Imerslund-Grasbeck syndrome in a Chinese family with distinct skin lesions refractory to vitamin B12

Imerslund-Gräsbeck syndrome: a comprehensive review of reported cases

Imerslund-Gräsbeck syndrome (IGS) is a rare autosomal recessive disorder characterized by vitamin B12 malabsorption. Most patients present with non-specific symptoms attributed to vitamin B12 deficiency, and proteinuria. Patients may if untreated, develop severe neurocognitive manifestations. If recognized and treated with sufficient doses of vitamin B12, patients recover completely. We provide, for the first time, an overview of all previously reported cases of IGS. In addition, we provide a complete review of IGS and describe two new patients.

Clinical and molecular characteristics of imerslund-gräsbeck syndrome: First report of a novel Frameshift variant in Exon 11 of AMN gene

INTRODUCTION

Imerslund-Gräsbeck syndrome (IGS) is a rare autosomal-recessive disorder characterized by selective vitamin B12 malabsorption, megaloblastic anemia, and proteinuria. The precise incidence of this disorder is unknown in the Middle East and Arab countries. The disease is caused by a homozygous variant in either AMN or CUBN genes. In addition, some compound heterozygous variants are reported.

METHODS

Clinical and laboratory data of patients diagnosed with IGS in Oman were retrospectively collected. Mutation analysis for all genes involved in vitamin B12/folic acid metabolism and megaloblastic anemia was conducted using next-generation sequencing (NGS).

RESULTS

Three siblings (2 girls and a boy) have been diagnosed with the condition. They exhibit a phenotypic variability with different age of presentation and different spectrum of disease. All patients harbor a novel biallelic frameshift mutation in exon 11 of AMN gene (p.Pro409Glyfs*), which was not reported previously in the literature. Both parents are heterozygotes for the same variant. All patients responded well to vitamin B12 parenteral therapy, but proteinuria persisted.

CONCLUSION

In communities with high incidence of consanguinity, cases of early-onset vitamin B12 deficiency should be thoroughly investigated to explore the possibility of Imerslund-Gräsbeck syndrome and other vitamin B12-related hereditary disorders. Further local and regional studies are highly recommended.

A curious case of Fever and hyperpigmentation

Megaloblastic anaemia as a cause of pyrexia is a rare entity. Similarly, hyperpigmentation of skin has rarely been reported as the presenting manifestation of folate and/or vitamin B12 deficiency. The author reports the case of a patient who presented with fever and hyperpigmentation and was diagnosed to have megaloblastic anaemia secondary to vitamin B12 and folate deficiency after other infective, inflammatory/autoimmune, endocrine causes of pyrexia and hyperpigmentation were excluded by appropriate investigations. The patient responded remarkably well to the treatment with vitamin B12 and folic acid supplementation. Although presentation of megaloblastic anaemia as isolated fever or hyperpigmentation are noted in literature, simultaneous fever and hyperpigmentation as its initial presentation is exceedingly rare.

Unusual cause of childhood anemia: Imerslund Grasbeck syndrome

Imerslund Grasbeck syndrome (IGS) is a rare autosomal recessive childhood disorder characterized by selective Vitamin (vit) B 12 malabsorption with asymptomatic proteinuria without any structural renal pathology. The patients stay healthy for decades with life-long parenteral vit B12. We report a case of young female who presented with pancytopenia and proteinuria, evaluated in local hospitals as chronic hemolytic anemia (autoimmune cause), finally diagnosed as IGS on complete evaluation. She was treated with injectable vit B12 (1000 μg cyanocobalalmin) and showed drastic recovery. IGS should be considered in patients with megaloblastic anemia not responding to oral vit B12 and associated proteinuria.

Exome sequencing reveals cubilin mutation as a single-gene cause of proteinuria

In two siblings of consanguineous parents with intermittent nephrotic-range proteinuria, we identified a homozygous deleterious frameshift mutation in the gene CUBN, which encodes cubulin, using exome capture and massively parallel re-sequencing. The mutation segregated with affected members of this family and was absent from 92 healthy individuals, thereby identifying a recessive mutation in CUBN as the single-gene cause of proteinuria in this sibship. Cubulin mutations cause a hereditary form of megaloblastic anemia secondary to vitamin B(12) deficiency, and proteinuria occurs in 50% of cases since cubilin is coreceptor for both the intestinal vitamin B(12)-intrinsic factor complex and the tubular reabsorption of protein in the proximal tubule. In summary, we report successful use of exome capture and massively parallel re-sequencing to identify a rare, single-gene cause of nephropathy.

Cutaneous manifestations of nutritional deficiency

PURPOSE OF REVIEW

Nutritional deficiency, a global problem, remains uncommon in developed nations. Associated morbidity and mortality make it imperative that clinicians remain familiar with the clinical signs and symptoms of nutritional deficiencies to facilitate diagnosis. This article will review the cutaneous findings and recent literature regarding B12, niacin, zinc, vitamin A, kwashiorkor, biotin and selenium deficiencies, along with the clinical entities of noma and phrynoderma.

RECENT FINDINGS

Much of our understanding of the clinical manifestations of nutritional deficiencies comes from old literature; however, recent case reports and series have highlighted several patient populations that may be at risk from acquired deficiencies, including patients with anorexia nervosa, cystic fibrosis, patients receiving long-term tube-feeding and those with perceived or real food allergy. There can be significant clinical overlap between various micronutrient, protein and vitamin deficiencies. Additionally, providers should consider the possibility of multiple deficiencies coexisting in individual patients.

SUMMARY

Reports of nutritional deficiency continue to surface in developed nations and pediatricians need to have a basic understanding of their clinical manifestations. The skin is commonly affected and can be the presenting sign of illness. A higher clinical suspicion needs to be maintained in certain populations.

Genetically heterogeneous selective intestinal malabsorption of vitamin B12: founder effects, consanguinity, and high clinical awareness explain aggregations in Scandinavia and the Middle East

Selective intestinal malabsorption of vitamin B(12) causing juvenile megaloblastic anemia (MGA; MIM# 261100) is a recessively inherited disorder that is believed to be rare except for notable clusters of cases in Finland, Norway, and the Eastern Mediterranean region. The disease can be caused by mutations in either the cubilin (CUBN; MGA1; MIM# 602997) or the amnionless (AMN; MIM# 605799) gene. To explain the peculiar geographical distribution, we hypothesized that mutations in one of the genes would mainly be responsible for the disease in Scandinavia, and mutations in the other gene in the Mediterranean region. We studied 42 sibships and found all cases in Finland to be due to CUBN (three different mutations) and all cases in Norway to be due to AMN (two different mutations), while in Turkey, Israel, and Saudi Arabia, there were two different AMN mutations and three different CUBN mutations. Haplotype evidence excluded both CUBN and AMN conclusively in five families and tentatively in three families, suggesting the presence of at least one more gene locus that can cause MGA. We conclude that the Scandinavian cases are typical examples of enrichment by founder effects, while in the Mediterranean region high degrees of consanguinity expose rare mutations in both genes. We suggest that in both regions, physician awareness of this disease causes it to be more readily diagnosed than elsewhere; thus, it may well be more common worldwide than previously thought.

A urinary radioisotope-binding assay to diagnose Gräsbeck-Imerslund disease

BACKGROUND

Gräsbeck-Imerslund disease (congenital familial selective vitamin B12-malabsorption with proteinuria, MGA1, MIM No. 261100) is a rare disorder displaying autosomal recessive inheritance. This study was designed to investigate the usefulness of measuring the activity of the urinary receptor for the intrinsic factor-cobalamin complex as a tool to diagnose this disease.

METHODS

The receptor activity was measured by a radioisotope-binding assay, using phenyl-Sepharose gel as the adsorbant solid phase of the receptor.

RESULTS

In 10 Finnish patients, urinary receptor activity was on the average 640 times (15-1400 times) lower than that in 13 healthy control subjects: mean values of 0.1 nmol/mol (range, 0.01-0.32 nmol/mol) and 6.4 nmol/mol (range, 3.8-12.4 nmol/mol) creatinine, respectively. The mean value of urinary receptor activity in 11 first-degree, healthy relatives of the patients was 4.6 nmol/mol (range, 1.1-10.4 nmol/mol) creatinine, a difference from levels in control subjects that is not statistically significant. When the first-degree relatives were divided into heterozygotes (parents and siblings heterozygous for the haplotype of genetic markers associated with the disease gene) and wild-type homozygotes (siblings not displaying the disease haplotype), no difference was seen.

CONCLUSION

Determination of receptor activity in the urine is a highly accurate method for diagnosis of Gräsbeck-Imerslund disease at an early stage, but it does not detect carriers of the disorder.