Infantile neurological Gaucher's disease in three siblings. An ultrastructural study

Neuronal accumulation of glucosylceramide in a mouse model of neuronopathic Gaucher disease leads to neurodegeneration

Gaucher disease has recently received wide attention due to the unexpected discovery that it is a genetic risk factor for Parkinson's disease. Gaucher disease is caused by the defective activity of the lysosomal enzyme, glucocerebrosidase (GCase; GBA1), resulting in intracellular accumulation of the glycosphingolipids, glucosylceramide and psychosine. The rare neuronopathic forms of GD (nGD) are characterized by profound neurological impairment and neuronal cell death. We have previously described the progression of neuropathological changes in a mouse model of nGD. We now examine the relationship between glycosphingolipid accumulation and initiation of pathology at two pre-symptomatic stages of the disease in four different brain areas which display differential degrees of susceptibility to GCase deficiency. Liquid chromatography electrospray ionization tandem mass spectrometry demonstrated glucosylceramide and psychosine accumulation in nGD brains prior to the appearance of neuroinflammation, although only glucosylceramide accumulation correlated with neuroinflammation and neuron loss. Levels of other sphingolipids, including the pro-apoptotic lipid, ceramide, were mostly unaltered. Transmission electron microscopy revealed that glucosylceramide accumulation occurs in neurons, mostly in the form of membrane-delimited pseudo-tubules located near the nucleus. Highly disrupted glucosylceramide-storing cells, which are likely degenerating neurons containing massive inclusions, numerous autophagosomes and unique ultrastructural features, were also observed. Together, our results indicate that a certain level of neuronal glucosylceramide storage is required to trigger neuropathological changes in affected brain areas, while other brain areas containing similar glucosylceramide levels are unaltered, presumably because of intrinsic differences in neuronal properties, or in the neuronal environment, between various brain regions.

Glucosylceramide transfer from lysosomes--the missing link in molecular pathology of glucosylceramidase deficiency: a hypothesis based on existing data

Gaucher disease (GD), deficiency of acid glucosylceramidase (GlcCer-ase) is characterized by deficient degradation of beta-glucosylceramide (GlcCer). It is well known that, in GD, the lysosomal accumulation of uncleaved GlcCer is limited to macrophages, which are gradually converted to storage cells with well known cytology--Gaucher cells (GCs). On the basis of previous studies of the disorder and of a comparison with other lysosomal enzymopathies affecting degradation of the GlcCer-based glycosphingolipid series, it is hypothesized that in other cell types (i.e. non-macrophage cells) the uncleaved GlcCer, in GlcCer-ase deficiency, is transferred to other cell compartments, where it may be processed and even accumulated to various degrees. The consequence of the abnormal extralysosomal load may differ according to the cell type and compartment targeted and may be influenced by genetically determined factors, by a number of acquired conditions, including the current metabolic situation. The sequelae of the uncleaved GlcCer extralysosomal transfer may range from probably innocent or positive stimulatory, to the much more serious, in which it interferes with a variety of cell functions, and in extreme cases, can lead to cell death. This alternative processing of uncleaved GlcCer may help to explain tissue alterations seen in GD that have, so far, resisted explanation based simply on the presence of GCs. Paralysosomal alternative processing may thus go a long way towards filling a long-standing gap in the understanding of the molecular pathology of the disorder. The impact of this alternative process will most likely be inversely proportional to the level of residual GlcCer-ase activity. Lysosomal sequestration of GlcCer in these cells is either absent or in those exceptional cases where it does occur, it is exceptional and rudimentary. It is suggested that paralysosomal alternative processing of uncleaved GlcCer is the main target for enzyme replacement therapy. The mechanism responsible for GlcCer transfer remains to be elucidated. It may also help in explaining the so far unclear origin of glucosylsphingosine (GlcSph) and define the mutual relation between these two processes.

Perinatal lethal phenotype with generalized ichthyosis in a type 2 Gaucher disease patient with the [L444P;E326K]/P182L genotype: effect of the E326K change in neonatal and classic forms of the disease

Gaucher disease, the most common lysosomal storage disorder, encompasses a wide spectrum of clinical symptoms. The perinatal lethal form is very rare and is considered a distinct form of classic type 2 Gaucher disease. Prominent features of the severe perinatal form are hepatosplenomegaly variable, associated with hydrops fetalis and ichthyosis. Here, we describe a child who presented generalized ichthyosis and died at 25 days of age. Genotype analysis revealed compound heterozygosity for the complex allele [L444P;E326K] and mutation P182L, described for the first time in this patient. Mutations E326K and L444P were on the same chromosome. Expression studies of mutant glucocerebrosidases showed that the double mutant allele had lower activity, 8.5% of wild type, in contrast to the activity of individual E326K and L444P mutant enzymes, 42.7% and 14.1%, respectively. The P182L mutant enzyme showed no glucocerebrosidase activity. A revision of the genotypes identified in a series of Spanish patients with type 2 Gaucher disease showed that the complex allele [L444P;E326K] accounted for 19.2% of patient alleles and that homozygosity for this allele or its heterozygosity with mutation L444P, or another severe mutation such as P182L, was associated with the perinatal lethal presentation of the disease. In contrast, the [L444P;E326K] allele was not detected in patients with classic type 2 diagnosed when several months old. The high frequency of the E326K substitution observed in patients with type 2 as compared to the general population (0.5%) suggests that this change may have a modulating negative effect on the clinical condition of these Gaucher disease patients when present in combination with mutation L444P. The relatively high prevalence of the double mutant allele in Spanish patients prompted us to perform a haplotype analysis, using four polymorphic markers, which suggest a common origin for this allele. During the mutational analysis of the series of type 2 patients, a novel mutation, I260T (c.896T>C), was identified.

Type 2 Gaucher disease: 15 new cases and review of the literature

OBJECTIVES

To provide a description of type 2 Gaucher disease. To attempt to define type 2 Gaucher disease within the spectrum of early-onset neuronopathic Gaucher disease.

BACKGROUND

Type 2 Gaucher disease is a rare disorder due to glucocerebrosidase deficiency that comprises a rapidly progressing neurological degeneration associated with visceral signs. Most data collected rely on the description of single cases or siblings. Cases of perinatal-lethal Gaucher disease are frequently considered as type 2 Gaucher patients, though the clinical presentation is different.

METHODS

We retrospectively studied the clinical history of 15 original acute Gaucher disease patients and reviewed the available data of 104 published cases of early-onset neuronopathic Gaucher disease, including 61 patients with the acute type and 43 cases of the perinatal-lethal form.

RESULTS

The neurological presentation of type 2 Gaucher disease is homogeneous and characterized by precocious, severe, and rapidly progressive brainstem degeneration in the foreground. The most frequent initial signs are hyperextension of the neck, swallowing impairment, and strabismus. Provoked asphyxic episodes generally appear in a second time. They are followed by prolonged spontaneous apneas that seem to be the main pejorative feature. Other neurological signs may be observed, but epilepsy, myoclonic epilepsy/myoclonus, trismus, stridor, and progressive microcephaly are less characteristic. Psychomotor regression may occur, but is not a typical feature of the disease onset. Chronic or subacute pulmonary disease predominates in the visceral involvement. Hepatosplenomegaly, failure to thrive, thrombocytopenia, and anemia are the other remarkable, albeit non-specific, features. The inflammatory component of Gaucher disease is underlined by the addition of unexplained fever to this systemic clinical picture. The natural history and particular signs of perinatal-lethal Gaucher disease do not belong to the type 2 Gaucher disease phenotype.

CONCLUSION

Type 2 Gaucher disease is a clinically homogeneous entity. The specificity of the neurological involvement is sufficient to suspect the diagnosis at the onset of the disease. Type 2 and perinatal-lethal Gaucher diseases are easily distinguishable in most cases.

Perinatal-lethal Gaucher disease

Gaucher disease is a lysosomal storage disease caused by glucocerebrosidase deficiency. Although purely visceral in most cases, some Gaucher disease patients have neurological signs. Signs of Gaucher disease appear after a symptom-free period, except in rare cases with fetal onset. The description of such cases was based mainly on single reports and siblings. We report here a series of perinatal-lethal Gaucher disease cases highlighting the specificity of this phenotype. We retrospectively studied eight original cases of proven Gaucher disease with fetal onset. Non-immune hydrops fetalis was present in all cases but one, and associated with hepatosplenomegaly, ichthyosis, arthrogryposis, and facial dysmorphy. The similarities between our cases and 33 previously described cases allow us to better delineate the perinatal-lethal Gaucher disease phenotype. Hydrops fetalis, in utero fetal death and neonatal distress are prominent features. When hydrops is absent, neurological involvement begins in the first week and leads to death within three months. Hepatosplenomegaly is a major sign, and associated with ichthyosis, arthrogryposis, and facial dysmorphy in some 35-43% of cases. Perinatal-lethal Gaucher disease is a specific entity defined by its particular course and signs that are absent in classical type 2 Gaucher disease. Our study provides clues to the diagnosis of this likely underdiagnosed condition, which must be biochemically confirmed in order to propose appropriate genetic counselling.

[Diagnosis of metabolic diseases of the nervous system in children through ultrastructural analysis of non cerebral tissue]

Although biochemical and molecular genetic analysis are the most precise methods for the diagnosis of metabolic diseases, morphological studies remain a very important diagnostic method mainly in countries like Brazil, where clinical laboratories are unable to perform most of the exams required for the diagnosis of these diseases. Moreover, pathologic evaluation is the single diagnostic method for some disorders whose metabolic defect is unknown such as neuronal ceroid-lipofuscinosis, infantile neuroaxonal dystrophy or Lafora disease. We present our experience with ultrastructural analysis in 582 exams of ocular conjunctiva (n = 320), skin (n = 92) or peripheral nerve (n = 170) performed between 1975 and 1996, in 486 children. In 112 cases there were definite ultrastructural changes. In 59 cases, the sole ultrastructural exam allowed the diagnosis. In 29, the changes were less specific, and the final diagnosis was performed by a combination of clinical and pathological analysis. In the remaining 24 cases, a generic diagnosis of mucopolysaccharidosis was done in 8 cases, oligosaccharidosis in 4 cases and GM2 gangliosidosis in 12 cases. Whenever a biochemical test was performed in overseas laboratories, the initial diagnosis was confirmed. These results stress the importance of ultrastructural analysis in non-cerebral tissues for the diagnosis of many metabolic disorders mainly when biochemical tests cannot be performed.

A biochemical and ultrastructural evaluation of the type 2 Gaucher mouse

Gaucher mice, created by targeted disruption of the glucocerebrosidase gene, are totally deficient in glucocerebrosidase and have a rapidly deteriorating clinical course analogous to the most severely affected type 2 human patients. An ultrastructural study of tissues from these mice revealed glucocerebroside accumulation in bone marrow, liver, spleen, and brain. This glycolipid had a characteristic elongated tubular structure and was contained in lysosomes, as demonstrated by colocalization with both ingested carbon particles and cathepsin D. In the central nervous system (CNS), glucocerebroside was diffusely stored in microglia cells and in brainstem and spinal cord neurons, but not in neurons of the cerebellum or cerebral cortex. This rostralcaudal pattern of neuronal lipid storage in these Gaucher mice replicates the pattern seen in type 2 human Gaucher patients and clearly demonstrates that glycosphingolipid catabolism and/or accumulation varies within different brain regions. Surprisingly, the cellular pathology of tissue from these Gaucher mice was relatively mild, and suggests that the early and rapid demise of both Gaucher mice and severely affected type 2 human neonates may be the result of both a neurotoxic metabolite, such as glucosylsphingosine, and other factors, such as skin water barrier dysfunction secondary to the absence of glucocerebrosidase activity.

Sphingolipid activator protein deficiency in a 16-week-old atypical Gaucher disease patient and his fetal sibling: biochemical signs of combined sphingolipidoses

We describe a patient who presented shortly after birth with hyperkinetic behaviour, myoclonia, respiratory insufficiency and hepatosplenomegaly. Gaucher-like storage cells were found in bone marrow. A liver biopsy showed massive lysosomal storage morphologically different to that in known lipid storage disorders. Biochemically, the patient had partial deficiencies of beta-galactocerebrosidase, beta-glucocerebrosidase and ceramidase in skin fibroblast extracts, but the sphingomyelinase activity was normal. Glucosyl ceramide and ceramide were elevated in liver tissue. Loading of cultured fibroblasts with radioactive sphingolipid precursors indicated a profound defect in ceramide catabolism. Immunological studies in fibroblasts showed a total absence of cross-reacting material to sphingolipid activator protein 2 (SAP-2). The patient died at 16 weeks of age. The fetus from his mother's next pregnancy was similarly affected. The possibility that the disorder results from a primary defect at the level of SAP-2 is discussed. We have named this unique disorder SAP deficiency.

Infantile Gaucher's disease: a case with neuronal storage

The brain of a 17-month-old boy with infantile Gaucher's disease and oculomotor apraxia was studied by light and electron microscopy. Light microscopic examination showed large perivascular accumulations of Gaucher's cells in frontal lobe white matter, severe neuronal loss in the calcarine cortex and dentate nucleus of the cerebellum, and neuronophagia and microglial nodules in the brainstem. Electron microscopy demonstrated intraneuronal cytoplasmic inclusions containing twisted tubules characteristic of Gaucher's disease in both the oculomotor nucleus and a random sample of cortex.

Type 2 and type 3 Gaucher disease: a morphological and biochemical study

Glucocerebroside levels were measured in the brains of patients with neuronopathic forms (types 2 and 3) of Gaucher disease and compared to those obtained from control brain. Nine separate brain regions (frontal, temporal, occipital, and cerebellar cortices; thalamus; corpus striatum; pons; medulla; and dentate nuclei) were analyzed. In all the Gaucher brains studied, the greatest glucocerebroside accumulation occurred within the occipital cortex, with lesser amounts in the temporal and frontal areas. The cerebellar cortex, corpus striatum, and thalamus in Gaucher brains had mildly increased levels of glucocerebroside, especially when the values were expressed as a percentage of total non-hydroxy fatty-acid cerebroside. Brainstem structures (pons and medulla) and dentate nuclei did not have increased glucocerebroside levels when compared to levels from similar control areas. However, when glucocerebroside concentration was expressed as a percentage of total non-hydroxy fatty-acid cerebroside, the type 2 Gaucher brainstem structures did show a slight increase in glucocerebroside levels over control levels. Neuropathological studies demonstrated the presence of Gaucher cells, gliosis, and microglial nodules within the type 2 brains. The neuropathological findings correlated with the glucocerebroside accumulation in the type 2 brains. Despite the similar pattern of glucocerebroside accumulation in the type 3 brain, no neuropathological abnormalities were seen. Thus, this study demonstrated that within several brain regions, both neuronopathic forms of Gaucher disease have elevated glucocerebroside levels, and that in the type 2 brains, the glucocerebroside accumulation correlated positively with the neuropathological findings.