Dysmorphology Assessment of the Newborn

Summary
Introduction
History Checklist
Examination Checklist
Investigations - when to do what?
Communication Strategies with Parents

Summary

a thorough history and examination is required
ancillary investigations may be useful
chromosome and gene tests may be warranted in certain circumstances
parental communication is important
potentially 'offensive' terms should be avoided

Introduction

A dysmorphology assessment of a newborn focuses on aspects of history, examination and investigations that may lead to a syndrome diagnosis. This assessment should be carried out in any child with any of the following

congenital abnormality
growth abnormalities
dysmorphic features

Below are checklists for history and examination with a dysmorphology focus as well as investigations that the paediatrician should consider as part of a dysmorphology work-up.

For many doctors, the discussion of issues relating to syndrome diagnosis and dysmorphism can be difficult, and some suggestions are outlined.

History Checklist

pregnancy history, noting particularly exposure to teratogens, amniotic fluid volume
results of ultrasound and amniocentesis/CVS
fetal movements
maternal illness
delivery history
family history of abnormalities
consanguinity

Examination Checklist

The following focuses on the examination for dysmorphic features in a baby. A thorough examination of all other systems is vital when considering a syndrome diagnosis.

Growth

Birth weight, length and head circumference. Assess whether the baby's growth parameters are in proportion as well as the percentiles

Ectodermal Features

skin - texture and colour, birthmarks, redundancy, defects
hair - scalp hair and body hair: colour and distribution. Note position of anterior and posterior scalp hairline

Skull

shape, symmetry
sutures (over-riding/normal/widely open)
fontanelle size and number

Face

In examining the face, it can be useful to first gain an overall impression of the facial appearance. Sometime, an overall gestalt can be diagnostic (e.g. Down syndrome). If no diagnosis is made, it is then important to divide the face into sections to examine it thoroughly. You may divide the face into the forehead, midface and oral region. It can sometimes help to cover parts of the face with your hand, in order to isolate the section of the face you are assessing.

In assessing the face, it is important to view the face from the front and from the lateral view. The depth or height of structures such as the nasal bridge, the position of the mandible relative to the maxilla and the development of the midface are best assessed by the lateral view.

Overall face shape, symmetry, facial muscle movement
Forehead region
- forehead shape - (broad/bitemporal narrowing/tall)
- eyes
  - palpebral fissure length (short/long)
  - palpebral fissure slant (up/down)
  - epicanthic folds - a fold of skin which arcs from below the eye into the upper lid
  - eye spacing (use a rough guide of 1:1:1 for the ratio of left palpebral fissure length: inner canthal distance: right palpebral fissure length)
  - palpebral fissure shape
  - iris colour
  - pupil shape
  - retina
  - globe position (assessed from lateral view: protuberant vs deep set globes)
Midface region
- nose
  divide the nose into 3 sections from the lateral view from superior to inferior into the nasal root, bridge and tip.
  - root
  - bridge (depressed/prominent/broad)
  - tip
  - columella (the vertical ridge separating the nostrils)
  - nostrils - patency, position (anteverted nostrils often reflect a short nose)
- ears
  - ear position should be assessed relative to the face, from the lateral view
  - ear rotation is normally 15 degrees posterior to the vertical plane of the head
  - ear shape and structure
Oral region
- mouth size and shape
- lip shape, thickness
- gum thickness
- philtrum definition and length
- jaw position (prognathia/micrognathia)
- palate shape
- oral cavity - natal teeth/frenulum/tongue size and morphology

Hands and Feet

overall shape and size of hand and foot
digit number
digit shape (e.g. clinodactyly) and length
webbing between digits
palmar, plantar and digit creases
nail morphology

Joints and Skeleton

contractures
limb shortening
joint range of movement
soft tissue webbing across joints (pterygium)
sternum length and shape (pectus carinatum/excavatum)
shape of thoracic cage
spine length, straight/curved
neck length, webbing

Genitalia and Anus

phallus size, morphology
development of scrotum and palpation of testes
development of labia
position of anus relative to genitalia, patency of anus

Examination of other family members (siblings and parents) may be crucial to determining whether any dysmorphic features noted are familial or syndromic.

Investigations - when to do what?

Tests in the syndrome work-up

renal ultrasound, echocardiogram and cranial ultrasound may be indicated when a syndrome is suspected. In particular, midline abnormalities tend to cluster together, so, for example, an echo may be indicated when there is a cleft palate and dysmorphic features
eye examinations are useful for clues to make a syndrome diagnosis
skeletal radiographs - are indicated when there is disproportionate short stature, or other abnormalities in the skeletal system. X rays may be useful in diagnosing a skeletal dysplasia, which is a disorder caused by a primary abnormality of bone growth/development, or to assist in diagnosing a dysmorphic syndrome which can have skeletal abnormalities associated with it

A genetic skeletal survey includes

AP and lateral X rays of the skull

AP and lateral pelvis and spine (cervical to sacrum)

AP of one arm

AP both hands

AP of one leg and AP of both feet

In a neonate, it may be sufficient to obtain a "baby-gram" (X-ray of the baby) and a separate X ray of the hands and feet.

Chromosome, fluorescent in-situ hybridisation (FISH), single gene and biochemical tests

Blood chromosomes are indicated

when there are multiple congenital abnormalities +/- dysmorphic features
when there is one congenital abnormality in the presence of dysmorphic features and/ or growth retardation

Chromosome abnormalities are more likely when there are abnormalities of growth, most commonly growth retardation and microcephaly, in association with dysmorphic features and congenital abnormalities.

Note that a normal chromosome analysis does not exclude a single gene mutation or a micro deletion syndrome. Also, a normal antenatal chromosome analysis does not completely exclude a chromosome abnormality, as the resolution of chromosome banding may be greater on a postnatal sample than samples from chorion villus sampling or amniocentesis. If a chromosome abnormality is strongly suspected, it is indicated to repeat chromosomes in the postnatal period.

A chromosome test takes a minimum of 5 days and the time taken to obtain a result depends on the growth of cells in culture.

If an infant has been transfused, there is a small risk that there may be circulating lymphocytes from the blood donor, which may lead to an ambiguous result. Most laboratories recommend delaying a karyotype until one week following a transfusion.

FISH for Trisomies 13/18/21 are used to expedite diagnosis when Trisomy of a specific chromosome is suspected. A result is usually available within 48 hours. FISH for submicroscopic deletion syndromes are tests using a probe that detects small chromosome deletions not visible on routine chromosome analysis.

22q FISH should be considered in babies with heart defects, particularly those with cleft palate and dysmorphic features. The commonest cardiac defects seen are conotruncal heart defects and VSD
7q FISH (Williams' syndrome) should be considered in babies with supravalvular aortic stenosis and/or hypercalcaemia

Fragile X testing is rarely indicated in the neonatal period in the absence of a family history.

Single gene tests may be indicated, depending on the syndrome being considered. Such tests usually require liaison with the clinical geneticist.

Biochemical tests may be indicated, such as 7-dehdrocholesterol assays if considering Smith-Lemli-Opitz as a diagnosis.

Communication Strategies with Parents

It can be awkward to raise a concern that a child is dysmorphic. However, it is important to communicate concerns to the family in order to assist them in understanding the reasons behind investigations, examinations of other family members, and referrals to genetics. Withholding concerns regarding dysmorphism can be bewildering and frightening to parents.

One useful tactic is to ask the parents whom the child resembles in the family. The family may then disclose their concerns regarding the child's appearance, and this can then be a topic for careful discussion. Geneticists often explain that the reason for examining the baby's appearance is to look for clues as to the cause of the problem(s) seen in the baby. Feedback from families suggests that it is best to avoid terms such as dysmorphic, and to use in preference terms such as "distinctive facial features". Families report that the terms abnormal or deformed can be offensive, and that an abnormality is better described as a problem or difficulty.

References

Aase, JM. Diagnostic dysmorphology Plenum Medical Book Company, New York, 1990

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