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Microcephalic Osteodysplastic Primordial Dwarfism 2
What is Microcephalic Osteodysplastic Primordial Dwarfism 2?
It is a rare genetic syndrome. Dwarfism, an exceptionally short stature, skeletal abnormalities and a small head characterize the syndrome. These symptoms begin before birth.
This syndrome is also known as:
Majewski osteodysplastic primordial dwarfism Microcephalic osteodysplastic primordial dwarfism type II Mopd Ii Osteodysplastic Primordial Dwarfism, Type II
What gene changes cause Microcephalic Osteodysplastic Primordial Dwarfism 2?
Changes in the PCNT gene are responsible for causing the syndrome.
The syndrome is inherited in an autosomal recessive pattern.
What are the main symptoms of Microcephalic Osteodysplastic Primordial Dwarfism 2?
The main symptoms of the syndrome are dwarfism, a very short stature, and a very small head. This delayed and restricted growth can usually be identified before birth. This also leads to the development of a smaller brain size although this does not affect intellectual development.
Skeletal abnormalities associated with the syndrome include scoliosis (curving of the spine), hip dysplasia (affecting the joints in the hip), shorter wrist bones and a thinking of the bones found in the arms and legs.
Unique facial features of the syndrome include a prominent nose, full cheeks, a long midface, a small jaw, small teeth and farsightedness. Some individuals also develop lighter or darker skin coloring.
Blood vessel abnormalities are common with the syndrome. This can include a bulge in one of the blood vessels found at the center of the brain. Known as aneurysms these can be dangerous if they burst and cause bleeding within the brain. Some individuals are affected by Moyamoya disease where the arteries found at the base of the brain are narrower than they should be, this in turn can restrict blood flow. While treatable these symptoms can increase the risk of stroke in affected individuals.
Possible clinical traits/features:
Upslanted palpebral fissure, Sparse scalp hair, Radial bowing, Ulnar bowing, Slender long bone, Tracheal stenosis, Scoliosis, Tibial bowing, Reduced number of teeth, Moyamoya phenomenon, Pseudoepiphyses of the metacarpals, Truncal obesity, Recurrent respiratory infections, Type II diabetes mellitus, Proximal femoral epiphysiolysis, Thin clavicles, Microcephaly, Disproportionate short stature, Intrauterine growth retardation, Intellectual disability, Abnormality of female external genitalia, Straight clavicles, Sloping forehead, Long clavicles, Low-set, posteriorly rotated ears, Micromelia, Microdontia, Micrognathia, Microtia, Narrow pelvis bone, Narrow chest, Limited elbow extension, Joint hypermobility, Laryngomalacia, Ivory epiphyses, Full cheeks, Short distal phalanx of finger, Hypermetropia, Prominent nasal bridge, High pitched voice, Cognitive impairment, Global developmental delay, Postnatal growth retardation, Hypoplastic iliac wing, Underdeveloped nasal alae, Hypoplastic scapulae, Short middle phalanx
How does someone get tested for Microcephalic Osteodysplastic Primordial Dwarfism 2?
The initial testing for Microcephalic Osteodysplastic Primordial Dwarfism 2 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.
Medical information on Microcephalic Osteodysplastic Primordial Dwarfism 2
This form of microcephalic primordial dwarfism somewhat resembles Seckel syndrome, but there are important clinical and radiological differences. There is severe pre- and post-natal growth retardation, microcephaly, a small forehead, a prominent nose, micrognathia and mental retardation. Limb shortening is mesomelic. Radiographs show short 1st metacarpals, short middle phalanges, short, curved, forearm bones, a V-shaped flare of the distal femoral metaphyses, coxa vara with a fragmented and flattened proximal femoral epiphysis, triangular distal femoral epiphyses, a high and narrow pelvis and pseudoepiphyses of the hands. The inheritance is uncertain, although one pair of possibly affected sibs and parental consanguinity have been reported (Verloes et al., 1987; Shebib et al., 1991). Herman et al., (1991) and Al Gazali et al., (1995) reported further cases and provide good reviews of the radiological features.
Masuno et al., (1995) reported a case with some features of the condition. However mesomelic shortening was seen in the legs but not in the arms, the pelvis was broad and not narrow, and there was no evidence of coxa vara or cupping of the distal femoral metaphyses.
Lin et al., (1995) reported two brothers with the radiological features of the condition and microdontia. They pointed out that the cases reported by Majewski et al., (1982) and Shebib et al., (1991) had similar tooth abnormalities.
Spranger et al., (1996) reported a case with some unusual features. These included bilateral knee dislocation, breathing difficulties due to a microlarynx and misplaced upper lobe bronchus, severe undermineralisation of the skull and partial agenesis of the corpus callosum. Further cases were reported by Halder et al., (1998) and Majewski and Goecke (1998). The case reported by Halder et al., (1998) had normal intelligence but delayed central nervous system myelination with mild dilatation of the lateral ventricles at four years. The case reported by Ozawa et al., (2005) had pachygyria.
Faivre et al., (2002) studied two consanguineous families and could not find linkage to the Seckel loci on 3q or 18p.
Nishimura et al (2003) reported a case associated with cafe-au-lait spots and moyamoya disease. Young et al., (2004), reported another child with this combination. There were in addition hypopigmented patches. The patient reported by Kanna et al., (2004) had cafe-au-lait spots and cutis marmorata. Four patients reported by Bober et al., (2010) had neurovascular complications. One had coronary artery abnormalities.
There is an excellent, comprehensive review of the condition by Hall et al., (2004). In a follow-up of cases, these authors note the occurrence of CNS haemorrhage, strokes and moyamoya disease. This was again commented on by Brancati et al., (2005) who reported a patient with a stroke at 2 -3 years of age. Dieks et al., (2014) reported a case with intracranial aneurysms.
The condition has now been mapped to 21q22 and mutations have been found in pericentrin (PCNT) - Rauch et al., (2008). An absence of PCNT results in disorganized mitotic spindles and missegregation of chromosomes (Rauch et al., 2008).
Some cases, previously diagnosed as having Seckel, have been reclassified as having Majewski osteodysplastic primordial dwarfism (Piane et al., 2009, Willems et al., 2010). Both can be caused by PCNT mutations. In the Willems et al., (2010) report, all cases diagnosed clinically thith MOPD II had mutations whereas 5 out of 16 of those clinically said to have Seckel had mutations.
* This information is courtesy of the L M D.
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