Description, Causes and Risk Factors:
Alternative Names: Bird-Headed Dwarfism, Seckel Type, microcephalic primordial dwarfism, nanocephalic dwarfism, Seckel type dwarfism, Seckel type primordial dwarfism, nanocephalic dwarfism.
Seckel syndrome is an extremely rare inherited disorder characterized by low birth weight, dwarfism, a very small head, mental retardation, and unusual characteristic facial features, including a "beak-like" protrusion of the nose, large eyes, a narrow face, low ears, and an unusually small jaw. It occurs in 1:10,000 children without sex predominance.
In 2000, a gene for a Seckel syndrome was mapped to human chromosome 3q22.1-q24 (SCKL1) by homozygosity mapping in two families from the same village, with a genetic interval of 12 cM defined by loci D3S1316 and D3S3710. This gene has subsequently been identified as ATR (ataxia-telangiectasia and RAD-3 related protein) in the same families. The ATR mutation (A2102G in exon 9) is translationally silent but affects splicing efficiency, resulting in low levels of ATR in affected individuals. ATR is central player in a signaling response to DNA damage that functions in concern with ATM. Unlike ATM, current evidence suggests that ATR responds to regions of single stranded DNA generated at the stalled replication forks and bulky lesion and that ATR is essential, not only for development but also for somatic cell growth. The role of the ATR gene in DNA-damage response can explain the chromosomal instability in some Seckel patients. Cell derived from ATR-Seckel patients demonstrated impaired phosphorylation of a range of ATR-dependant substrates following exposure to UV-radiation of hydroxyurea, but a normal ATM-dependant response to ionising radiation.
Another loci has been mapped in 2001 and in 2003 to chromosome 18p11.31-q11.2 (SCKL2) in one inbred Iraqi family and to chromosome 14q23 (SCKL3) in 13 Turkish families. This linkage results support the view that Seckel syndrome is a genetically heterogeneous condition and these genes remain to be identified. Analysis of Seckel syndrome cell lines suggest that defects in ATR signaling are common, although the defective gene is not always ATR.
Seckel syndrome displays an autosomal-recessive pattern of inheritance. This means that both parents of a child with the disorder carry a copy of the Seckel gene, but the parents appear entirely normal. When both parents carry a copy of the Seckel gene, their children face a one in four chance of developing the disorder.
Symptoms may include the following:
Extremely small proportionate stature (dwarfism).
Very small head (microcephaly).
"Beak-like" protrusion of the nose.
Unusually small jaw (micrognathia).
Mental retardation, often severe (IQ less than 50).
Very small at birth (average birth weight is 1,540 g or about 3.3 pounds).
It can be challenging for physicians to differentiate true Seckel syndrome from other similar dwarfisms.Most of the primary diagnostic features of Seckel syndrome, which include severe intrauterine growth restriction, a small head, characteristic "bird-like" facies, and mental retardation, are well suited for prenatal sonographic diagnosis.
The use of ultrasound examination to evaluate fetal growth and the careful evaluation of the fetal face and cranial anatomy has proven effective at detecting Seckel syndrome.
X-ray features include retarded bone age, frequent hip dysplasia and dislocation of the head of the radius.
There is no cure for Seckel syndrome. Certain medications may be prescribed to address other symptoms associated with the disorder.
Hematological abnormalities have been reported in a few cases with Seckel syndrome, including anemia, pancytopenia, and acute myeloid leukemia, and medical treatment is proposed depending on the symptoms. Mental retardation is usually severe and family should be helped for social problems.
Children affected with Seckel syndrome can live for an extended period of time, although they are often faced with profound mental and physical deficits.
NOTE: The above information is educational purpose. The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition.
DISCLAIMER: This information should not substitute for seeking responsible, professional medical care.
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