10.3 The dysmorphic child
Dysmorphic, which literally means ‘abnormal form’, refers to an unusual appearance, usually of the face. A dysmorphic child may have an underlying diagnosis that could have implications for the health not only of the child but also of other family members if the condition is inherited. With the advent of new genetic testing options such as array comparative genomic hybridization (‘microarray’) and an upsurge in commercially available tests for single-gene disorders, our understanding of the genetic basis underlying the dysmorphic child is improving all the time. The dysmorphic child may present as a neonate with one or more birth defects (e.g. a missing hand), or later with developmental delay or intellectual disability, failure to thrive or obesity, short or tall stature, a behavioural disturbance or a metabolic problem.
Birth defects can be classified as deformations, disruptions, dysplasias or malformations (see Chapter 10.1). It is important to distinguish between abnormalities and minor variants that are common in the general population. These can, however, appear in syndromes. For example, a unilateral single transverse palmar crease is seen in 4% of normal people but is more common in Down syndrome. Some physical traits, such as an unusually shaped nose, are a harmless family variant but again could be part of an undiagnosed syndrome in the family.
Making an overall diagnosis relies on recognizing a pattern of problems. The types of pattern include:
• Syndrome. This is from the Greek ‘running together’ and refers to a cluster of physical and other features occurring in a consistent pattern, with an implied common specific cause that may be unknown. The word syndrome is often used loosely to describe any of the other diagnostic patterns described below.
• Association. This is a group of physical features that tends to occur together but the link is not consistent enough to allow the term syndrome to be used. An example is the VATER association (see below). The distinction between a syndrome and an association may be artificial and, increasingly, associations are being redefined as syndromes as their genetic basis is identified. For example, in 2004 CHARGE association (Coloboma, Heart defects, Atresia choanae, Retardation of growth and development, Genital and Ear anomalies) was identified as being due to mutations in the CHD7 gene on chromosome 8; with this, CHARGE association became CHARGE syndrome.
• Sequence. This refers to a group of abnormalities caused by a cascade of events beginning with one malformation. An example is the Potter sequence, which can result from any cause of severe oligohydramnios. For example, renal agenesis results in no fetal urine, leading to severe oligohydramnios, with the consequence of lung hypoplasia and intrauterine constraint, causing limb deformities, such as talipes, and a compressed facial appearance.
• Developmental field defect. This refers to a group of malformations caused by a harmful influence in a particular region of the embryo. Abnormalities of blood flow are thought to underlie many of these. An example is hemifacial microsomia with unilateral facial hypoplasia and ear anomalies relating to an abnormality in development of first and second branchial arch structures.
Why is it necessary to recognize an underlying diagnosis? Some important reasons are:
• avoiding unnecessary investigations
• providing information about prognosis for doctors and family
• recognizing and treating complications that need to be looked for prospectively
• determining the pattern of inheritance and recurrence risk
• enabling support from other families. Individual syndromes are rare and parents become the experts in day-to-day management of the child and can share this with other families.
Are there any pitfalls in making a diagnosis? Some areas for consideration are:
• The diagnosis must be correct: the diagnosis may be based on clinical assessment alone with no confirmatory tests available; diagnosis must not be undertaken lightly as it can be difficult to remove or alter a diagnosis once it has been made, with harmful consequences for the child and family.
• Parents do not wish their child to be labelled, especially if the child is young and they do not yet perceive any problems themselves.
• Syndromes are individually rare but collectively common.
• Accurate syndrome diagnosis is important to give information about prognosis, associated problems, recurrence risk and support groups for families.
• Diagnoses are made by thorough clinical assessment followed by use of aids such as computerized syndrome databases.
• Even an experienced clinical geneticist may not make a syndrome diagnosis in a child with dysmorphic features.
• It is better to make no syndrome diagnosis than to make an incorrect diagnosis.
How to assess the dysmorphic child
Instant recognition
A ‘waiting room diagnosis’ based on the facial ‘gestalt’ might be made if the doctor has seen a person with the particular syndrome before, just as most people are able to recognize whether a person in the street has Down syndrome. Often, however, the diagnosis is not apparent initially, and the following approach is recommended.
History
Special points in the medical history include:
Growth and development, behaviour, sleep patterns.
Family history – draw a three-generation family tree noting miscarriages, stillbirths and deaths of siblings, any history of intellectual disability, congenital abnormalities or consanguinity (i.e. are the parents related?), and enquire about other family members with the same features.
Examination
Observe the child before undressing or disturbing her or him. On the other hand, the examination is not complete until the child has been fully undressed. Especially note:
• height, weight, head circumference and shape, body proportions (e.g. height to arm span ratio, upper and lower body segment length) and any asymmetry
• always plot measurements on standard normal charts. Charts are available for many different body parts (e.g. hand measurements, foot and ear length). Special charts are available for certain disorders (e.g. Down syndrome) and various bone dysplasias (e.g. achondroplasia)
• facial features (Fig. 10.3.1) – careful assessment of facial anatomy often provides clues to the diagnosis
• chest shape and spinal curvature
• proportions of the limbs, muscle bulk and tone, joint contractures and mobility
• structure of hands and feet (shape, length, number of digits, dermal ridges, nails)
• skin pigmentary or vascular markings
• any birth defects? (e.g. cleft palate)
• auscultate the chest for any cardiac murmurs
Fig. 10.3.1 Normal human face: list of common terms used in dysmorphology. (A) 1, Supraorbital ridge; 2, outer canthus; 3, inner canthus; 4, palpebral fissure (line from inner canthus to outer canthus); 5, nasal root; 6, nasal bridge; 7, nasal tip; 8, naris/nares; 9, columella; 10, philtrum; 11, nasolabial fold; 12, upper vermillion border of lip. (B) Lateral view: 13, line indicating normal ear height – the superior attachment of the pinna should lie above an imaginary line drawn through bo;;th inner canthi and running posteriorly; ‘low-set’ ears are below this line; 14, lobule; 15, helix; 16, tragus; 17, antihelix.
A photograph (with parental consent) is useful for:
When examining the family of a child with unusual facial features:
Putting it all together
• Check textbooks of syndromes (e.g. Smith’s Recognizable Patterns of Human Malformation) by trying to match the most important dysmorphic features and comparing the photographs with those of the patient.
• It’s not easy! A skilled dysmorphologist makes a syndrome diagnosis in a dysmorphic child in about 30% of cases referred by an experienced paediatrician. If an overall diagnosis is not made, the recognized problems must still be managed.
• Review in 3–5 years’ time is often valuable and may allow a diagnosis to be made as the features of the syndrome evolve over time and new information or laboratory techniques become available.
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