On having no beta-lipoprotein. A syndrome comprising a-beta-lipoproteinaemia, acanthocytosis, and steatorrhoea

Syndromic Retinitis Pigmentosa: A Narrative Review

Retinitis pigmentosa (RP) encompasses inherited retinal dystrophies, appearing either as an isolated eye condition or as part of a broader systemic syndrome, known as syndromic RP. In these cases, RP includes systemic symptoms impacting other organs, complicating diagnosis and management. This review highlights key systemic syndromes linked with RP, such as Usher, Bardet-Biedl, and Alström syndromes, focusing on genetic mutations, inheritance, and clinical symptoms. These insights support clinicians in recognizing syndromic RP early. Ocular signs like nystagmus and congenital cataracts may indicate systemic disease, prompting genetic testing. Conversely, systemic symptoms may necessitate eye exams, even if vision symptoms are absent. Understanding the systemic aspects of these syndromes emphasizes the need for multidisciplinary collaboration among ophthalmologists, pediatricians, and other specialists to optimize patient care. The review also addresses emerging genetic therapies aimed at both visual and systemic symptoms, though more extensive studies are required to confirm their effectiveness. Overall, by detailing the genetic and clinical profiles of syndromic RP, this review seeks to aid healthcare professionals in diagnosing and managing these complex conditions more effectively, enhancing patient outcomes through timely, specialized intervention.

Deep brain stimulation in Bassen-Kornzweig syndrome: Still effective after 22 years

Introduction

Bassen-Kornzweig syndrome or abetalipoproteinemia is a rare autosomal recessive disorder characterized by a malabsorption of dietary fat and fat-soluble vitamins. This deficiency can lead to a variety of symptoms, including hematological (acanthocytosis, bleeding tendency), neurological (tremor, spinocerebellar ataxia), neuromuscular (myopathy), ophthalmological symptoms (retinitis pigmentosa). The thalamic ventral intermediate nucleus (VIM) is a well-established target for deep brain stimulation (DBS) in the treatment of refractory tremor.

Research question

We evaluated the clinical long-term follow-up (22 years) after VIM-DBS for refractory tremor in abetalipoproteinemia. We also evaluated the adjustments of stimulation settings and medication balance after DBS procedure.

Material and methods

We report a 53-year-old male who suffers from abetalipoproteinemia since the age of 17. He underwent bilateral VIM-DBS to treat his disabling refractory intentional tremor at the age of 31. He still has a very good response to his tremor with limited stimulation adaptations over 22 years. For more than two decades follow-up, the treatment significantly improved his ADL functions and therefore also the QoL.

Discussion and conclusion

The VIM target for DBS in the treatment of refractory tremor has been extensively reported in the literature. Thalamic VIM-DBS is a safe and effective treatment for a severe, refractory tremor as a neurological symptom caused by abetalipoproteinemia. It also highlights the importance of a multidisciplinary follow-up, to adjust and optimize the stimulation/medication balance after VIM-DBS surgery.

Imaging Erythrocyte Sedimentation in Whole Blood

The erythrocyte sedimentation rate (ESR) is one of the oldest medical diagnostic tools. However, currently there is some debate on the structure formed by the cells during the sedimentation process. While the conventional view is that erythrocytes sediment as separate aggregates, others have suggested that they form a percolating gel, similar to other colloidal suspensions. However, visualization of aggregated erythrocytes, which would settle the question, has always been challenging. Direct methods usually study erythrocytes in 2D situations or low hematocrit (∼1%). Indirect methods, such as scattering or electric measurements, provide insight on the suspension evolution, but cannot directly discriminate between open or percolating structures. Here, we achieved a direct probing of the structures formed by erythrocytes in blood at stasis. We focused on blood samples at rest with controlled hematocrit of 45%, from healthy donors, and report observations from three different optical imaging techniques: direct light transmission through thin samples, two-photon microscopy and light-sheet microscopy. The three techniques, used in geometries with thickness from 150 μm to 3 mm, highlight that erythrocytes form a continuous network with characteristic cracks, i.e., a colloidal gel. The characteristic distance between the main cracks is of the order of ∼100 μm. A complete description of the structure then requires a field of view of the order of ∼1 mm, in order to obtain a statistically relevant number of structural elements. A quantitative analysis of the erythrocyte related processes and interactions during the sedimentation need a further refinement of the experimental set-ups.

Acanthocyte Sedimentation Rate as a Diagnostic Biomarker for Neuroacanthocytosis Syndromes: Experimental Evidence and Physical Justification

(1) Background: Chorea-acanthocytosis and McLeod syndrome are the core diseases among the group of rare neurodegenerative disorders called neuroacanthocytosis syndromes (NASs). NAS patients have a variable number of irregularly spiky erythrocytes, so-called acanthocytes. Their detection is a crucial but error-prone parameter in the diagnosis of NASs, often leading to misdiagnoses. (2) Methods: We measured the standard Westergren erythrocyte sedimentation rate (ESR) of various blood samples from NAS patients and healthy controls. Furthermore, we manipulated the ESR by swapping the erythrocytes and plasma of different individuals, as well as replacing plasma with dextran. These measurements were complemented by clinical laboratory data and single-cell adhesion force measurements. Additionally, we followed theoretical modeling approaches. (3) Results: We show that the acanthocyte sedimentation rate (ASR) with a two-hour read-out is significantly prolonged in chorea-acanthocytosis and McLeod syndrome without overlap compared to the ESR of the controls. Mechanistically, through modern colloidal physics, we show that acanthocyte aggregation and plasma fibrinogen levels slow down the sedimentation. Moreover, the inverse of ASR correlates with the number of acanthocytes (R2=0.61, p=0.004). (4) Conclusions: The ASR/ESR is a clear, robust and easily obtainable diagnostic marker. Independently of NASs, we also regard this study as a hallmark of the physical view of erythrocyte sedimentation by describing anticoagulated blood in stasis as a percolating gel, allowing the application of colloidal physics theory.

An in silico model of retinal cholesterol dynamics (RCD model): insights into the pathophysiology of dry AMD

We developed an in silico mathematical model of retinal cholesterol (Ch) dynamics (RCD) to quantify the physiological rate of Ch turnover in the rod outer segment (ROS), the lipoprotein transport mechanisms by which Ch enters and leaves the outer retina, and the rates of drusen growth and macrophage-mediated clearance in dry age-related macular degeneration. Based on existing experimental data and mechanistic hypotheses, we estimated the Ch turnover rate in the ROS to be 1–6 pg/mm²/min, dependent on the rate of Ch recycling in the outer retina, and found comparable rates for LDL receptor-mediated endocytosis of Ch by the retinal pigment epithelium (RPE), ABCA1-mediated Ch transport from the RPE to the outer retina, ABCA1-mediated Ch efflux from the RPE to the choroid, and the secretion of 70 nm ApoB-Ch particles from the RPE. The drusen growth rate is predicted to increase from 0.7 to 4.2 μm/year in proportion to the flux of ApoB-Ch particles. The rapid regression of drusen may be explained by macrophage-mediated clearance if the macrophage density reaches ∼3,500 cells/mm². The RCD model quantifies retinal Ch dynamics and suggests that retinal Ch turnover and recycling, ApoB-Ch particle efflux, and macrophage-mediated clearance may explain the dynamics of drusen growth and regression.

The early years of lipoprotein research: from discovery to clinical application

This review outlines major milestones in the first four decades of lipoprotein research beginning with their discovery nearly 90 years ago. It focuses on the contributions of some of the key investigators during this era, and findings that set the stage for widespread clinical implementation of lipoprotein testing for evaluation and management of CVD risk.

Homozygous MTTP and APOB mutations may lead to hepatic steatosis and fibrosis despite metabolic differences in congenital hypocholesterolemia

BACKGROUND & AIMS

Non-alcoholic steatohepatitis leading to fibrosis occurs in patients with abetalipoproteinemia (ABL) and homozygous or compound heterozygous familial hypobetalipoproteinemia (Ho-FHBL). We wanted to establish if liver alterations were more frequent in one of both diseases and were influenced by comorbidities.

METHODS

We report genetic, clinical, histological and biological characteristics of new cases of ABL (n =7) and Ho-FHBL (n = 7), and compare them with all published ABL (51) and Ho-FHBL (22) probands.

RESULTS

ABL patients, diagnosed during infancy, presented mainly with diarrhea, neurological and ophthalmological impairments and remained lean, whereas Ho-FHBL were diagnosed later, with milder symptoms often becoming overweight in adulthood. Despite subtle differences in lipid phenotype, liver steatosis was observed in both groups with a high prevalence of severe fibrosis (5/27 for Ho-FHBL vs. 4/58 for ABL (n.s.)). Serum triglycerides concentration was higher in Ho-FHBL whereas total and HDL-cholesterol were similar in both groups. In Ho-FHBL liver alterations were found to be independent from the apoB truncation size and apoB concentrations.

CONCLUSIONS

Our findings provide evidence for major liver abnormalities in both diseases. While ABL and Ho-FHBL patients have subtle differences in lipid phenotype, carriers of APOB mutations are more frequently obese. These results raise the question of a complex causal link between apoB metabolism and obesity. They suggest that the genetic defect in VLDL assembly is critical for the occurrence of liver steatosis leading to fibrosis and shows that obesity and insulin resistance might contribute by increasing lipogenesis.

Dégénérescence tapéto-rétinienne associée à un Syndrome hypolipidémique

1. A tapeto-retinal degeneration can be observed in association with a disturbance in the metabolism of the lipids.

2. This fact gives a new argument in favor of the hypothesis that the tapeto-retinal degeneration is due to a metabolic alteration and more probably to an enzymatic disturbance in the sensorial epithelium of the retina.

3. The investigations of Hooft et al (1962) demonstrate that it may be an insufficiency of the pyridine nucleotide coenzymes following a primary disturbance in the metabolism of tryptophane.

4. In a case of pigmentary retinopathy, it is now indispensable to do a systematic blood examination both on the morphological and on the biochemical and metabolic point of view.

Tapetoretinal Degenerations and Disorders of lipid Metabolism. Part I: Clinical, Genetic, Pathological, and Therapeutic Aspects

The clinical findings in a group of syndromes in which tapetoretinal degenerations are associated with systemic lipid disorders are described. This group includes abetalipoproteinemia (the syndrome of Bassen and Kornzweig), Refsum's syndrome, Neuronal Ceroid Lipofuscinosis, and Cockayne's syndrome. AII four are transmitted by single autosomal recessive genes. The pathological findings are discussed. If diagnosed early enough, abetalipoproteinemia should be treated by administration of vitamin A, and Refsum's syndrome by restriction of intake of phytanic acid and phytol.

Tapetoretinal Degenerations and Disorders of Lipid Metabolism. Part II: Biochemical Aspects

Inherited tapetoretinal degenerations associated with, or caused by, abnormalities in lipid metabolism are discussed in terms of recent findings regarding their etiology. The biochemical basis of these tapetoretinal degenerations may be summarized as follows.

(a) In abetalipoproteinemia (the Bassen-Kornzweig syndrome) there is a complete absence of all plasma lipoproteins except HDL (alfalipoprotein; high density lipoprotein). In addition the levels of plasma lipids, including vitamin A, are grossly dimished. The genetically-caused basic defect in this disorder is the absence of a specific protein component, apoLP-ser, in the plasma lipoproteins.

(b) In a milder form of hypobetalipoproteinemia, transmitted as an autosomal dominant trait, there is little, if any, retinal degeneration.

(c) Refsum's syndrome is characterized by greatly increased plasma levels of phytanic acid, a 20-carbon branched-chain fatty acid. This substance is not synthesized in the body, but originates from dietary sources only. Patients with Refsum's syndrome lack the enzyme (phytanic acid oxidase) necessary to oxidize this fatty acid, and its accumulation in the tissues has severe consequences. Therapeutic measures, consisting of restriction of dietary phytanic acid, have given encouraging results.

(d) Three forms of Batten's disease (neuronal ceroid lipofuscinosis) are now recognized. These are (1) the rapidly progressive (Jansky-Bielschowsky) form, (2) the chronic (Batten-Mayou-Vogt-Spielmeyer-Sjögren) form, which is the most common, and (3) the late onset (Kufs') form. All are associated — to varying degrees — with an accumulation of autofluorescent ceroidlipofuscin pigments. The enzymatic defect is believed to consist of abnormalities in peroxidase enzymes.

(e) Other tapetoretinal degenerations thought to be associated with defects in lipid metabolism are discussed briefly. These include Hooffs disease, Cockayne's syndrome, and Alstrom's syndrome.

Deep brain stimulation for the treatment of tremor and ataxia associated with abetalipoproteinemia

BACKGROUND

Abetalipoproteinemia is a rare disorder of fat absorption, characterized by vitamin deficiency, acanthocytosis, and neurologic symptoms including ataxia and tremor.

CASE REPORT

A 41-year-old male with abetalipoproteinemia is presented. He underwent staged bilateral thalamic deep brain stimulation (DBS) for the treatment of his tremors. After DBS, the patient achieved significant improvements in his tremors, ataxia, and quality of life.

DISCUSSION

Thalamic DBS proved to be both safe and efficacious in the management of ataxia and tremors in a patient with abetalipoproteinemia. This is the first report of DBS in abetalipoproteinemia in the literature.

Disc swelling in abetalipoproteinemia: a novel feature of Bassen-Kornzweig syndrome

PURPOSE

Abetalipoproteinemia is a very rare disease with multisystemic manifestations.

METHODS

Retrospective, case report.

RESULTS

We report a 9-year-old girl with a history of Bassen-Kornzweig syndrome diagnosed at the age of 3. The patient was referred to us by the pediatricians for ocular assessment. During the examination, an atypical pigmentary retinopathy and bilateral swelling of the optic discs were observed, with no consequences to her visual acuity.

CONCLUSIONS

Ophthalmic manifestations in Bassen-Kornzweig syndrome are not uncommon. We describe, for the first time, bilateral swelling of the optic discs, a sign that appears directly associated with abetalipoproteinemia.

Chorea-acanthocytosis: A Mimicker of Huntington Disease Case Report and Review of the Literature

BACKGROUND

Neuroacanthocytosis consists of a group of rare heterogeneous neurodegenerative disorders associated with acanthocytosis. Chorea-acanthocytosis, a variety of neuroacanthocytosis, is an autosomal recessive condition with clinical and radiologic features similar to Huntington disease. Although difficult, distinguishing between these entities is crucial as the implications for genetic counseling are significant.

REVIEW SUMMARY

We report the case of a 33-year-old female who presented to our institution with a 3-year history of chorea. The patient's prominent orofacial symptoms and the presence of acanthocytes on peripheral blood smear led to the correct diagnosis of chorea-acanthocytosis.

CONCLUSIONS

The significant similarities between chorea-acanthocytosis and Huntington disease at the clinical and radiologic levels can lead to an initial misdiagnosis. Clinical clues suggestive of chorea-acanthocytosis include prominent orofacial dyskinesias, often causing dysarthria and dysphagia. Acanthocytosis, when present on peripheral blood smear, can confirm the diagnosis.

[Familial hypobetalipoproteinemia]

We present the case of a 5-month-old girl, with consanguineous parents, who was born at 28 weeks of gestation and who showed intermittent signs of abdominal distension accompanied by increased regurgitation and vomiting after food intake. Significant biochemical alterations (reduced levels of triglicerides, cholesterol, and vitamin A and absence of apolipoprotein B and vitamin E) led to the diagnosis of homozygous hypobetalipoproteinemia, which was subsequently confirmed by genetic studies.