homozygous (compound heterozygous) FHBL, the clinical and biochemical features are indistinguishable from those of ABL and treatment recommendations are the same: dietary fat restriction to prevent steatorrhea, and long-term high-dose vitamin E and A supplementation to prevent or at least slow the progression of neuromuscular and retinal degenerative disease. Despite their low plasma vitamin E levels, individuals with heterozygous FHBL do not require vitamin E supplementation. There are conflicting reports on whether increased oxidative stress is seen in ABL; these differences may relate to the small size of patient groups as well as differences in patient age and dose of vitamin E supplementation, or the contribution from dietary sources of vitamin E. High density lipoproteins in ABL appear to be severely oxidized yet able to inhibit platelet aggregation by binding to scavenger receptor B1. We review the role of vitamin E and oxidative stress in ABL and FHBL.

Clinical features and molecular genetics of autosomal recessive cerebellar ataxias

Among the hereditary ataxias, autosomal recessive spinocerebellar ataxias comprise a diverse group of neurodegenerative disorders. Clinical phenotypes vary from predominantly cerebellar syndromes to sensorimotor neuropathy, ophthalmological disturbances, involuntary movements, seizures, cognitive dysfunction, skeletal anomalies, and cutaneous disorders, among others. Molecular pathogenesis also ranges from disorders of mitochondrial or cellular metabolism to impairments of DNA repair or RNA processing functions. Diagnosis can be improved by a systematic approach to the categorisation of these disorders, which is used to direct further, more specific, biochemical and genetic investigations. In this Review, we discuss the clinical characteristics and molecular genetics of the more common autosomal recessive ataxias and provide a framework for assessment and differential diagnosis of patients with these disorders.

[An adult case of probable Bassen-Kornzweig syndrome, presenting resting tremor]

We report a 53-year-old woman with probable Bassen-Kornzweig syndrome. Her parents were a consanguineous marriage. At two years of age, she developed night blindness. During her childhood she had severe diarrhea that disappeared in adulthood. At 26 years of age, she was diagnosed as having retinitis pigmentosa and her visual acuity became worse thereafter. She noted tremor in the right hand at 37 years of age, gait ataxia at 42, and developed tremor in the bilateral lower extremities at 48. On admission, bilateral visual disturbance, resting and postural tremor, moderately poor coordination, mild distal dominant sensory impairment, an absence of tendon reflex in all four extremities, moderate to severe gait ataxia, and positive Romberg sign were found. Muscle rigidity and akinesia were not observed. Intelligence and muscle power were normal and pathological reflexes were absent. Acanthocytes were found in blood. Serum chemistry showed remarkable decreases in total cholesterol (54 mg/dl, normal 180-220), triglyceride (0 mg/dl, normal 30-150), beta-lipoprotein (3 mg/dl, normal 190-500), apoA-1 protein (66 mg/dl, normal 105-184), apoA-2 protein (11 mg/dl, normal 26-46), apoB protein (0 mg/dl, normal 38-104), apoC-2 protein (1.1 mg/dl, normal 1.2-6.4), vitamin A (297 ng/ml, normal 431-1,041), and vitamin E (0.19 ng/dl, normal 0.75-1.41). While, a marked increase in PIVKA II (703 mAU/ml, normal<40) due to a decrease in vitamin K was found. She was thus diagnosed as having Bassen-Kornzweig syndrome or hypo-betalipoproteinemia. Although brain MRI was normal, single-photon emission CT (SPECT) showed mildly decreased perfusion in the left parietal cortex and right striatum. Motor nerve conduction velocities were normal, but sensory nerve action potentials were not evoked in all four extremities. Surface EMG recorded on the right radial extensor and flexor carpi muscles at rest showed a 4.5 Hz tremor. Vitamin replacement therapy with vitamin A (10,000 IU/day), E (200 mg/day), and K (10 mg/day) was initiated. Several days after treatment, amplitude of resting tremor ameliorated mildly. Clonazepam was administered (0.5 mg/day) for further treatment. After one-month of treatment, vitamin A (656 ng/ml) and E (0.39 mg/dl) levels were elevated and PIVKA II level (29 mAU/ml) decreased. Only a mild right hand tremor remained, but sensory impairment and gait ataxia were not changed. The cause of Bassen-Kornzweig syndrome is a deletion of the microsomal triglyceride transfer protein (MTP) gene. While, familial hypo-betalipoproteinemia, due to a mutation of apolipoprotein B gene, is known to show the same phenotype. Because of the patient's refusal of genetic examination, which disease she has cannot be conclusively determined. Intention tremor was reported in Bassen-Kornzweig syndrome. However, her 4.5 Hz tremor was also present at rest, which resembled resting tremor in Parkinson's disease. Pathophysiology of Bassen-Kornzweig syndrome is known to be due to hypo-vitaminosis. Decreased [18F]-dopa uptake in striatum of patients with long-term hypo-vitamin E has been reported in PET study. Mild hypoperfusion was found in the striatum of the present cases: indicating that her tremor was associated with striatonigral damage. Thus, careful observation of extrapyramidal signs is necessary in abeta- or hypo-betalipoproteinemia.

Mutations in MTP gene in abeta- and hypobeta-lipoproteinemia

Familial hypobetalipoproteinemia (FHBL) and abetalipoproteinemia (ABL) are inherited disorders of apolipoprotein B (apo B)-containing lipoproteins that result from mutations in apo B and microsomal triglyceride transfer protein (MTP) genes, respectively. Here we report three patients with severe deficiency of plasma low-density lipoprotein (LDL) and apo B. Two of them (probands F.A. and P.E.) had clinical and biochemical phenotype consistent with ABL. Proband F.A. was homozygous for a minute deletion/insertion (c.1228delCCCinsT) in exon 9 of MTP gene predicted to cause a truncated MTP protein of 412 amino acids. Proband P. E. was heterozygous for a mutation in intron 9 (IVS9-1G>A), previously reported in an ABL patient. We failed to find the second pathogenic mutation in MTP gene of this patient. No mutations were found in apo B gene. The third proband (D.F.) had a less severe lipoprotein phenotype which was similar to that of heterozygous FHBL and appeared to be inherited as a co-dominant trait. However, he had no mutations in apo B gene. He was found to be a compound heterozygote for two missense mutations (D384A and G661A), involving highly conserved regions of MTP. Since this proband was also homozygous for varepsilon2 allele of apolipoprotein E (apo E), it is likely that his hypobetalipoproteinemia derives from a combined effect of a mild MTP deficiency and homozygosity for apo E2 isoform.

Endocrine function in abetalipoproteinemia: a study of a female patient of Greek origin

AIM

To investigate the pituary, genitalia, adrenal, thyroid, parathyroid and pancreatic endocrine function of a female patient aged 37 with abetalipoproteinemia at the time of diagnosis and 5 years thereafter (after application of a modified diet). SUBJECT-METHODS: Serum concentrations of cortisol, A4, ACTH, aldosteron, renin, dehydroepiandrosterone sulfate (DHEA-5), progesterone, 17-OH progesterone, testosterone, SH13G, estradiol, luteinizing hormone, follicle stimulating hormone, T3, T4, TSH, FT3, FT4, parathormone, osteocalcin, prolactin, proinsuline, insulin, glucagon, somatomedin-C (Insulin-like Growth Factor-1, IGF-1), IG171-13P3, 25 (OH) Vitamin D3 and 1-25 (OH) 2 Vitamin D3, were measured by radioimmunoassay. Synactlien test, and 24-hour urine cortisol, were also estimated. Serum leptin estimation was carried-out using a sensitive enzymatic technique. Ionized part of serum calcium was measured by the use of a special machine (CORNING), while bone alkaline phosphatase was measured by radioimmunoassay.

RESULTS

Serum progesterone and 17-OH-progesterone were reduced in both examinations. Estimation of serum progesterone performed on the 21th day of the menstrual cycle revealed again values below the lowest normal limit. Serum prolactin was increased both in rest and during movement. The levels of both, somatomedin-C (IGF-1) and leptin were below the lowest normal limit. Despite normal serum parathormone, serum-ionized calcium and 25-OH vitamin D were low, while serum bone alkaline phosphatase was increased. Serum proinsulin was increased, and serum insulin was low. Serum thyroid hormone, glucagon, parathormone, FSH, LH, ACTH, testosterone, estradiol and SH13G were normal. The hormonal profile of the patient estimated 5 years later did not differ substantially suggesting that the metabolic improvement due to the adoption of the modified diet had not any significant impact on it.

CONCLUSION

Female patients with abetalipoproteinernia have reduced production of progesterone by the corpus luteum and slightly abnormal bone metabolism. The reduced production of progesterone is probably due to the low levels of serum LDL and cholesterol, while reduced serum levels of Leptin and IG17-1 are probably due to the impairment nutritional status. The adoption of a modified diet does not alter the hormonal profile significantly.

CD1d function is regulated by microsomal triglyceride transfer protein

CD1d is a major histocompatibility complex (MHC) class I-related molecule that functions in glycolipid antigen presentation to distinct subsets of T cells that express natural killer receptors and an invariant T-cell receptor-alpha chain (invariant NKT cells). The acquisition of glycolipid antigens by CD1d occurs, in part, in endosomes through the function of resident lipid transfer proteins, namely saposins. Here we show that microsomal triglyceride transfer protein (MTP), a protein that resides in the endoplasmic reticulum of hepatocytes and intestinal epithelial cells (IECs) and is essential for lipidation of apolipoprotein B, associates with CD1d in hepatocytes. Hepatocytes from animals in which Mttp (the gene encoding MTP) has been conditionally deleted, and IECs in which Mttp gene products have been silenced, are unable to activate invariant NKT cells. Conditional deletion of the Mttp gene in hepatocytes is associated with a redistribution of CD1d expression, and Mttp-deleted mice are resistant to immunopathologies associated with invariant NKT cell-mediated hepatitis and colitis. These studies indicate that the CD1d-regulating function of MTP in the endoplasmic reticulum is complementary to that of the saposins in endosomes in vivo.

Clinical features and molecular bases of neuroacanthocytosis

The term acanthocytosis is derived from the Greek for "thorn" and is used to describe a peculiar spiky appearance of erythrocytes. Acanthocytosis is found to be associated with at least three hereditary neurological disorders that are generally referred to as neuroacanthocytosis. Abetalipoproteinaemia is an autosomal recessive condition, characterised by absence of serum apolipoprotein B containing lipoproteins leading to fat intolerance and fat-soluble vitamin deficiency. This results in a progressive spinocerebellar ataxia with peripheral neuropathy and retinitis pigmentosa. Chorea-acanthocytosis is also an autosomal recessive condition and is characterised by chorea, orofaciolingual dyskinesia, dysphagia, dysarthria, areflexia, seizures and dementia. Some of its features, including choreic movements, peripheral neuropathy with areflexia, elevated serum creatine kinase levels and myopathy are shared by another form of neuroacanthocytosis, McLeod syndrome. Patients affected by this X-linked disorder also show abnormal expression of Kell blood group antigens and a permanent haemolytic state. In addition to these cases, acanthocytosis is occasionally associated with other neurological disorders, such as Hallervorden-Spatz disease. For each of the neuroacanthocytosis syndromes we review the main clinical features and their molecular bases. The recent molecular genetics findings are the first step towards the understanding of the pathogenetic mechanisms and eventually the search for effective treatments.

Acanthocytosis and neurological disorders

Acanthocytosis occurs because of ultrastructural abnormalities of the erythrocyte membranous skeleton resulting in reduced membrane fluidity. At least three hereditary neurological conditions are associated with it, although as yet the pathogenesis of the neurological features is unknown. In abetalipoproteinaemia, an autosomal recessive condition, vitamin E deficiency results in a progressive spinocerebellar syndrome associated with peripheral neuropathy and retinitis pigmentosa. Neuroacanthocytosis is also probably an autosomal recessive condition and is characterised by chorea, orofaciolingual dyskinesia, dysarthria, areflexia, seizures and dementia. McLeod syndrome is an X-linked recessive disorder usually presenting in males as a benign myopathy with areflexia, in association with a particular abnormality of expression of Kell blood group antigens. However, occasionally the neurological features are more severe and indistinguishable from those of neuroacanthocytosis. Recent advances in molecular genetics may assist better understanding of the disease mechanisms and the search for more effective treatments.

Very low activated factor VII and reduced factor VII antigen in familial abetalipoproteinaemia

Abetalipoproteinaemia is a rare disorder of apolipoprotein B metabolism associated with extremely low plasma concentrations of triglyceride. To discover whether the general positive association between factor VII and triglyceride levels extends to this condition, 5 patients were compared with 18 controls. All patients had a triglyceride below 100 micromol/l. Plasma unesterified fatty acid concentration was normal. Although factor IX activity was only slightly reduced (mean 88% standard) and factor IX antigen was normal, mean activated factor VII in patients was strikingly reduced to 34% of that in controls, a level similar to that found in haemophilia B. The patients' mean factor VII activity and factor VII antigen were also significantly reduced to 54% and 63% of those in controls, respectively. Mean factor XI activity and tissue factor pathway inhibitor activity were reduced in patients to 70% and 75% of control values respectively, while factor XII, factor XI antigen, factor X, prothrombin and protein C were normal.

The use of a highly informative CA repeat polymorphism within the abetalipoproteinaemia locus (4q22-24)

Abetalipoproteinaemia is a rare autosomal-recessive disorder caused by a defect in the large subunit of the microsomal triglyceride transfer protein (MTP) which is required for the assembly and secretion of apolipoprotein B-containing lipoproteins. We report here the use of a polymorphic CA dinucleotide repeat in intron 10, MTPIVS10, of the large subunit of the human MTP protein in the analysis of a pregnancy in a consanguineous family, in which abetalipoproteinaemia was suspected, although prenatal diagnosis was subsequently refused. The mutation in the family has been identified as a novel four-nucleotide insertion/duplication of exon 17 between nucleotides 2349 and 2350 of the cDNA sequence of the MTP gene. However, the marker, MTPIVS10, can be used as an alternative to the time-consuming mutation detection techniques.

Effect of decreased plasma low-density lipoprotein levels on adrenal and testicular function in man

OBJECTIVE

The study assessed whether serum LDL cholesterol levels affect adrenal and Leydig cell function in man.

DESIGN AND METHODS

A 24-h continuous ACTH infusion was performed in 15 consecutive chronically ill patients. Serum cortisol and DHEA-s were measured at baseline and at 3, 6, 12, 20, and 24 h during the infusion. Fasting serum lipoprotein levels including LDL cholesterol, HDL cholesterol as well as FSH, LH, total and free testosterone concentrations were also measured on the baseline morning samples prior to the infusion.

RESULTS

The initial 3 and 6 h percent rise in cortisol values during 24 h ACTH infusion were significantly diminished in patients with LDL-C values < 1.55 mmol/L as compared with patients with higher LDL-C levels (127 +/- 17% (SE) vs. 199 +/- 31% (SE); p < 0.02 and 115 +/- 17% vs. 213 +/- 32%; p < 0.02. However, the 24-h areas of cortisol under the curve were comparable in the 2 groups. Basal and ACTH stimulated DHEA-s levels and percent increases tended to be lower in the low LDL-C group but the differences were not statistically significant. The mean total testosterone was lower in the low LDL-C group (5.30 +/- 1.78 vs. 15.60 +/- 1.95 nmol/L; p < 0.0005). Free testosterone levels were also lower in the low LDL-C group (0.03 +/- 0.009 nmol/L vs. 0.08 +/- 0.01 nmol/L; p < 0.001). Five of six patients with low LDL-cholesterol had low testosterone values, but variable LH levels.

CONCLUSIONS

Our results suggest that severe acquired LDL cholesterol insufficiency impairs slightly the initial glucocorticoid response to ACTH stimulation but not the overall cortisol production during sustained ACTH stimulation. It also may contribute to the reduction in testosterone seen in chronically ill patients.

Abetalipoproteinemia. New insights into lipoprotein assembly and vitamin E metabolism from a rare genetic disease

Abetalipoproteinemia is a rare genetic disease that has provided important new insights into the physiology of lipoprotein assembly and vitamin E metabolism. Forty-two years after its initial description, a molecular etiology of ABL has been reported to be a deficiency of a microsomal transfer protein, thus suggesting that this protein plays a key role in lipoprotein particle assembly and secretion both in the intestine and in the liver. Furthermore, studies in patients with ABL have established the critical role of hepatic secretion of VLDL in the delivery of vitamin E to peripheral tissues and the essential role of vitamin E in the maintenance of normal physiological function of multiple tissues. The systematic investigation of this rare genetic disease has provided insights that have substantially enhanced our understanding of human physiology.

Platelet and neutrophil function and eicosanoid release in a subject with abetalipoproteinaemia

It has been suggested that plasma low density lipoprotein (LDL) may affect platelet and leukocyte activity and the release of biologically active eicosanoids which may contribute to the pathogenesis of coronary heart disease. To evaluate the possible biological effects of LDL further we have studied platelet aggregation, leukocyte function and eicosanoid release in a young woman with abetalipoproteinaemia (ABL) who totally lacks LDL. The subject showed decreased platelet response to threshold doses of ADP, collagen and arachidonic acid compared to a matched control measured in parallel or to a larger control group of 22 normal subjects. Aggregation was normal to higher doses of the same agonists. Thromboxane formation in clotted whole blood and in PRP stimulated with collagen was lower for the ABL subject than the control group. Neutrophil function assessed by chemiluminescence following stimulation with PMA, zymosan and FMLP was normal for the ABL subject, although the release of leukotriene B4 from calcium ionophore stimulated cells less than controls. Neutrophil platelet activating factor (PAF) formation and half life in plasma was not altered in ABL. The fatty acid composition of plasma, platelet and erythrocyte membrane phospholipids showed particularly low levels of linoleic acid in ABL compared to controls. Platelet phospholipids from the ABL subject also showed low levels of arachidonic acid. The decrease in eicosanoid formation seen in ABL may be the result of altered fatty acid composition of cell membrane phospholipids, or perhaps a defect in arachidonate mobilization. These results indicate that in a subject who lacks circulating LDL the behaviour of platelets and neutrophils in some in vitro tests is altered, although the extent to which these effects are reflected in vivo with regard to inflammatory and thrombotic mechanisms is not known.

Evoked potential abnormalities in children with chronic cholestasis

To assess the effect of chronic cholestasis and vitamin E deficiency on nervous system function, we did multimodality evoked potential testing of 17 children (mean age = 47 months) who had chronic liver disease. Evoked potential testing was repeated periodically in 11 patients 1 to 33 months after the initial study. Eight children had abnormal delays of the P100 peak of the visual evoked potential, and these children each had significantly higher total serum bile acid levels than did children who had normal visual evoked potentials (p = 0.002). Bilateral brainstem auditory evoked potential abnormalities consistent with conductive hearing losses were initially present in six patients. However, persistent conductive losses were found in four patients, all of whom had arteriohepatic dysplasia. Four children had mildly abnormal somatosensory evoked potentials that were due solely to a mild peripheral neuropathy. Biochemical measures of vitamin E status were not consistently associated with either normal or abnormal visual, brainstem auditory or somatosensory evoked potentials or a combination of evoked potential abnormalities, and an abnormality of one evoked potential type was not associated with an abnormality of any other. A similar lack of relationship between evoked potential results and plasma vitamin A measurement was noted. Following marked improvement in or resolution of cholestasis in four patients, the visual evoked potential became normal, but other evoked potentials did not change. Visual evoked potential improvement was greatest in two patients who underwent orthotopic liver transplantation. This is the first report that demonstrates frequent, potentially reversible visual system abnormalities that are associated with cholestasis and cannot be attributed solely to vitamin E and/or A deficiency.(ABSTRACT TRUNCATED AT 250 WORDS)

[Role of the electrophysiologic examination in the diagnosis of Bassen-Kornzweig syndrome]

An autosomal recessive disorder, abetalipoproteinemia or Bassen-Kornzweig disease, concerning two sisters are described. This disorder, clinically similar to Friedreich ataxia, should be examined by electrophysiological and laboratory procedures because of the possibility of treatment by high doses of vitamin A and E. The routine electrophysiological examination of the two sisters revealed a degenerative spinocerebellar and peripheral nervous process which confirmed the damage of large myelinated fibers, as reported in the literature: neurogenic muscular atrophy of distal muscles, polyphasic motor unit potentials, moderately decrease of lower motor and sensory nerve conduction rates, and reduced amplitude of evoked responses in sensory nerves and muscles. We stress out the diagnostic value of the heterogenous conduction decrease in the distal motor fibers, signs of processes of demyelination or distal regeneration.

Abetalipoproteinemia or Bassen-Kornzweig syndrome. Clinical, biochemical and electrophysiological features of two cases

The clinical, biochemical and electrophysiologic features of two patients with abetalipoproteinemia, a 17 year old boy and his sister of 14, are reported. They are the second and third reports of this disease in Belgium. Diagnosis was made by the Apo-B deficiency in their serum and the normal levels in their parents'. According to other investigators we revealed in both cases deficiency of other apoproteins, indicating, that the metabolic defect affects all classes of plasma lipoproteins. EMG findings showed axonal neuropathy. Somatosensory evoked potentials demonstrated dorsal column dysfunction. Findings were consistent with the known neuropathology of abetalipoproteinemia and of vitamin E deficiency syndromes. The therapeutic role of vitamin E is discussed.

Electrophysiologic features of abetalipoproteinemia: functional consequences of vitamin E deficiency

We performed electrophysiologic testing in 10 patients with abetalipoproteinemia (ABL). Peripheral nerve studies implied an axonal disorder. Visual evoked potentials demonstrated prolonged P100 latency in three patients and abnormal electroretinograms in six. Somatosensory evoked potentials indicated dorsal column dysfunction in eight patients. Brainstem auditory evoked potentials were normal. Findings were consistent with the known neuropathology of ABL and of experimental vitamin E deficiency. Stabilization or improvement in electrophysiologic findings occurred with vitamin E supplementation. Neurophysiologic tests document retinal, central somatosensory and peripheral nerve lesions in vitamin E deficiency and provide an objective indication of response to treatment.

Peripheral neuropathy in abetalipoproteinemia

We studied the peripheral neuropathy of three sisters with abetalipoproteinemia. Clinically, a sensory neuropathy progressively increased in severity. There was a diminution in the amplitude of sensory action potentials and a slight-to-moderate slowing in maximum sensory conduction velocity, initially most marked in distal portions of the nerves. Motor conduction was normal, although EMG indicated subclinical signs of partial chronic denervation. The sural nerves showed a decreased number of large fibers (greater than 7 micron); in the patient with the neuropathy of shortest duration, small fibers and clusters of regenerating fibers indicated regeneration. In the two patients with advanced neuropathy, one-half the segments of teased fibers showed paranodal demyelination. Also, unmyelinated fibers showed evidence of regeneration.

Somatosensory evoked potentials in abetalipoproteinemia

Visual, brain-stem auditory, and somatosensory evoked potentials (SEPs) were obtained on a patient with known abetalipoproteinemia. Only the SEP was abnormal, and it correlated with the reported neuropathology of this disease. Serial SEP studies remained stable, as had the clinical condition of this patient on vitamin E therapy. The SEP may supplement clinical examination in follow-up of patients under treatment.

Electrophysiological studies in five cases of abetalipoproteinemia

Auditory brainstem responses (ABRs), visual and somatosensory evoked responses (VEPs and SEPs) and nerve conduction studies were conducted in 5 patients with abetalipoproteinemia. The ABRs were normal in all cases. The VEPs were of normal amplitude but of increased latencies in two patients. The four eldest patients had delayed cortical SEPs but normal peripheral sensory nerve conduction studies. The peripheral motor conduction velocities were normal in all cases. The peripheral sensory studies showed normal velocity when a response was seen; however, the amplitude of the response was often reduced or it was absent. The electrophysiological studies reported here support a model of axonal loss of large myelinated fibres with secondary demyelination in abetalipoproteinemia.

Combined vitamin A and E therapy prevents retinal electrophysiological deterioration in abetalipoproteinaemia

Eight patients with abetalipoproteinaemia had the typical ocular, systemic, and laboratory findings of this disease. Combined therapy with vitamins A and E was administered, starting as early as the first day of life and as late as 26 years of age. The patients were followed up for 2-6 years. Electroretinography was undertaken in all cases and electrooculography in some. After initiation of vitamin A and E therapy no progression of disturbed visual function could be detected in any patient. These objective tests of retinal function demonstrated that the combined vitamin A and E therapy may be useful in arresting retinal deterioration in abetalipoproteinaemia.

Acanthocytosis--biochemical and physiological considerations

Acanthocytosis represents an unusually pathological variant of red cell morphology which is encountered in a diverse group of inherited and acquired disease states. While the morphological features are similar in all instances, the biochemical lesions frequently differ. Most demonstrable abnormalities involve lipids although those acanthocytes associated with the McLeod phenotype are probably due to an alteration in a membrane protein. Acanthocytes, regardless of their etiology, usually have a decreased survival in the circulation owing to splenic sequestration and destruction.