Flashcards in Clinical Aspects of Learning Disorders Deck (48):
About what % of early miscarriages have abnormalities due to genetic disease?
About 50% of 1st trimester miscarriages.
About what % of newborn infants have a major congenital abnormality?
About what % of childhood deafness, blindness and severe mental retardation is caused by genetic disorders?
About what % of adult chronic disease is caused by genetic abnormalities?
What is the role of a clinical geneticist?
- Establish a diagnosis -history, examination, investigations
- Risk assessment
- Discussion of options
- Counselling of other family members
- Long-term contact and support
What referral indications might be received in the genetics clinic?
- Infant deaths, still-births and miscarriages
- Mental/physical handicap
- Congenital abnormalities
- Maternal medical conditions e.g. epilepsy, diabetes/medication
- Neural tube defects
- Family history of known genetic conditions
- Family history of cancer
How can learning disorders be defined using IQ?
Learning disorders can be defined based on IQ. Typically an IQ less than 70 will be defined as a learning disorder.
Mild = 50-55 to 70
Moderate = 35-40 to 50-55
Severe = 20-25 to 35-40
Profound = less than 20-25
Define Mild learning disorder.
Mild = IQ of 50-55 to 70
Define Moderate learning disorder.
Moderate = IQ of 35-40 to 50-55
Define Severe learning disorder.
Severe = IQ 20-25 to 35-40
Define Profound learning disorder.
Profound = IQ less than 20-25
Other than based on IQ scores, how can learning disorders be defined?
Learning disorders can also be defined on a functional basis. This is based on dysfunction or impairment in more than 2 areas of communication, self-care, home living, social/interpersonal skills, use of community resources, self direction, functional academic skills, work, leisure, health and safety.
What are the most common causes of mild mental retardation?
Down syndrome, Fragile X and other chromosomal abnormalities.
What are the most common causes of severe mental retardation?
Chromosomal abnormalities (including Down), Fragile X, CNS, environmental/prematurity, malformation/syndrome, unknown
What is clinical dysmorphology?
A branch of clinical genetics concerned with the diagnosis and the interpretation of structural defects. There are 3 main types of structural defects known as deformations, disruptions and malformations.
What are the 3 main types of structural defects in clinical dysmorphology?
There are 3 main types of structural defects known as deformations, disruptions and malformations.
What is a deformation in terms of dysmorphology?
A deformation is caused by a mechanical force such as excessive moulding. This often resolves when the mechanical force is removed.
What is a disruption in terms of dysmorphology?
A disruption is the breakdown of normal development such as amniotic bands which restrict the supply of blood to the digits and result in amputation.
What is a malformation in terms of dysmorphology?
A malformation is an intrinsic developmental defect. E.g. cleft lip and palate.
What does the word syndrome mean?
A greek word meaning 'things that run together'.
What is the definition of a syndrome?
A syndrome can be defined as a non-random association of multiple malformations or alterations in body form that are pathogenetically related. Over 4000 syndromes listed on the Winter-Baraitser Dysmorphology Database.
Why does it help to make a diagnosis if they have a syndrome?
- For parents it helps to have a name for a condition in order to explain to others what is wrong, to answer whether or not an individual has been responsible for the condition (or passed it on to their offspring) and also to get extra help.
- Once the condition is known we can give information regarding the associated problems, prognosis, inheritance and treatments. In addition, once you have a diagnosis it is often that you do not require further investigations to come up with a further diagnosis.
Describe what occurs in a dysmorphology consultation.
- First look at history including the pregnancy, birth, development and medical problems.
- Look at the family history to see if there are other individuals involved with the same condition in the family and if there is any consanguinity.
- Physical examination.
- Examine parents and siblings if necessary. Some features may be familial.
- Also important if you are seeing older children or adults to try and review some younger photos as it is possible in some conditions that the characteristic appearances are only present at certain ages.
What is meant by diagnosis by Gestalt?
This is diagnosis by immediate pattern recognition.
What anatomical landmarks in the face can we use to define dysmorphology?
- Facial asymmetry
- Coarse facial features
- Mid-face hypoplasia (excluding malar region)
What anatomical landmarks of the ear can we use to define dysmorphology?
- Ear tags
- Skin pits
- Absence of lobes
- lop ears
- crumpled ears
What anatomical landmarks of the eyes can we use to define dysmorphology?
- Spacing of the eyes (hypo or hyper telorism)
- Sloping of the eyes
- Epicanthic folds
- Coliboma (defect in the iris)
What anatomical landmarks of the eyes can we use to define dysmorphology?
- can describe the anatomy including bridge, tip, nostril and nasal septum etc. and can describe abnormalities of these.
What anatomical landmarks around the mouth can we use to define dysmorphology?
- philtrum features
- Upper lip
e.g. thin upper lip and smooth philtrum seen in fetal alcohol syndrome.
What disorders of skin pigmentation may be seen?
How can we define pathologies based on height?
We first look at whether the short stature is normal or abnormal. If it is abnormal then we will look to see if it is pathologic. If it is pathologic then we need to define whether it is proportionate or disproportionate. If it is an abnormality of the skeleton which is usually disproportionate it is known as skeletal dysplasia.
For example, individuals may have short limbs or a short trunk.
Describe what kind of limb shortening may be seen in skeletal dysplasia.
- Shortening of the proximal limb is known as Rhizomelia.
- Shortening of the distal limb is known as Mesomelia.
What is Rhizomelia?
Shortening of the proximal limb in skeletal dysplasia is known as Rhizomelia.
What is Mesomelia?
Shortening of the distal limb in skeletal dysplasia is known as Mesomelia.
What is Acromelia?
Shortening of the digits in skeletal dysplasia is known as Acromelia.
What is polydactyly?
What is syndactyly?
What is clinodactyly?
In curving of the little finger
What is talipes?
Talipes is a condition that can affect one or both of a baby's feet from birth. In most cases, the front half of the foot turns inwards and downwards. This is called congenital talipes equinovarus (CTE). It is also known as club foot.
How do we decide a child is dysmorphic?
Everybody is dysmorphic. Subtle dysmorphic features in themselves don't make a diagnosis, it is the combination of these plus other clues in history. Deciding a child is dysmorphic or not can be difficult (remember to look at parents). Sometimes a parent has the the syndrome.
Describe the features of Kabuki Syndrome.
- Developmental delay
- Long palpebral fissures
- Everted lateral lower lid
- Arched eyebrows with sparse lateral 1/3
- Broad nasal tip
- Large ears, prominent ear lobes
- High palate
- Lip pits
- Fetal finger pads
- Short stature
- Premature thelarche (breast development)
- CHD, renal anomalies
What gene mutation is responsible for Sotos syndrome?
NSD1 gene mutation.
What are the issues with correctly diagnosing syndromes in individuals?
- Syndromes can be extremely variable.
- syndromes may be very rare and possibly unique to a patient or family.
- One syndrome can be caused by different genes (heterogeneity).
- One gene can be the cause of a number of different syndromes. - Additional features can develop with time, follow up may be needed to make diagnosis.
- Genetic tests have limitations.
Why is the identification of dysmorphology important?
- Dysmorphology is important for diagnosis and genetic counselling.
- It is important for research in the identification of different syndromes, identification of genes and chromosomal regions responsible for specific syndromes, and the understanding of specific mechanisms and gene pathways.
What resources may be utilised by the clinical genetics department in order to define dysmorphology and classify syndromes?
- Karyotyping, FISH, telomeres, skin biopsy, DNA testing, CGH microarrays etc.
- Clinical photos
- Other opinions e.g. opthalmology, dental, cardiac
- Databases e.g. Winter-Baraitser
- Books, journals, Pubmed, OMIM
- Discussion with colleagues
- Dysmorphology meetings (national/international)
- Fetal pathology meetings
List some of the genetic databases available to aid diagnosis.
- The Winter-Baraitser Dysmorphology Database
- European Directory of DNA Laboratories
What are the features of a syndrome often termed?