Mucolipidosis II Alpha/beta

What is Mucolipidosis II Alpha/beta?

Mucolipidosis II syndrome is a rare genetic condition that affects multiple parts and systems of the body.

It is also known as I-cell disease, and as a lysosomal storage disorder.

It is a progressive disorder meaning symptoms worsen with time.

Syndrome Synonyms:
I-cell Disease; Icd ICD Ml Ii Alpha/beta ML2 MLII Mucolipidosis Ii; Ml Ii Mucolipidosis type - II Mucolipidosis type II

What gene changes cause Mucolipidosis II Alpha/beta?

Mutations to the GNPTAB gene are responsible for the syndrome. It is inherited in an autosomal recessive pattern.

Autosomal recessive inheritance means an affected individual receives one copy of a mutated gene from each of their parents, giving them two copies of a mutated gene. Parents, who carry only one copy of the gene mutation will not generally show any symptoms, but have a 25% chance of passing the copies of the gene mutations onto each of their children.

The syndrome is a lysosomal storage disease caused by a deficiency of arylsulfatase B (ASB) caused by mutations in the ARSB gene on chromosome 5. The buildup of these molecules in the body tissue triggers the symptoms of the syndrome.

What are the main symptoms of Mucolipidosis II Alpha/beta?

Babies with Mucolipidosis II are usually born small, with a weak cry and noticeably weak muscle tone.

Throughout infancy and childhood they will present with delayed development- physical and motor.
Individuals with Mucolipidosis II often have what is referred to as distinct or coarse facial features.

Skeletal and joint abnormalities are common in individuals with the syndrome. As are hernias, born umbilical and abdominal.

Other health conditions associated with the syndrome include frequent respiratory infections, frequent rear infections often resulting in hearing loss, a hoarse voice due to a stiffening of the vocal cords and excessive growth of the gums.

Possible clinical traits/features:
Autosomal recessive inheritance, Thin skin, Pathologic fracture, Palpebral edema, Ovoid vertebral bodies, Recurrent otitis media, Umbilical hernia, Protuberant abdomen, Severe global developmental delay, Talipes equinovarus, Weight loss, Recurrent respiratory infections, Splenomegaly, Recurrent bronchitis, Thickened calvaria, Short long bone, Death in childhood, Thoracolumbar kyphoscoliosis, Sparse and thin eyebrow, Heart murmur, Varus deformity of humeral neck, Recurrent pneumonia, Wide intermamillary distance, Severe postnatal growth retardation, Progressive alveolar ridge hypertropy, Myelopathy, Long philtrum, Macroglossia, Inguinal hernia, Increased serum beta-hexosaminidase, Increased serum iduronate sulfatase level, Megalocornea, Lack of skin elasticity, Osteopenia, Metaphyseal widening, Neonatal hypotonia, Lower thoracic interpediculate narrowness, Anteverted nares, Narrow forehead, Mucopolysacchariduria, Cardiomegaly, Broad alveolar ridges, Carpal bone hypoplasia, Bullet-shaped phalanges of the hand,

How does someone get tested for Mucolipidosis II Alpha/beta?

The initial testing for Mucolipidosis II Alpha/beta syndrome can begin with facial analysis screening, through the FDNA Telehealth telegenetics platform, which can identify the key markers of the syndrome and outline the need for further testing. A consultation with a genetic counselor and then a geneticist will follow.

Based on this clinical consultation with a geneticist, the different options for genetic testing will be shared and consent will be sought for further testing.

Medican information on Mucolipidosis II Alpha/beta

This condition is characterized clinically by psychomotor retardation, short stature and Hurler-like features. Most cases present before the child's first birthday, with poor weight gain and coarse facial features. Motor development may be more severely affected than cognitive development. Seizures are rare but can occur (Patel et al., 1980). The skin is often thick, tight and hirsute. Joint movements might be limited and fractures have been reported. Corneal clouding is occasionally present. A large liver and spleen occur in about a half of cases, and with time all seem to develop a gibbus.
Beck et al., (1995) provide an excellent review and stress the variability of the condition both within and between families.
Biochemically there is a deficiency of N-acetyl-a-glucosaminylphosphotransferase (GNPTA) in fibroblasts and leukocytes. An initial screen consists of a search for vacuolated lymphocytes or large cytoplasmic inclusions in skin fibroblasts. An I-cell enzyme screen to show increased levels of a number of lysosomal enzymes in serum or the medium surrounding cultured fibroblasts, and a reduced level intracellularly. Carey et al., (1999) discuss prenatal diagnosis by electron microscopy and biochemical analysis of chorionic villi.
Azimi et al., (2003) reported a case with trigonocephaly. The case reported by Unger et al., (2005) presented severe neonatal hyperparathyroidism. It is well possible that epiphyseal stippling - osteoclastic hyperplasia is, in fact, ML-II too (Saul et al., 2005).
A case with extensive Mongolian spots was reported by Su et al., (2010) and hair pigment lightening (blond hair) in a Chinese baby noted at birth, that turned to black at 2 months, by Ma et al., (2011). A ""blueberry muffin"" rash was reported by Ting et al., (2011).
Yang et. al. (2017) described 7 cases from six families with biallelic GNPTAB gene mutations. Clinical characteristics included short stature, multiple joint contracture, developmental delay, flat face, shallow orbits, depressed nasal bridge, prominent mouth, and gingival hypertrophy. X-rays showed bullet-shaped phalanges, proximal pointing of metacarpals, dysplasia/resorption of the lower third of the iliac femoral heads and femoral necks, Clierd’s crook deformity, thoracolumbar kyphosis, beaking of the vertebrae and J-shaped sella turcica.

* This information is courtesy of the L M D.
If you find a mistake or would like to contribute additional information, please email us at: [email protected]

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