Dysmorphology Flashcards
What is the definition of morphology?
the scientific study of the structure and form of either animals and plants or words and phrases
this usually involves features in the face
At what stage of life is diagnosis of a dysmorphic condition usually easiest and why?
diagnosis is easier in children than in babies and adults
this is because features change with age
What % of births are affected by a congenital malformation?
2-3% of births
single malformations are often isolated events
What things suggest that a congenital malformation is likely to be genetic?
- if there are multiple malformations
- dysmorphic
- family history of similar problems
Why is it important to detect dysmorphology?
it assists in making a diagnosis
this diagnosis guides prognosis, management and recurrence risk
What type of abnormality is present in DiGeorge syndrome?
22q11.2 deletion
deletion of a small part of chromosome 22 near the middle of the chromosome at a location known as q11.2
Approximately how many births are affected by a 22q11.2 deletion?
What symptoms are present in most patients with this deletion?
affects around 1 in 5,000 births
symptoms are very variable but most patients have:
- hypocalcaemia
- seizures
- immune deficiency
- renal malformation
What symptoms are present in some patients with DiGeorge syndrome, but not all?
- 70% have learning difficulties
- 15% have cleft palate
- 32% have velopharyngeal insufficiency
- 75% congenital heart defects
What is achondroplasia?
Around how many births are affected by this condition?
a bone growth disorder that causes disproportionate dwarfism
it affects around 1 in 20,000 people
What are the typical features visible in a person with achondroplasia?
- rhizomelic limb shortening
- short stature
- foramen magnum compression/hydrocephaly
What is meant by “rhizomelic” limb shortening?
Rhizomelia refers to a disproportion of the length of the proximal limb
What is meant by a foramen magnum compression?
What can this lead to?
the foramen magnum is a hole at the base of the skull, through which brainstem and spinal cord pass
compression leads to a “kink” in the brainstem, which can cause sleep apnea
what often causes achondroplasia?
it is autosomal dominant and is usually caused by a new mutation
risk increases with paternal age
What is meant by Beckwith-Wiedemann syndrome?
it is an overgrowth syndrome usually present at birth
it is characterised by an increased risk of childhood cancer and certain congenital features
How many births are affected by Beckwith-Wiedemann syndrome?
What is there an increased risk of in this condition?
1 in 10,000
there is an increased risk of Wilms tumour (nephroblastoma - a rare kidney cancer)
What features are seen in someone with Beckwith-Wiedemann syndrome?
- large tongue
- ear pits/creases
- exomphalos
- hemihypertrophy
- neonatal hypoglycaemia
What is meant by exomphalos?
there is a weakness in the abdominal wall where it joins to the umbilical cord
this allows abdominal contents (mainly bowel & liver) to protrude outside of the abdominal cavity
What is meant by ‘hemihypertrophy’?
a condition in which one side of the body (or part of it) is larger than the other to an extent considered greater than the normal variation
Approximately how many births are affected by Down’s syndrome?
1 in 800
What are the typical visible features associated with Down’s syndrome?
- single palmar crease
- cataracts
- hypotonia in neonates
What other diseases/conditions is Down’s syndrome associated with?
- congenital heart disease
- hypothyroidism
- hearing impairments
- leukaemia
- alzheimer’s disease
What is meant by hypotonia in Down’s syndrome?
the presence of decreased muscle tone
What is meant by a single palmar crease in Down’s syndrome?
What is meant by atlanto-axial instability in Down’s syndrome?
excessive movement at the junction between the atlas (C1) and axis (C2) as a result of either a bony or ligamentous abnormality
