Vitamin B12 and pernicious anemia--the dawn of molecular medicine

Mitigating pathogenesis for target discovery and disease subtyping

Treatments ideally mitigate pathogenesis, or the detrimental effects of the root causes of disease. However, existing definitions of treatment effect fail to account for pathogenic mechanism. We therefore introduce the Treated Root causal Effects (TRE) metric which measures the ability of a treatment to modify root causal effects. We leverage TREs to automatically identify treatment targets and cluster patients who respond similarly to treatment. The proposed algorithm learns a partially linear causal model to extract the root causal effects of each variable and then estimates TREs for target discovery and downstream subtyping. We maintain interpretability even without assuming an invertible structural equation model. Experiments across a range of datasets corroborate the generality of the proposed approach.

B12 deficiency-related glossitis is highly associated with high gastrin-17 and low pepsinogen I

BACKGROUND

The causes of vitamin B12 (B12) deficiency are varied and mainly related to gastric disorders. Glossitis is a common oral manifestation of B12 deficiency and is often first seen by dentists. This study aimed to investigate the correlation between B12 deficiency-related glossitis (B12-def glossitis) and gastric serum biomarkers [gastrin-17(G17), pepsinogen I (PGI), pepsinogen II (PGII), and anti-Helicobacter pylori (H. pylori) antibodies], and preliminarily discuss the etiology of B12-def glossitis.

METHODS

A cross-sectional study was conducted in patients complaining of glossodynia, burning sensation, or severe recurrent oral ulcers, but patients with a history of gastrectomy were excluded. All subjects underwent a uniform oral examination and hematological tests.

RESULTS

Of 243 patients, 133 with B12-def glossitis were in the case group, and 110 with other oral mucosal diseases (non-glossitis) and normal B12 levels were in the control group. In the case group, 84.2% (112/133) showed high G17 and low PGI levels (G17hi PGIlow ). Univariate logistic regression showed that G17hi PGIlow was a high-risk factor for B12-def glossitis (OR: 92.44; 95% CI: 35.91, 238.02). Subgroup analyses in the case group showed that the G17hi PGIlow group presented with lower B12 levels and a lower positive rate of anti-H. pylori antibodies compared to the non-G17hi PGIlow group.

CONCLUSION

Gastric serum biomarkers in patients with B12-def glossitis generally showed G17hi PGIlow , suggesting possible atrophy of gastric corpus and fundus mucosa. The G17hi PGIlow and non-G17hi PGIlow groups may represent different etiologies of B12 deficiency.

Nutritional Neuropathies

OBJECTIVE

This article reviews the etiologies, presentations, and management of neuropathies related to nutritional deficiencies.

LATEST DEVELOPMENTS

Peripheral neuropathy can be the predominant or only manifestation of certain nutrient deficiencies. Cognitive difficulties or involvement of other parts of the central nervous system, such as the optic nerve and spinal cord, may accompany nutritional peripheral neuropathies. In most patients, the nutritional deficiency may have a single predominant cause, but in some cases, multiple causes may coexist. Obesity, for unclear reasons, can be associated with nutrient deficiencies. The rising rates of bariatric surgery and the incidence of nutrient deficiencies following bariatric surgery make this a particularly relevant topic for neurologists.

ESSENTIAL POINTS

Neuropathies caused by nutrient deficiencies are preventable with appropriate supplementation in high-risk situations. Early recognition and prompt treatment are essential to ensure an optimal outcome and minimize neurologic morbidity.

Pernicious Anemia: The Hematological Presentation of a Multifaceted Disorder Caused by Cobalamin Deficiency

Pernicious anemia is still a neglected disorder in many medical contexts and is underdiagnosed in many patients. Pernicious anemia is linked to but different from autoimmune gastritis. Pernicious anemia occurs in a later stage of autoimmune atrophic gastritis when gastric intrinsic factor deficiency and consequent vitamin B₁₂ deficiency may occur. The multifaceted nature of pernicious anemia is related to the important role of cobalamin, which, when deficient, may lead to several dysfunctions, and thus, the proteiform clinical presentations of pernicious anemia. Indeed, pernicious anemia may lead to potentially serious long-term complications related to micronutrient deficiencies and their consequences and the development of gastric cancer and type 1 gastric neuroendocrine tumors. When not recognized in a timely manner or when pernicious anemia is diagnosed with delay, these complications may be potentially life-threatening and sometimes irreversible. The current review aimed to focus on epidemiology, pathogenesis, and clinical presentations of pernicious anemia in an attempt to look beyond borders of medical specialties. It aimed to focus on micronutrient deficiencies besides the well-known vitamin B₁₂ deficiency, the diagnostic approach for pernicious anemia, its long-term complications and optimal clinical management, and endoscopic surveillance of patients with pernicious anemia.

Cobamide remodeling

Cobamides are a family of structurally-diverse cofactors which includes vitamin B₁₂ and over a dozen natural analogs. Within the nucleotide loop structure, cobamide analogs have variable lower ligands that fall into three categories: benzimidazoles, purines, and phenols. The range of cobamide analogs that can be utilized by an organism is dependent on the specificity of its cobamide-dependent enzymes, and most bacteria are able to utilize multiple analogs but not all. Some bacteria have pathways for cobamide remodeling, a process in which imported cobamides are converted into compatible analogs. Here we discuss cobamide analog diversity and three pathways for cobamide remodeling, mediated by amidohydrolase CbiZ, phosphodiesterase CbiR, and some homologs of cobamide synthase CobS. Remodeling proteins exhibit varying degrees of specificity for cobamide substrates, reflecting different strategies to ensure that imported cobamides can be utilized.

Adult-onset CblC deficiency: a challenging diagnosis involving different adult clinical specialists

Background

Methylmalonic aciduria and homocystinuria, CblC type (OMIM #277400) is the most common disorder of cobalamin intracellular metabolism, an autosomal recessive disease, whose biochemical hallmarks are hyperhomocysteinemia, methylmalonic aciduria and low plasma methionine. Despite being a well-recognized disease for pediatricians, there is scarce awareness of its adult presentation. A thorough analysis and discussion of cobalamin C defect presentation in adult patients has never been extensively performed. This article reviews the published data and adds a new case of the latest onset of symptoms ever described for the disease.

Results

We present the emblematic case of a 45-year-old male, describing the diagnostic odyssey he ventured through to get to the appropriate treatment and molecular diagnosis. Furthermore, available clinical, biochemical and molecular data from 22 reports on cases and case series were collected, resulting in 45 adult-onset CblC cases, including our own. We describe the onset of the disease in adulthood, encompassing neurological, psychiatric, renal, ophthalmic and thromboembolic symptoms. In all cases treatment with intramuscular hydroxycobalamin was effective in reversing symptoms. From a molecular point of view adult patients are usually compound heterozygous carriers of a truncating and a non-truncating variant in the MMACHC gene.

Conclusion

Adult onset CblC disease is a rare disorder whose diagnosis can be delayed due to poor awareness regarding its presenting insidious symptoms and biochemical hallmarks. To avoid misdiagnosis, we suggest that adult onset CblC deficiency is acknowledged as a separate entity from pediatric late onset cases, and that the disease is considered in the differential diagnosis in adult patients with atypical hemolytic uremic syndromes and/or slow unexplained decline in renal function and/or idiopathic neuropathies, spinal cord degenerations, ataxias and/or recurrent thrombosis and/or visual field defects, maculopathy and optic disc atrophy. Plasma homocysteine measurement should be the first line for differential diagnosis when the disease is suspected. To further aid diagnosis, it is important that genes belonging to the intracellular cobalamin pathway are included within gene panels routinely tested for atypical hemolytic uremic syndrome and chronic kidney disorders.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13023-022-02179-y.

Some Morphology Frontiers of Dysplasia in the Tubular Gastrointestinal Tract: The Rodger C. Haggitt Memorial Lecture

This review, based on the content of the 2020 US Gastrointestinal Pathology Society's Rodger Haggitt Lecture, concerns an array of tubular gastrointestinal tract dysplastic or possible "predysplastic lesions" with an almost purely morphologic focus based on our collaborative efforts over the past few years. These processes include esophageal epidermoid metaplasia, Barrett esophagus-associated dysplasia, polypoid gastric dysplastic lesions, small intestinal dysplasia, and the ability of metastases to mimic it, the controversial "serrated epithelial change" encountered in the setting of long-standing ulcerative and Crohn colitis, and recently described anal columnar human papilloma virus-associated neoplasms.

Pernicious anemia: Pathophysiology and diagnostic difficulties

Pernicious anemia (PA) is the most common cause of vitamin B12 (cobalamin) deficiency anemia in the world. It is an autoimmune disease, comprising of salient features of autoimmune chronic atrophic gastritis (CAG) and cobalamin deficiency (CD). Although the anemia was first described as pernicious, it may well be controlled with vitamin B12 replacement. The onset and progression of PA is often insidious. Alternatively, patients may have no anemic symptoms since they become acclimatized to the subtle nature of the disease. Oftentimes, there is a possibility that the underlying disease may be missed unless a full blood count (FBC) is investigated, leading to hindrance in the treatment journey. Diagnostic challenges remain tangible for many practicing clinicians, since there is lack of reliable cobalamin assays to diagnose CD as well as clinical mimics, which simulate many other hematological conditions, such as myelodysplastic syndrome, acute leukemia, sideroblastic anemias, bone marrow failure states, thrombotic microangiopathy, and thromboembolism. Moreover, prompt recognition of the symptoms of CD is also vital, because some neurologic sequalae may become irreversible despite replenishing cobalamin. Herein, we discuss a literature review on the pathophysiology, challenging clinical presentations and diagnostic difficulties of PA. Since the cobalamin replacement therapy for PA is straightforward, it will not be discussed in this review.

Familial Risks between Pernicious Anemia and Other Autoimmune Diseases in the Population of Sweden

BACKGROUND

Pernicious anemia (PA) is an autoimmune disease (AID) which is caused by lack of vitamin B12 (cobalamin) due to its impaired uptake. PA is a multifactorial disease which is associated with a number of other AID comorbidities and which is manifested as part of autoimmune polyglandular syndrome. Due to the shortage of family studies on PA, we planned to address the problem by assessing familial risks for concordant PA between family members and for discordant PA in families of other AID patients.

METHODS

We collected data on patients diagnosed with AIDs from the Swedish hospitals and family data from a population register. We calculated standardized incidence ratios (SIRs) in families for concordant and discordant risks.

RESULTS

The number of PA patients in the offspring generation (for which the familial risk was calculated) was 7701; 278 (3.6%) patients had a family history of PA. The population prevalence of PA was 0.9/1000. The familial risk for PA was 3.88 when any first-degree relative was the proband, equal for men and women. The familial risk was two times higher between siblings than between offspring and parents which may be due to complex genetic background. Associations of PA with 14 discordant AIDs were significant; these included some AIDs that have previously been described as comorbidities in PA patients and several yet unreported associations, including rheumatoid arthritis and other AIDs.

CONCLUSIONS

The familial risks for PA were high suggesting multifactorial genetic etiology. The results call for further population-level studies to unravel mechanisms of familial PA which may help to understand the etiology of this disease.

Intrinsic factor recognition promotes T helper 17/T helper 1 autoimmune gastric inflammation in patients with pernicious anemia

The intrinsic factor is the major humoral autoantigen in pernicious anemia/autoimmune gastritis. Although many studies have examined the autoantibody response to intrinsic factor and H⁺,K⁺-ATPase, no information is available on possible pathogenic mechanisms mediated by intrinsic factor - specific gastric T cells. Aim of this study was to investigate intrinsic factor-specific T cells in the gastric mucosa of pernicious anemia patients and define their functional properties. For the first time we provide evidence that gastric mucosa of pernicious anemia patients harbour a high proportion (20%) of autoreactive activated CD4⁺ T-cell clones that specifically recognize intrinsic factor. Most of these clones (94%) showed a T helper 17 or T helper 1 profile. All intrinsic factor-specific clones produced tumor necrosis factor-α, interleukin-21 and provided substantial help for B-cell immunoglobulin production. Most mucosa-derived intrinsic factor-specific T-cell clones expressed cytotoxicity against target cells. Our results indicate that activation of intrinsic factor-specific T helper 17 and T helper 1 T cells in the gastric mucosa represent a key effector mechanism in pernicious anemia suggesting that the T helper 17/T helper 1 pathway may represent a novel target for the prevention and treatment of the disease.

Inherited selective cobalamin malabsorption in Komondor dogs associated with a CUBN splice site variant

BACKGROUND

Three Komondor dogs in a small family and 3 sporadic cases exhibited a constellation of signs that included juvenile-onset of failure-to-thrive, inappetence, vomiting and/or diarrhea, and weakness. In each we documented dyshematopoiesis, increased anion gap, methylmalonic acidemia/-uria, and serum cobalamin deficiency. Urine protein electrophoresis demonstrated excretion of cubam ligands. All clinical signs and metabolic abnormalities, except proteinuria, were reversed by regular parenteral cobalamin administration. The pattern of occurrence and findings in the disorder suggested an autosomal recessive inheritance of cobalamin malabsorption with proteinuria, a condition in humans called Imerslund-Gräsbeck syndrome. The purpose of this study was to determine the molecular cause of this disorder in Komondors.

RESULTS

Whole genome sequencing of two affected Komondor dogs of unknown relatedness and one parent and a clinically-normal littermate of an affected dog revealed a pathogenic single-base change in the CUBN intron 55 splice donor consensus sequence (NM_001003148.1: c.8746 + 1G > A) that was homozygous in affected dogs and heterozygous in the unaffected parents. Alleles of the variant co-segregated with alleles of the disease locus in the entire family and all more distantly-related sporadic cases. A population study using a simple allele-specific DNA test indicated mutant allele frequencies of 8.3 and 4.5% among North American and Hungarian Komondors, respectively.

CONCLUSIONS

DNA testing can be used diagnostically in Komondors when clinical signs are suggestive of cobalamin deficiency or to inform Komondor breeders prospectively and prevent occurrence of future affected dogs. This represents the third cubilin variant causing inherited selective cobalamin malabsorption in a large animal ortholog of human Imerslund-Gräsbeck syndrome.

Gastrointestinal Handling of Water-Soluble Vitamins

Nine compounds are classified as water-soluble vitamins, eight B vitamins and one vitamin C. The vitamins are mandatory for the function of numerous enzymes and lack of one or more of the vitamins may lead to severe medical conditions. All the vitamins are supplied by food in microgram to milligram quantities and in addition some of the vitamins are synthesized by the intestinal microbiota. In the gastrointestinal tract, the vitamins are liberated from binding proteins and for some of the vitamins modified prior to absorption. Due to their solubility in water, they all require specific carriers to be absorbed. Our current knowledge concerning each of the vitamins differs in depth and focus and is influenced by the prevalence of conditions and diseases related to lack of the individual vitamin. Because of that we have chosen to cover slightly different aspects for the individual vitamins. For each of the vitamins, we summarize the physiological role, the steps involved in the absorption, and the factors influencing the absorption. In addition, for some of the vitamins, the molecular base for absorption is described in details, while for others new aspects of relevance for human deficiency are included. © 2018 American Physiological Society. Compr Physiol 8:1291-1311, 2018.

Alfred Nobel and His Prizes: From Dynamite to DNA

Alfred Nobel was one of the most successful chemists, inventors, entrepreneurs, and businessmen of the late nineteenth century. In a decision later in life, he rewrote his will to leave virtually all his fortune to establish prizes for persons of any nationality who made the most compelling achievement for the benefit of mankind in the fields of chemistry, physics, physiology or medicine, literature, and peace among nations. The prizes were first awarded in 1901, five years after his death. In considering his choice of prizes, it may be pertinent that he used the principles of chemistry and physics in his inventions and he had a lifelong devotion to science, he suffered and died from severe coronary and cerebral atherosclerosis, and he was a bibliophile, an author, and mingled with the literati of Paris. His interest in harmony among nations may have derived from the effects of the applications of his inventions in warfare ("merchant of death") and his friendship with a leader in the movement to bring peace to nations of Europe. After some controversy, including Nobel's citizenship, the mechanisms to choose the laureates and make four of the awards were developed by a foundation established in Stockholm; the choice of the laureate for promoting harmony among nations was assigned to the Norwegian Storting, another controversy. The Nobel Prizes after 115 years remain the most prestigious of awards. This review describes the man, his foundation, and the prizes with a special commentary on the Nobel Prize in Physiology or Medicine.

The Lived Experience of Anemia Without a Cause

This article explores anemia without an obvious cause from two perspectives: a patient and the evidence. Although evidence is required to drive favorable patient outcomes, the focus on evidence often hides the patient experience during diagnosis and treatment. Knowledge of experience with evidence can provide a deeper perspective for clinical decision making and meet nursing's ethical mandate to relieve suffering. Although one patient experience does not reflect every patient experience, this patient's experience demonstrates how difficult and dark anemia can be.

Mechanisms of Autoantibody-Induced Pathology

Autoantibodies are frequently observed in healthy individuals. In a minority of these individuals, they lead to manifestation of autoimmune diseases, such as rheumatoid arthritis or Graves' disease. Overall, more than 2.5% of the population is affected by autoantibody-driven autoimmune disease. Pathways leading to autoantibody-induced pathology greatly differ among different diseases, and autoantibodies directed against the same antigen, depending on the targeted epitope, can have diverse effects. To foster knowledge in autoantibody-induced pathology and to encourage development of urgently needed novel therapeutic strategies, we here categorized autoantibodies according to their effects. According to our algorithm, autoantibodies can be classified into the following categories: (1) mimic receptor stimulation, (2) blocking of neural transmission, (3) induction of altered signaling, triggering uncontrolled (4) microthrombosis, (5) cell lysis, (6) neutrophil activation, and (7) induction of inflammation. These mechanisms in relation to disease, as well as principles of autoantibody generation and detection, are reviewed herein.

Megaloblastic Anemias: Nutritional and Other Causes

Vitamin B₁₂ and folate deficiencies are major causes of megaloblastic anemia. Causes of B₁₂ deficiency include pernicious anemia, gastric surgery, intestinal disorders, dietary deficiency, and inherited disorders of B₁₂ transport or absorption. The prevalence of folate deficiency has decreased because of folate fortification, but deficiency still occurs from malabsorption and increased demand. Other causes include drugs and inborn metabolic errors. Clinical features of megaloblastic anemia include anemia, cytopenias, jaundice, and megaloblastic marrow morphology. Neurologic symptoms occur in B₁₂ deficiency, but not in folate deficiency. Management includes identifying any deficiency, establishing its cause, and replenishing B₁₂ or folate parenterally or orally.

A case of asymptomatic pancytopenia with clinical features of hemolysis as a presentation of pernicious anemia

Pernicious anemia is an autoimmune disease with a variety of clinical presentations. We describe a case of pernicious anemia presenting with pancytopenia with hemolytic features. Further workup revealed very low vitamin B12 levels and elevated methylmalonic acid. It is important for a general internist to identify pernicious anemia as one of the cause of pancytopenia and hemolytic anemia to avoid extensive workup. Pernicious anemia can present strictly with hematological abnormalities without neurological problems or vice versa as in our case.

Autoimmune Metaplastic Atrophic Gastritis: Recognizing Precursor Lesions for Appropriate Patient Evaluation

Autoimmune metaplastic atrophic gastritis (AMAG) is a significant risk factor for pernicious anemia and gastric neoplasia. Still, the histologic features of AMAG are frequently overlooked, especially in the early stages of the disease. The purpose of our study, therefore, was to catalogue the progression of histologic changes that precede the development of AMAG in affected individuals. Over a 2-year period (2012 to 2014), the diagnosis of AMAG was rendered on material from 113 patients seen at Johns Hopkins Hospital (∼1.8% of "in house" gastric biopsies). Prior gastric body biopsies had been performed on 54 (48%) patients in the cohort, and the majority of these specimens had also shown AMAG. Eighteen of the previous biopsies, however, carried a diagnosis other than AMAG: 13 inactive chronic gastritis, 2 acute Helicobacter pylori gastritis, and 1 each of eosinophilic gastritis, iron pill gastritis, and proton-pump inhibitor-like effect. Upon review of these 18 biopsies, the most common histologic findings were heavy full-thickness or deep lamina propria chronic inflammation (12), inflammatory destruction of oxyntic glands (12), metaplasia (intestinal, pyloric, or pancreatic acinar) (10), prominent lamina propria eosinophils (8), and parietal cell pseudohypertrophy (4). At least 2 of these features were present in the majority (13, 72%) of the biopsies. In addition, 7 (58%) of these patients were also found to have another autoimmune or inflammatory disorder before the diagnosis of AMAG. Although subtle, histologic features of developing AMAG are identifiable in routine gastric body biopsies. When metaplasia, full-thickness chronic inflammation, and/or oxyntic destruction are seen, a note suggesting laboratory testing and/or close clinical follow-up in this subset of patients may be warranted.

Association of acquired thrombotic thrombocytopaenic purpura in a patient with pernicious anaemia

Pernicious anaemia is an autoimmune disease caused by intrinsic factor antibody; it leads to vitamin B12 deficiency and is marked by ineffective erythropoiesis. Haematological features reveal macrocytosis, hyperchromasia and hypersegmented neutrophils. Schistocytes are typically seen in microangiopathy, such as in thrombotic thrombocytopaenic purpura (TTP)/haemolytic uraemic syndrome or disseminated intravascular haemolysis (DIC). We report a case of a patient with severe anaemia who presented to the emergency room. Peripheral smear revealed macrocytosis, hypersegmented neutrophils and marked schistocytosis. The patient also had high reticulocyte count with high serum lactate dehydrogenase, elevated D-dimer, low fibrinogen and low haptoglobin. Vitamin B12 level came back low and the presence of intrinsic factor antibody confirmed pernicious anaemia. ADAMTS13 level was noted to be mildly reduced, which raised the suspicion of the association of acquired TTP with pernicious anaemia. Acquired TTP is another autoimmune disorder and its association with pernicious anaemia needs further evaluation.

Pernicious anemia. From past to present

Pernicious anemia is currently the most common cause of vitamin B12 deficiency in Western countries. The histological lesion upon which this condition is based is autoimmune chronic atrophic gastritis. The destruction of parietal cells causes a deficiency in intrinsic factor, an essential protein for vitamin B12 absorption in the terminal ileum. Advances in the last two decades have reopened the debate on a disease that seemed to have been forgotten due to its apparent simplicity. The new role of H. pylori, the value of parietal cell antibodies and intrinsic factor antibodies, the true usefulness of serum vitamin B12 levels, the risk of adenocarcinoma and gastric carcinoids and oral vitamin B12 treatment are just some of the current issues analyzed in depth in this review.