Chorionic villus ultrastructure in type II glycogen storage disease (Pompe's disease)

Mucolipidosis Type II Affecting 1 Fetus and Placental Disk of a Dichorionic-Diamnionic Twin Gestation: A Case Report and Review of the Literature

Mucolipidosis type II, also known as I-cell disease, is an autosomal recessive inborn error of metabolism, resulting from loss-of-function mutations in GNPTAB. Affected infants exhibit multiple physical anomalies and developmental delay, and death from disease follows in early childhood. Here we present an instructive case of mucolipidosis type II affecting 1 fetus and placental disk in a dichorionic-diamnionic twin pregnancy delivered at 36-wk gestation. The second twin and placental disk showed no abnormality. On microscopic examination, the affected placenta displayed marked vacuolization of the syncytiotrophoblast and Hofbauer cells, which was confirmed on ultrastructural examination. To our knowledge, this is the first description of placental findings in a twin pregnancy, wherein only 1 twin is affected by an inborn error of metabolism. This provides an opportunity to highlight the placental abnormalities seen in this group of diseases, and to emphasize the role of pathologic examination in early detection of otherwise unsuspected inborn errors of metabolism.

Skeletal muscle pathology of infantile Pompe disease during long-term enzyme replacement therapy

Background

Pompe disease is an autosomal recessive metabolic neuromuscular disorder caused by a deficiency of the lysosomal enzyme acid alpha-glucosidase (GAA). It has long been believed that the underlying pathology leading to tissue damage is caused by the enlargement and rupture of glycogen-filled lysosomes. Recent studies have also implicated autophagy, an intracellular lysosome-dependent degradation system, in the disease pathogenesis. In this study, we characterize the long-term impact of enzyme replacement therapy (ERT) with recombinant human GAA (rhGAA) on lysosomal glycogen accumulation and autophagy in some of the oldest survivors with classic infantile Pompe disease (IPD).

Methods

Muscle biopsies from 8 [4 female, 4 male; 6 cross-reactive immunologic material (CRIM)-positive, 2 CRIM-negative] patients with a confirmed diagnosis of classic IPD were examined using standard histopathological approaches. In addition, muscle biopsies were evaluated by immunostaining for lysosomal marker (lysosomal-associated membrane protein-2; LAMP2), autophagosomal marker (microtubule-associated protein 1 light chain 3; LC3), and acid and alkaline ATPases. All patients received rhGAA by infusion at cumulative biweekly doses of 20–40 mg/kg.

Results

Median age at diagnosis of classic IPD was 3.4 months (range: 0 to 6.5 months; n = 8). At the time of muscle biopsy, the patients’ ages ranged from 1 to 103 months and ERT duration ranged from 0 (i.e., baseline, pre-ERT) to 96 months. The response to therapy varied considerably among the patients: some patients demonstrated motor gains while others experienced deterioration of motor function, either with or without a period of initial clinical benefit. Skeletal muscle pathology included fiber destruction, lysosomal vacuolation, and autophagic abnormalities (i.e., buildup), particularly in fibers with minimal lysosomal enlargement. Overall, the pathology reflected clinical status.

Conclusions

This is the first study to investigate the impact of rhGAA ERT on lysosomal glycogen accumulation and autophagic buildup in patients with classic IPD beyond 18 months of treatment. Our findings indicate that ERT does not fully halt or reverse the underlying skeletal muscle pathology in IPD. The best outcomes were observed in the two patients who began therapy early, namely at 0.5 and 1.1 months of age.

Autophagy and mitochondria in Pompe disease: nothing is so new as what has long been forgotten

Macroautophagy (often referred to as autophagy) is an evolutionarily conserved intracellular system by which macromolecules and organelles are delivered to lysosomes for degradation and recycling. Autophagy is robustly induced in response to starvation in order to generate nutrients and energy through the lysosomal degradation of cytoplasmic components. Constitutive, basal autophagy serves as a quality control mechanism for the elimination of aggregated proteins and worn-out or damaged organelles, such as mitochondria. Research during the last decade has made it clear that malfunctioning or failure of this system is associated with a wide range of human pathologies and age-related diseases. Our recent data provide strong evidence for the role of autophagy in the pathogenesis of Pompe disease, a lysosomal glycogen storage disease caused by deficiency of acid alpha-glucosidase (GAA). Large pools of autophagic debris in skeletal muscle cells can be seen in both our GAA knockout model and patients with Pompe disease. In this review, we will focus on these recent data, and comment on the not so recent observations pointing to the involvement of autophagy in skeletal muscle damage in Pompe disease.

Chorionic villi ultrastructure in the prenatal diagnosis of glycogenosis type II

OBJECTIVE

To perform the ultrastructural examination of a chorionic villi biopsy as a predictor of foetal involvement in the infantile form of glycogenosis type II (Pompe disease).

METHODS

Ultrastructural, biochemical and genetic analyses were performed on chorionic villi biopsies of three consecutive pregnancies in a woman with a previous child affected by Pompe disease.

RESULTS

In the only affected foetus, glycogen storage was observed in fibrocytes and endothelial cells of a chorionic villi sample at 11 week's gestation. Severe multi-organ involvement was demonstrated in the tissues of the aborted foetus. No abnormal material was found in the chorionic samples of two subsequent pregnancies, and a healthy boy and girl were born at term and remain unaffected. Both exhibited a partial reduction in acid maltase and were carriers of the maternal mutation.

CONCLUSIONS

Ultrastructural findings correlated with biochemical and genetic results, providing a clear and early indicator of the definite diagnosis for future pregnancy management or an early therapeutic approach.

Prenatal diagnosis of lysosomal storage diseases

The prenatal diagnosis of lysosomal storage disorders can be achieved, once the diagnosis is confirmed in the index case, by a variety of techniques including analysis of amniotic fluid, asay of enzymic activity in cultured amniotic fluid cells, cultured chorionic villus cells and by direct assay of activity in chorionic villus samples. These studies can be accompanied by ultrastructural observations which give an independent means of diagnosis. In some instances molecular genetic studies for mutation detection or linkage analysis are appropriate for prenatal diagnosis. Pseudodeficiencies of some of the lysosomal enzymes, which cause no clinical problems, can complicate the initial diagnosis particularly in metachromatic leucodystrophy where the pseudodeficiency is more common than the disease itself. Mutation analysis as well as enzyme assay is necessary not only in the index case but also in the parents before the same techniques are applied to a sample for prenatal diagnosis. A large number of lysosomal storage disorders may present as fetal hydrops and the diagnosis can be established at this late stage by fetal blood sampling and examination by microscopy as well as by biochemical assay of the appropriate enzyme or metabolite in amniotic fluid. All prenatal diagnoses in which an affected fetus is indicated should have confirmation of the diagnosis as soon as possible to reassure anxious parents, and to act as audit of the laboratory's competence to undertake prenatal diagnosis. A combined approach to prenatal diagnosis involving biochemical, molecular genetic and morphological studies is recommended.

Extracerebral biopsy in lysosomal and peroxisomal disorders. Ultrastructural findings

The lysosomal and peroxisomal disorders are characterized by specific storage affecting mainly the central nervous system with involvement of the peripheral nervous system and visceral organs. Most of these disorders can now be diagnosed by using biochemical and enzymatical assays and by molecular biology techniques, without the need for a brain biopsy used previously. Extraneural tissue biopsies have also been investigated at the ultrastructural level. The study of such tissues is still necessary when the enzymatic or biochemical defect remains unknown and when DNA studies are not informative. The choice of tissue is important. Skin and conjunctival biopsies are less traumatic and are cost-effective diagnostic tools allowing the examination of a great diversity of structures. Skeletal muscle and peripheral nerves are more frequently used for patients with a late-onset or slower course of disease. Rectal biopsy is helpful when neurons require examination in lysosomal diseases, whereas liver is more usually investigated than adrenal or testis in peroxisomal diseases. Bone marrow is most useful for Gaucher's disease while lymphocytes may be examined for all lysosomal disorders as a first diagnostic approach. Chorionic villi still have a diagnostic role in combination of electron microscopy with DNA studies in early pregnancies at-risk for neuronal ceroid lipofuscinosis. Cultured fibroblasts are less informative than other biopsy samples for the morphological evaluation of lysosomal and peroxisomal disorders.

Prenatal diagnosis of Pompe disease by electron microscopy

INTRODUCTION

Pompe disease is one of the lysosomal storage disorders caused by alpha-glucosidase deficiency. The disease is characterized by accumulation of glycogen in the lysosome. The accumulation has unique ultrastructural features, which enable a prenatal diagnosis possible by electron microscopy.

MATERIALS AND METHODS

A prenatal diagnosis of Pompe disease by electron microscopic study of chorionic villus biopsies is described in a fetus of a mother whose previous child had died of the disease.

RESULTS

Electron microscopy revealed fibrocytes with typical vacuoles filled with glycogen. A prenatal diagnosis of Pompe disease was made and subsequently confirmed by the autopsy study of the abortus.

CONCLUSION

We report the usefulness of electron microscopy for prenatal diagnosis in the first trimester of Pompe disease.

Hydrocephalus associated with glycogen storage disease type II (Pompe's disease)

The authors describe a case of hydrocephalus in an 8-month, 2-week-old infant who had been previously diagnosed with glycogen storage disease type II. Cranial imaging revealed no evidence of obstruction within the ventricular system. This case adds to the central nervous system complications associated with this disorder. Several possible mechanisms for the hydrocephalus observed in this infant are discussed.

Prenatal diagnosis of Pompe's disease (type II glycogenosis) in chorionic villus biopsy using maltose as a substrate

Uncultured trophoblasts obtained from chorionic villus biopsy during the gestation period of 8-12 weeks were assayed for alpha-glucosidase activity using maltose as the substrate. Only one major form of maltase activity with a pH optimum at 4.0 was demonstrated. Using this method, we performed prenatal diagnosis on three pregnancies at risk for the infantile form of type II glycogen storage disease. Two affected fetuses and one unaffected fetus were predicted and the diagnosis was subsequently confirmed. The maltose assay offered a direct, simple, and sensitive method for prenatal diagnosis of Pompe's disease in the first trimester.