Zellweger syndrome, also called cerebrohepatorenal syndrome is a rare, congenital disorder (present at birth), characterized by the reduction or absence of peroxisomes in the cells of the liver, kidneys, and brain. It is one of a family of disorders called leukodystrophies.
As a result of impaired peroxisome function, an individual’s tissues and cells can accumulate very long chain fatty acids (VLCFA) and branched chain fatty acids (BCFA) that are normally degraded in peroxisomes. The accumulation of these lipids can impair the normal function of multiple organ systems, as discussed below. In addition, these individuals can show deficient levels of plasmalogens, ether-phospholipids that are especially important for brain and lung function
Cri du chat syndrome is a group of symptoms that result from deletion on chromosome number 5. The syndrome’s name is based on the infant’s cry, which is high-pitched and sounds like a cat.
It was first described by Jérôme Lejeune in 1963.
Approximately 90% of cases results from a sporadic, or randomly-occurring, de novo deletion. The remaining 10-15% are due to unequal segregation of a parental balanced translocation where the 5p monosomy is often accompanied by a trisomic portion of the genome. These individuals may have more severe disease than those with isolated monosomy of 5p.
Loss of a small region in band 5p15.2 (cri du chat critical region) correlates with all the clinical features of the syndrome with the exception of the catlike cry, which maps to band 5p15.3 (catlike critical region). The results suggest that 2 noncontiguous critical regions contain genes involved in this condition’s etiology. Two genes in these regions, Semaphorine F (SEMA5A) and delta catenin (CTNND2), are potentially involved in cerebral development. The deletion of the telomerase reverse transcriptase (hTERT) gene localized in 5p15.33 may contribute to the phenotypic changes in cri du chat syndrome as well.
- Cry that is high-pitched and sounds like a cat
- Downward slant to the eyes
- Low birth weight and slow growth
- Low-set or abnormally shaped ears
- Mental retardation
- Partial webbing or fusing of fingers or toes
- Single line in the palm of the hand (simian crease)
- Skin tags just in front of the ear
- Slow or incomplete development of motor skills
- Small head (microcephaly)
- Small jaw (micrognathia)
- Wide-set eyes
In addition to symptoms, the physical examination may show:
- Inguinal hernia
- Diastasis recti (separated abdominal muscles)
- Low muscle tone
- Epicanthal folds, an extra fold of skin over the inner corner of the eye
- Incompletely or abnormally folded external ears
Genetic tests show the deletion on chromosome 5.
Skull x-ray may reveal an abnormal angle to the base of the skull.
There is a specific way to label a karyotype. A human has 23 sets of chromosomes, and thus, a total of 46 chromosomes. Twenty-two of these pairs are autosomal chromosomes, and the last pair is comprised of the sex chromosomes, which don’t have to be identical. A karyotype is labeled in the following fashion: number of chromosomes, sex chromosomes (by listing XX for female, or XY for male), any genetic malfunctions. For example, a normal male would be 46, XY, and a normal female would be 46, XX.
Labelling the chromosome using international cytogenetic nomenclature
inversion and transloation examples shown below by arrows
Carpenter syndrome, also called acrocephalopolysyndactyly type II, is an extremely rare autosomal recessive congenital disorder characterized by craniofacial malformations, obesity, and syndactyly.
Apert syndrome is a form of acrocephalosyndactyly, a congenital disorder characterized by malformations of the skull, face, hands and feet. It is classified as a branchial arch syndrome, affecting the first branchial (or pharyngeal) arch, the precursor of the maxilla and mandible
Genetic counselling: The process by which patients or relatives at risk for a disorder that may be hereditary are advised of
- The consequences of the disorder
- The probability of developing or transmitting the disorder
- The ways in which this may be prevented, avoided or ameliorated
It involves elements from several disciplines:
- psychotherapy – supportive counselling of a social field
- diagnositics – clincial medincal testing of the inherited disease
- mathematics – complex mathematical, statictical process involving the estimationo risk
The core elements of genetic counselling practice
- Diagnostic and clinical aspects
- Documentation of family and pedigree information
- Recognition of ineritance patterns and risk estimation
- Communication and empathy with those seen
- Infomation on available options and further measures
- Support in decision-making and for decisions made
Considerations when interviewing:
- Did the family themselves initiate the request for genetic counselling or did someone else?
- Is there an unspoken or an exaggerated fear of the disorder?
- Do feelings of guilt or hostility exist between parents?
- Is the rest of the family supportive or are there tensions between the generations?
- Is an affected child valued, loved, or regarded as a burden?
Note: The answers to most of these questions may be obtained by an astute clincian without the need for direcr questioning.
Symbols used in drawing of a pedigree
A nuchal cord occurs when the umbilical cord becomes wrapped around the fetal neck 360 degrees.
There are two types:
- A “Type A” nuchal cord is wrapped around the neck 360 degrees.
- A “Type B” pattern is described as a hitch which cannot be undone and ends up as a true knot
- If the cord is loose, it can easily be slipped over the infant’s head. The infant can be delivered normally and placed on maternal abdomen as desired.
- If the cord is too tight to go over the infant’s head, the provider may be able to slip it over the infant’s shoulders and deliver the body through the cord. The cord can then be unwrapped from around the baby after birth.
- If the cord is too tight to slip back over the shoulders, one may use the somersault maneuver to allow the body to be delivered.
- The birth attendant may also choose to clamp and cut the umbilical cord to allow for vaginal delivery if other methods of nuchal cord management are not feasible.