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LETTER TO THE EDITOR
Year : 2017  |  Volume : 12  |  Issue : 1  |  Page : 115-116
 

Mucolipidosis type II secondary to GNPTAB gene deletion from India


1 Department of Pediatric Neurology, Indira Gandhi Institute of Child Health, Bengaluru, Karnataka, India
2 Department of Pediatrics, Indira Gandhi Institute of Child Health, Bengaluru, Karnataka, India
3 Department of Genetics, Indira Gandhi Institute of Child Health, Bengaluru, Karnataka, India

Date of Web Publication4-May-2017

Correspondence Address:
Vykuntaraju K Gowda
#141, 7Th C Main, Hampinagar, Vijayanagar, Bengaluru, Karnataka
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/1817-1745.205656

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How to cite this article:
Gowda VK, Raghavan VV, Bhat M, Benakappa A. Mucolipidosis type II secondary to GNPTAB gene deletion from India. J Pediatr Neurosci 2017;12:115-6

How to cite this URL:
Gowda VK, Raghavan VV, Bhat M, Benakappa A. Mucolipidosis type II secondary to GNPTAB gene deletion from India. J Pediatr Neurosci [serial online] 2017 [cited 2022 Jan 23];12:115-6. Available from: https://www.pediatricneurosciences.com/text.asp?2017/12/1/115/205656




Dear Sir,

Mucolipidosis II (ML II) is a rare autosomal recessive disorder of lysosomal metabolism. It has often been clinically misdiagnosed as mucopolysaccharidosis. ML II is characterized by developmental delay, short stature, coarse facial features, and dysostosis multiplex.[1] We are reporting 9-month-old girl born to a second degree consanguineously married couple presented with developmental delay and noisy breathing. Examination revealed coarse facies, thick eyebrows, hypertelorism, bilateral corneal clouding, pectus excavatum, and kyphosis. There was hepatosplenomegaly but no cherry red spot. On investigations, thyroid function test and urine glycosaminoglycans were normal. Skeletal survey shows kyphosis of dorsal spine. Magnetic resonance imaging brain shows mild cerebral atrophy. Enzyme analysis in plasma shows elevated, alpha-mannosidase12,970 (normal: 20–120)-nmol/h/ml, alpha-fucosidase-6624 (normal: 90–610)-nmol/h/ml, and beta-hexosaminidase-T-23090 (normal: 620–4990) nmol/h/ml. High levels are suggestive of ML II/III. GNPTAB gene testing revealed a homozygotic deletion in exon 19 (c_3503_3504delTC). Based on severe MPS phenotype in early infancy, enzyme assay, and genetic testing, we diagnosed the case as ML II.

ML II is caused by deficiency of N-acetylglucosmine -1-phosphottransferase. This enzyme deficiency can produce two different phenotypes, ML II and ML III (pseudo-Hurler polydystrophy).[2] ML II and III differ in age of onset with ML II being present at birth and ML III starting clinical symptoms between 3 and 5 years of age. ML II causes severe intellectual disability, coarse facial features, skeletal abnormalities, and an early death during first decade. ML III is a late onset with variations in intellectual disability (normal to decreased), skeletal abnormalities which are prominent and these individuals may live for a number of decades. Based on above differences, we considered possibility of ML II in our child.[3]

We excluded MPS based on early infancy presentation and absent of glycosaminoglycans in the urine. We ruled out congenital hypothyroidism based on normal thyroid function tests. We also excluded GM1 gangliosidosis and Sialidosis as child had no startle response, epilepsy, and cherry red spot in the fundus. Cury et al. reported mutation c_3503_3504delTC located in exon 19 was most common mutation (n = 11/24) in ML II and III in Brazil.[4] This mutation from Indian subcontinent is useful for the molecular diagnosis of ML II in India.

ML II should be considered as one of the differential diagnoses in patients presenting in early infancy with MPS phenotype. ML II is differentiated from ML III based on severe and early presentation in former.

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Conflicts of interest

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   References Top

1.
Yang Y, Wu J, Liu H, Chen X, Wang Y, Zhao M, et al. Two homozygous nonsense mutations of GNPTAB gene in two Chinese families with mucolipidosis II alpha/beta using targeted next-generation sequencing. Genomics 2013;102:169-73.  Back to cited text no. 1
    
2.
Aynaci FM, Cakir E, Aynaci O. A case of I-cell disease (mucolipidosis II) presenting with craniosynostosis. Childs Nerv Syst 2002;18:707-11.  Back to cited text no. 2
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3.
Donald F, Farrell. Mucolipidosis II α/β and III α/β: Phenotypic correlations. Biol Biomed Rep 2012;2:328-41.  Back to cited text no. 3
    
4.
Cury GK, Matte U, Artigalás O, Alegra T, Velho RV, Sperb F, et al. Mucolipidosis II and III alpha/beta in Brazil: Analysis of the GNPTAB gene. Gene 2013;524:59-64.  Back to cited text no. 4
    




 

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