The Role of Hematopoietic Cell Transplant in the Glycoprotein Diseases

Hematopoietic Stem Cell Transplantation for Storage Disorders: Present Status

Storage disorders are a group of inborn errors of metabolism caused by the defective activity of lysosomal enzymes or transporters. All of these disorders have multisystem involvement with variable degrees of neurological features. Neurological manifestations are one of the most difficult aspects of treatment concerning these diseases. The available treatment modalities for some of these disorders include enzyme replacement therapy, substrate reduction therapy, hematopoietic stem cell transplantation (HSCT) and the upcoming gene therapies. As a one-time intervention, the economic feasibility of HSCT makes it an attractive option for treating these disorders, especially in lower and middle-income countries. Further, improvements in peri-transplantation medical care, better conditioning regimens and better supportive care have improved the outcomes of patients undergoing HSCT. In this review, we discuss the current evidence for HSCT in various storage disorders and its suitability as a mode of therapy for the developing world.

Hepatomegaly and Splenomegaly: An Approach to the Diagnosis of Lysosomal Storage Diseases

Clinical findings of hepatomegaly and splenomegaly, the abnormal enlargement of the liver and spleen, respectively, should prompt a broad differential diagnosis that includes metabolic, congestive, neoplastic, infectious, toxic, and inflammatory conditions. Among the metabolic diseases, lysosomal storage diseases (LSDs) are a group of rare and ultrarare conditions with a collective incidence of 1 in 5000 live births. LSDs are caused by genetic variants affecting the lysosomal enzymes, transporters, or integral membrane proteins. As a result, abnormal metabolites accumulate in the organelle, leading to dysfunction. Therapeutic advances, including early diagnosis and disease-targeted management, have improved the life expectancy and quality of life of people affected by certain LSDs. To access these new interventions, LSDs must be considered in patients presenting with hepatomegaly and splenomegaly throughout the lifespan. This review article navigates the diagnostic approach for individuals with hepatosplenomegaly particularly focusing on LSDs. We provide hints in the history, physical exam, laboratories, and imaging that may identify LSDs. Additionally, we discuss molecular testing, arguably the preferred confirmatory test (over biopsy), accompanied by enzymatic testing when feasible.

Donor bone marrow-derived macrophage engraftment into the central nervous system of patients following allogeneic transplantation

Hematopoietic stem cell transplantation is a well-known treatment for hematologic malignancies, wherein nascent stem cells provide regenerating marrow and immunotherapy against the tumor. The progeny of hematopoietic stem cells also populate a wide spectrum of tissues, including the brain, as bone marrow-derived macrophages similar to microglial cells. We developed a sensitive and novel combined immunohistochemistry (IHC) and XY fluorescence in situ hybridization assay to detect, quantify, and characterize donor cells in the cerebral cortices of 19 female patients who underwent allogeneic stem cell transplantation. We showed that the number of male donor cells ranged from 0.14% to 3.0% of the total cells or from 1.2% to 25% of microglial cells. Using tyramide-based fluorescent IHC, we found that at least 80% of the donor cells expressed the microglial marker ionized calcium-binding adapter molecule-1, consistent with bone marrow-derived macrophages. The percentage of donor cells was related to pretransplantation conditioning; donor cells from radiation-based myeloablative cases averaged 8.1% of microglial cells, whereas those from nonmyeloablative cases averaged only 1.3%. The number of donor cells in patients conditioned with busulfan- or treosulfan-based myeloablation was similar to that in total body irradiation-based conditioning; donor cells averaged 6.8% of the microglial cells. Notably, patients who received multiple transplantations and those with the longest posttransplantation survival had the highest level of donor engraftment, with donor cells averaging 16.3% of the microglial cells. Our work represents the largest study characterizing bone marrow-derived macrophages in patients after transplantation. The efficiency of engraftment observed in our study warrants future research on microglial replacement as a therapeutic option for disorders of the central nervous system.

Low α-N-acetylgalactosaminidase plasma concentration correlates with the presence and severity of the bipolar affective disorder

OBJECTIVES

Believing that a neurodevelopmental pathology may cause bipolar affective disorder (BAD), we aimed to measure the concentrations of α-N-acetylgalactosaminidase (α-NAGAL), a lysosomal enzyme.

METHODS

The study included 32 patients with BAD and 32 healthy controls. The Young Mania Rating Scale was used to measure the severity of the disease. Serum α-N-acetylgalactosaminidase concentrations were measured in all blood samples using the human α-N-acetylgalactosaminidase ELISA Kit.

RESULTS

A statistically significant difference was found in the α-NAGAL values between the groups. The mean α-NAGAL values of BAD patients are lower than the mean α-NAGAL values of the control group. A strong negative and statistically significant relationship was found between the α-NAGAL values of patients with BAD and their Young Mania Rating Scale scores. And a positive strong correlation was found between the age of onset of the disease and α-NAGAL levels.

CONCLUSIONS

Low α-N-acetylgalactosaminidase concentrations may cause the accumulation of some glycoproteins in the lysosomes in the brain during the gestational period, producing the clinical symptoms of BAD. α-N-acetylgalactosaminidase deficiency may not be the only cause of BAD, but it may be an important factor in the aetiology of this disease.

Could low α-N-acetylgalactosaminidase plasma concentration cause schizophrenia?

OBJECTIVES

Using a neurodevelopmental approach to examine the aetiology, we predicted an enzyme deficiency to exist at the cellular level and aimed to measure α-N-acetylgalactosaminidase (α-NAGAL) blood levels.

METHODS

The study included 32 patients diagnosed with schizophrenia and 30 healthy controls. The positive and negative syndrome scale (PANSS) was applied to the patients with schizophrenia. Serum α-NAGAL concentrations were measured in blood samples taken from all participants using the human alpha-N-acetylgalactosaminidase ELISA Kit.

RESULTS

The mean α-NAGAL values of schizophrenic patients are lower than the mean α-NAGAL values of the control group (p = 0.000 < 0.001). Correlation analysis showed that there was a significant relationship between α-NAGAL values and PANSS scores of patients with schizophrenia. PANSS total (r = -0.708, p = 0.000 < 0.001), PANSS positive (r = -0.627, p = 0.000 < 0.001), PANSS negative (r = -0.386, p = 0.029 < 0.05). And a positive moderate correlation was found between the age of onset of the disease and α-NAGAL levels (r = 0.529, p = 0.002 < 0.05).

CONCLUSIONS

Based on the neurodevelopmental hypothesis, the low α-NAGAL concentrations this study found might cause accumulation of glycoproteins in the lysosomes in the central nervous system during the gestational period and then might result in the clinical symptoms of schizophrenia. α-NAGAL may be an important factor in the aetiology of schizophrenia.

Die α-Mannosidose: eine seltene, aber unterdiagnostizierte Erkrankung?

Bei der α‑Mannosidose handelt es sich um eine seltene lysosomale Speichererkrankung, bedingt durch eine autosomal-rezessiv vererbte Defizienz der α‑Mannosidase. Die Erkrankung weist ein breites klinisches Spektrum mit chronisch progredientem Verlauf auf. Charakteristische klinische Zeichen in den ersten Lebensjahren sind Hörminderung, Entwicklungsverzögerung, rezidivierende Infekte und/oder faziale Dysmorphie. Im weiteren Verlauf der Erkrankung manifestieren sich zunehmende skeletale Probleme und eine Ataxie, beide zu Immobilität führend. Im Gegensatz zu anderen lysosomalen Speichererkrankungen zeigt sich nach dem 20. Lebensjahr meist kein weiterer Verlust kognitiver Fähigkeiten. Ab dem Alter von 15 Jahren entwickeln ca. 25 % der Patienten psychiatrische Symptome. Aufgrund der Seltenheit der Erkrankung werden viele Patienten verspätet, z. T. erst im Erwachsenenalter, diagnostiziert.

Mittlerweile stehen 2 Therapieoptionen zur Behandlung der α‑Mannosidose zur Verfügung. Bei frühzeitiger Diagnosestellung ist die hämatopoetische Stammzelltransplantation eine wichtige therapeutische Option mit potenziell positivem Effekt auf die neurokognitive Entwicklung. Die Enzymersatztherapie mit Velmanase alfa ist seit 2018 in Europa zugelassen und eine therapeutische Option zur Behandlung der nichtneurologischen Manifestationen bei α‑Mannosidose. Sie hat jedoch keinen Einfluss auf neurologische Manifestationen der Erkrankung.

Zur Verbesserung der Diagnostik von Kindern und Jugendlichen mit der seltenen Erkrankung α‑Mannosidose möchte dieser Beitrag das Wissen um und das Bewusstsein für diese Erkrankung schärfen. Die frühe Diagnose einer α‑Mannosidose erspart nicht nur den Familien einen jahrelangen diagnostischen Leidensweg, sondern ermöglicht auch den betroffenen Patienten ein verbessertes Auskommen durch einen frühen Therapiestart.

An unusual presentation of fucosidosis in a Chinese boy: a case report and literature review (childhood fucosidosis)

Background

Fucosidosis is one of the rare autosomal recessive lysosomal storage diseases (LSDs) attributed to FUCA1 variants causing the deficiency of α-L-fucosidase in vivo. Α-L-fucosidase deficiency will cause excessive accumulation of fucosylated glycoproteins and glycolipids, which eventually leads to dysfunction in all tissue systems and presents with multiple symptoms. Fucosidosis is a rare disease which is approximately 120 cases have been reported worldwide (Wang, L. et al., J Int Med Res 48, 1-6, 2020). The number of reported cases in China is no more than 10 (Zhang, X. et al., J Int Med Res 49:3000605211005975, 2021).

Case presentation

The patient was an 8-year-old Chinese boy who presented with postnatal motor retardation, intellectual disability, short stature, language development retardation, coarse facial features, hepatomegaly, and diffuse angiokeratoma of both palms. His genetic testing showed the presence of a homozygous pathogenic variant (c.671delC) in the FUCA1 gene. In addition, the enzymatic activity of α-L-fucosidase was low. Ultimately, the patient was diagnosed with fucosidosis.

Conclusions

Fucosidosis is a rare lysosomal storage disease because of FUCA1 variants that cause the deficiency of α-L-fucosidase in vivo. An explicit diagnosis requires a combination of clinical manifestations, imaging examination, genetic testing and enzyme activity analysis. Early diagnosis plays an important role in fucosidosis.

Is hematopoietic stem cell transplantation a therapeutic option for mucolipidosis type II?

BACKGROUND

Mucolipidosis type II (MLII) is an ultra-rare lysosomal storage disorder caused by defective lysosomal enzyme trafficking. Clinical hallmarks are craniofacial dysmorphia, cardiorespiratory dysfunction, hepatosplenomegaly, skeletal deformities and neurocognitive retardation. Death usually occurs in the first decade of life and no cure exists. Hematopoietic stem cell transplantation (HSCT) has been performed in few MLII patients, but comprehensive follow-up data are extremely scarce.

METHODS

MLII diagnosis was confirmed in a female three-month-old patient with the mutations c.2213C > A and c.2220_2221dup in the GNPTAB gene. At nine months of age, the patient received HSCT from a 9/10 human leukocyte antigen (HLA)-matched unrelated donor.

RESULTS

HSCT resulted in a sustained reduction of lysosomal storage und bone metabolism markers. At six years of age, the patient showed normal cardiac function, partial respiratory insufficiency and moderate hepatomegaly, whereas skeletal manifestations had progressed. However, the patient could walk and maintained an overall good quality of life. Neurocognitive testing revealed a developmental quotient of 36%. The patient died at 6.6 years of age following a human metapneumovirus (hMPV) pneumonia.

CONCLUSIONS

The exact benefit remains unclear as current literature vastly lacks comparable data on MLII natural history patients. In order to evaluate experimental therapies, in-depth prospective studies and registries of untreated MLII patients are indispensable.

Fucosidosis-Clinical Manifestation, Long-Term Outcomes, and Genetic Profile-Review and Case Series

Fucosidosis is a neurodegenerative disorder which progresses inexorably. Clinical features include coarse facial features, growth retardation, recurrent upper respiratory infections, dysostosis multiplex, and angiokeratoma corporis diffusum. Fucosidosis is caused by mutations in the FUCA1 gene resulting in α-L-fucosidase deficiency. Only 36 pathogenic variants in the FUCA1 gene are related to fucosidosis. Most of them are missense/nonsense substitutions; six missense and 11 nonsense mutations. Among deletions there were eight small and five gross changes. So far, only three splice site variants have been described—one small deletion, one complete deletion and one stop-loss mutation. The disease has a significant clinical variability, the cause of which is not well understood. The genotype–phenotype correlation has not been well defined. This review describes the genetic profile and clinical manifestations of fucosidosis in pediatric and adult cases.

Mucolipidoses Overview: Past, Present, and Future

Mucolipidosis II and III (ML II/III) are caused by a deficiency of uridine-diphosphate N-acetylglucosamine: lysosomal-enzyme-N-acetylglucosamine-1-phosphotransferase (GlcNAc-1-phosphotransferase, EC2.7.8.17), which tags lysosomal enzymes with a mannose 6-phosphate (M6P) marker for transport to the lysosome. The process is performed by a sequential two-step process: first, GlcNAc-1-phosphotransferase catalyzes the transfer of GlcNAc-1-phosphate to the selected mannose residues on lysosomal enzymes in the cis-Golgi network. The second step removes GlcNAc from lysosomal enzymes by N-acetylglucosamine-1-phosphodiester α-N-acetylglucosaminidase (uncovering enzyme) and exposes the mannose 6-phosphate (M6P) residues in the trans-Golgi network, in which the enzymes are targeted to the lysosomes by M6Preceptors. A deficiency of GlcNAc-1-phosphotransferase causes the hypersecretion of lysosomal enzymes out of cells, resulting in a shortage of multiple lysosomal enzymes within lysosomes. Due to a lack of GlcNAc-1-phosphotransferase, the accumulation of cholesterol, phospholipids, glycosaminoglycans (GAGs), and other undegraded substrates occurs in the lysosomes. Clinically, ML II and ML III exhibit quite similar manifestations to mucopolysaccharidoses (MPSs), including specific skeletal deformities known as dysostosis multiplex and gingival hyperplasia. The life expectancy is less than 10 years in the severe type, and there is no definitive treatment for this disease. In this review, we have described the updated diagnosis and therapy on ML II/III.