Adult Sandhoff disease with 2 mutations in the HEXB gene presenting as brachial amyotrophic diplegia

Lysosomal storage disorders identified in adult population from India: Experience of a tertiary genetic centre and review of literature

Lysosomal storage disorders (LSDs) in adults have milder phenotype and variable age at presentation. Several studies have described the phenotype, genotype and treatment outcomes for adult-onset LSDs like Gaucher, Fabry, Pompe disease and others. We describe the first systematic study on the occurrence of LSDs in an adult population from India. It describes, the key clinical signs seen in these patients and those from literature review that can aid in early detection. Of 2102 biochemically diagnosed LSDs cases, 32 adult patients were identified with LSDs. Based on the clinical suspicion, screening test and enzyme study was carried out. Twenty-two patients were subjected to a genetic study to identify the causative variant in a respective gene. Of the 32 adult patients, we observed a maximum percentage of 37.5% (n = 12) cases with Gaucher disease, followed by 13% (n = 4) with Fabry disease. We found 10% of cases with MPS IVA and MPS I, and 9% cases with Pompe. Single case of adult mucolipidosis III and two cases each of Type 1 Sialidosis, Niemann-Pick disease B and metachromatic leukodystrophy were identified. We observed two common variants p.Leu483Pro and p.Ala487Thr in the GBA1 gene in 23% of Indian patients with adult Gaucher disease. No common variants were observed in other aforementioned LSDs. Study identified 50% of Fabry patients and 4% of Gaucher patients diagnosed at our centre to be adults. The prevalence of adult Pompe patients was low (3.4%) as compared to 80% reported in the Caucasian population. Adult LSDs such as, MPS III, GM1/GM2 gangliosidosis and Krabbe disease were not identified in our cohort.

Adult-onset non-5q proximal spinal muscular atrophy: a comprehensive review

BACKGROUND

Adult-onset spinal muscular atrophy (SMA) represents an expanding group of inherited neurodegenerative disorders in clinical practice.

OBJECTIVE

This review aims to synthesize the main clinical, genetic, radiological, biochemical, and neurophysiological aspects related to the classical and recently described forms of proximal SMA.

METHODS

The authors performed a non-systematic critical review summarizing adult-onset proximal SMA presentations.

RESULTS

Previously limited to cases of SMN1-related SMA type 4 (adult form), this group has now more than 15 different clinical conditions that have in common the symmetrical and progressive compromise of lower motor neurons starting in adulthood or elderly stage. New clinical and genetic subtypes of adult-onset proximal SMA have been recognized and are currently target of wide neuroradiological, pathological, and genetic studies.

CONCLUSIONS

This new complex group of rare disorders typically present with lower motor neuron disease in association with other neurological or systemic signs of impairment, which are relatively specific and typical for each genetic subtype.

Late onset Sandhoff disease presenting with lower motor neuron disease and stuttering

Defects in the HEXB gene which encodes the β-subunit of β-hexosaminidase A and B enzymes, cause a GM2 gangliosidosis, also known as Sandhoff disease, which is a rare lysosomal storage disorder. The most common form of the disease lead to quickly progressing mental and motor decline in infancy; however there are other less severe forms with later onset that can also involve lower motor neurons. The diagnosis of this disease is based on low serum β-hexosaminidases A and B levels and confirmed using genetic test. We report two siblings with compound heterozygous HEXB mutations whose phenotype was extremely mild consisting in stuttering in both cases associated to mild proximal weakness in one of the cases, broadening the clinical spectrum of late onset Sandhoff disease.

Sandhoff disease in the elderly: a case study

Sandhoff disease is an infrequent, genetically caused disorder with a recessive autosomal inheritance pattern. It belongs to the gangliosidosis GM2 group and is produced by mutations in gen HEXB leading to reduction in enzymatic activity of enzymes β-hexosaminidase A and B. Adult-onset GM2 gangliosidosis is rare. Here we report a white male who presented at age 69 with a fast-progression, motor neuron disease, mimicking amyotrophic lateral sclerosis (ALS), combined with autonomic dysfunction, sensory ataxia, and exaggerated startle to noise. Enzymatic assays demonstrated deficiency of both Hexosaminidases A and B leading to the diagnosis of Sandhoff disease.

Quantitative oculomotor and nonmotor assessments in late-onset GM2 gangliosidosis

OBJECTIVE

A cross-sectional study was performed to evaluate whether quantitative oculomotor measures correlate with disease severity in late-onset GM2 gangliosidosis (LOGG) and assess cognition and sleep as potential early nonmotor features.

METHODS

Ten patients with LOGG underwent quantitative oculomotor recordings, including measurements of the angular vestibulo-ocular reflex (VOR), with results compared to age- and sex-matched controls. Disease severity was assessed by ataxia rating scales. Cognitive/neuropsychiatric features were assessed by the cerebellar cognitive affective syndrome (CCAS) scale, Cerebellar Neuropsychiatric Rating Scale, and sleep quality evaluated using subjective sleep scales.

RESULTS

Oculomotor abnormalities were found in all participants, including 3/10 with clinically normal eye movements. Abnormalities involved impaired saccadic accuracy (5/10), abnormal vertical (8/10) and horizontal (4/10) pursuit, reduced optokinetic nystagmus (OKN) responses (7/10), low VOR gain (10/10), and impaired VOR cancellation (2/10). Compared to controls, the LOGG group showed significant differences in saccade, VOR, OKN, and visually enhanced VOR gains. Severity of saccadic dysmetria, OKN, and VOR fixation-suppression impairments correlated with ataxia scales (p < 0.05). Nine out of ten patients with LOGG had evidence of the CCAS (5/10 definite, 2/10 probable, 2/10 possible). Excessive daytime sleepiness was present in 4/10 and 8/10 had poor subjective sleep quality.

CONCLUSIONS

Cerebellar oculomotor abnormalities were present in all patients with LOGG, including those with normal clinical oculomotor examinations. Saccade accuracy (dorsal cerebellar vermis localization), fixation suppression, and OKN gain (cerebellar flocculus/paraflocculus localization) correlated with disease severity, suggesting that quantitative oculomotor measurements could be used to track disease progression. We found evidence of the CCAS, suggesting that cerebellar dysfunction may explain the cognitive disorder in LOGG. Sleep impairments were prevalent and require further study.

Emerging links between pediatric lysosomal storage diseases and adult parkinsonism

Lysosomal storage disorders comprise a clinically heterogeneous group of autosomal-recessive or X-linked genetic syndromes caused by disruption of lysosomal biogenesis or function resulting in accumulation of nondegraded substrates. Although lysosomal storage disorders are diagnosed predominantly in children, many show variable expressivity with clinical presentations possible later in life. Given the important role of lysosomes in neuronal homeostasis, neurological manifestations, including movement disorders, can accompany many lysosomal storage disorders. Over the last decade, evidence from genetics, clinical epidemiology, cell biology, and biochemistry have converged to implicate links between lysosomal storage disorders and adult-onset movement disorders. The strongest evidence comes from mutations in Glucocerebrosidase, which cause Gaucher's disease and are among the most common and potent risk factors for PD. However, recently, many additional lysosomal storage disorder genes have been similarly implicated, including SMPD1, ATP13A2, GALC, and others. Examination of these links can offer insight into pathogenesis of PD and guide development of new therapeutic strategies. We systematically review the emerging genetic links between lysosomal storage disorders and PD. © 2019 International Parkinson and Movement Disorder Society.

Motor neuron disease in inherited neurometabolic disorders

Inherited neurometabolic disorders represent a growing group of inborn errors of metabolism that present with major neurological symptoms or a complex spectrum of symptoms dominated by central or peripheral nervous system dysfunction. Many neurological presentations may arise from the same metabolic defect, especially in autosomal-recessive inherited disorders. Motor neuron disease (MND), mainly represented by amyotrophic lateral sclerosis, may also result from various inborn errors of metabolism, some of which may represent potentially treatable conditions, thereby emphasizing the importance of recognizing such diseases. The present review discusses the most important neurometabolic disorders presenting with motor neuron (lower and/or upper) dysfunction as the key clinical and neuropathological feature.