Neerja Gupta*, Madhulika Kabra**
Pool officer, Dept of Pediatrics, AIIMS (DM - Medical genetics) *, Additional Professor of Pediatrics, AIIMS.
Email : firstname.lastname@example.org **
Dysmorphology an art in the medical field is primarily a visual specialty. It is the study of disordered development and covers birth defects that are apparent at or before the time of birth and recognizable structural anomalies. The term 'Dysmorphology' coined by Dr. Smith implies study of human congenital defects, and abnormalities of body structure that originate before birth. It is difficult to define abnormal objectively always but objective criteria for dysmorphology are available in literature.
The term dysmorphic is used to describe children whose physical features, particularly facial are not usually found in a child of the same age or ethnic background. Some features are abnormal in all circumstances e.g., pre/mature fusion of the cranial sutures. These are called good diagnostic "handles" as they are not found as normal or familial traits or variations and are only present in small number of conditions in contrast to 2nd, 3rd toe syndactyly or epicanthic folds which may be non-significant familial trait. The recognition of which features are good diagnostic aids comes with experience. There are special terms in conceptualization of the art of dysmorphology like malformation, deformation, disruption, sequence and association.
The term dysmorphic is used to describe children whose physical features, particularly facial are not usually found in a child of the same age or ethnic background.
|Definitions in Dysmorphology|
A malformation/anomaly is a primary defect where there is a basic alteration of structure, usually occurring before 10 weeks of gestation. Example cleft lip, anencephaly or radial agenesis. A malformation could be major which requires surgical intervention e.g., spina bifida / CHD or manor malformation that requires no treatment or can be corrected totally e.g. Polydactyly.
A minor variant is a low frequency (1-5%) congenital feature that can be found in the normal population or as an integral part of a multiple congenital anomaly (MCA) syndrome. Example: simian crease, clinodactyly of the fifth finger, epicanthic fold, small ears and accessory nipple. Some minor variants are also classified as minor anomalies when part of a syndrome or when no one in the family has similar features.
Deformations / Secondary defect are anomalies caused by unusual mechanical pressure on the developing foetus, usually during the last trimester of gestation e.g., club feet, torticollis and plagiocephaly.
Disruption occurs when there is a breakdown of normal tissue either due to mechanical, vascular or infectious causes. Example: amniotic band sequence and Pierre Robin sequence.
Syndrome (Greek word meaning running together): A dysmorphic syndrome is a recognized pattern of two or more anomalies in an individual due to a common cause. Most of them are made up of one or more major anomalies together with a variable number of minor anomalies. Rarely, any one of these features is diagnostic; instead the entire constellation of defects must be taken into consideration to define the diagnosis.
Recognized dysmorphic syndromes now number in thousands and more seem to be added every month. Example: Marfan syndrome, Apert syndrome.
Association is a non-random occurrence of the same multiple anomalies for which no consistent cause can be established. The core anomalies usually consist of six to eight features and any individual patient rarely has all the core features. Example: VATER (Vertebral Renal dysplasia), CHARGE (Coloboma, Heart defect, Atresia choanae, Growth/MR, genital hypoplasia, Ear abnormalities).
Association is a non-random occurrence of the same multiple anomalies for which no consistent cause can be established
Sequence is used when a single usually undefined event leads to a single anomaly having a cascading effect that causes local and/or distant deformations and/or disruptions, such as Potter sequence (oligohydramnios with beak nose, cartilage-deficient ears, pulmonary hypoplasia) and amniotic band sequence (bands constricting the blood supply to involved limbs with amputation and/or syndactyly), Pierre Robin sequence (micrognathia with glossoptosis and cleft palate).
Dysplasia: Defects resulting from abnormal, cellular organization or function of one tissue type. These may worsen with age e.g., skeletal dysplasia, ectodermal dysplasia.
Complexes: Refer to anomalies of several different structures all of which lie in the same local body region during embryonic development. Many of them are caused by vascular abnormalities. Risk of recurrence is low e.g., hemifacial microsomia, Poland anomaly, sacral agenesis, etc.
Complexes refer to anomalies of several different structures all of which lie in the same local body region during embryonic development.
steps of dysmorphologic evaluation are as follows:
- Suspicion (congenital abnormalities, growth problems, mental retardation)
- History iii. Physical Examination
- Specific Investigations
- Genetic advise/counseling for a known/unknown diagnosis
- Prenatal Diagnosis
History- Elements of dysmorphologic history are included in table 1.
Table 1: Elements of a Dysmorphologic History
- Three generation family history
- Birth defects
- Other genetic disease
- Multiple miscarriages
- Parental ages and health status
- Possible teratogenic exposures
- Results of diagnostic procedures (Ultrasound, Amniocentesis) Complications (Bleeding, High fever)
- Fetal Movement (Time of onset, Vigor)
- Complications of labour
- Fetal presentation
- Mode of delivery
- Neonatal status (Vigor, Anthropometry,
- Breathing, Measurements, Seizures)
- Newborn course (Feeding, Obvious anomalies,
- Complications, Resuscitation)
- Physical growth (Height, Weight, Head circumference)
- Developmental progress (early milestones,
- Formal psychometric testing)
- General health (Illness, Operations, Special studies)
- Any difficulties with vision or hearing. Behavioural phenotype
Physical Examination is of extreme importance and requires skill and an "eye" to pick up abnormalities. Table 2 gives some important dysmorphic features to be looked for. One should use well defined and uncommon handles for search.
Table 2: Physical Examination in Evaluation of a Dysmorphic Children
||Height, weight, head circumference, arm span, US/LS ratio
The further measurements deviates from the normal centile ranges, the greater the change of making a genetic diagnosis
||Shape, size, anterior and posterior fontanelle, forehead and temporal region
||Colour, texture, hair whorl pattern, hair line, growth
||Slant, intercanthal distance, shape, size, cornea, sclera, iris (colour, coloboma), fundus
||Size, position, shape
||Size, shape, palate (narrow, high arched, cleft),
alveolar ridges, lips (thick, thin, cleft, shape), Philtrum (small,
long, simple, prominent)
|Chin & Malar region
||Micrognathia, retrognathia, hypoplasia of malar region
||Short, long, webbed
||Shape, inter nipple distance, sternum
|Hands & Upper limbs
||Shape, fingers, nails, clinodactyly, limb lengths, carrying angle
|Feet & Lower limbs
||Shape, toes, big toe abnormalities, sandal gap, limb lengths, hip dislocation, edema
||Colour, texture, hirsutism, sweating, pigmentary abnormalities |
Synthesis: After detailed history and thorough examination ascertain whether the child is actually dysmorphic/has structural abnormalities or not. If the child has a single anomaly, is it major or minor and provide appropriate therapy and counseling accordingly. If there are multiple minor/major abnormalities classify as dysplasia, deformation, sequence, syndromic, chromosomal or teratogenic diagnosis. Search the London dysmorphology database and OMIM database. Seek help from literature and colleagues. Given below is the simple algorithm Fig 1 and 2 for stepwise approach to dysmorphologic diagnosis.
A large proportion of children do not require any investigation. However some may need following investigations:
- Chromosomal analysis (Karyotype) is needed either for the confirmation of a known chromosomal syndrome or in unrecognized patterns of multiple malformations. Abnormalities of different organ systems along with developmental delay and growth retardation definitely merit chromosomal analysis. In the presence of features specific of microdeletion syndrome FISH analysis should be done.
- Specific molecular tests for single gene defects at DNA level.
- Clinical Photograph to document any significant features and to observe the evolution of features with age (natural history).
- Investigations for Neuro Metabolic or storage disorders enzyme studies, abnormal blood / urinary substrate identification.
- Neuroimaging should be considered in patients without a known diagnosis especially in the presence of neurological symptoms, cranial contour abnormalities, microcephaly or macrocephaly. In most situations MRI is the testing modality of choice.
- Skeletal survey depending upon the disorder being investigated.
- Skin Biopsy for Karyotype in the presence of
a) Streaky skin pigmentation esp. if following the lines of Blashko
c) 3, 4 finger syndactyly with 2, 3 finger syndactyly and bulbous finger tips (diploid/triploid mosaicism). Genetic advise/counseling. For a known diagnosis is usually relatively straight forward.
For unknown diagnosis
- When a diagnosis remains unknown, it is important to spend time in the counseling session explaining the reasons for this. Following is the partial list of certain features and pattern of features suggest a high recurrence risk of up to 25%:
- Previous affected child
- Previous stillbirth / late miscarriages due to fetal abnormalities
- Family history of similarly affected individual
- Neurodevelopmental regression
- Coarsening of facial features
- In the absence of features suggesting a high risk an empiric risk of 5% may be given.
Association complexes and sequences have low risk of recurrence. Denovo chromosomal abnormalities have risk of recurrence of < 1%. In single gene disorders, the risk of recurrence will vary according to mode of inheritance.
Prenatal Diagnosis can be offered in situations where a definitive diagnosis is made e.g., chromosomal and single gene defects where DNA based confirmed diagnosis is possible. In many situations, no definite prenatal testing is possible, however routine antenatal investigations and high resolution ultrasonography for congenital malformations can be rewarding. Level III and 3D ultrasonography can be used successfully to image facial profile and other dysmorphic features.
Surveillance and follow up can help in the following ways:
- To offer newly available diagnostic tests
- To establish that there are no additional medical problems and there is forward developmental progress
- To increase the chance of syndrome recognition. Some dysmorphic syndromes are not easy to diagnose until a few years of age.
- To discuss the recurrence risk.
- Aase JM. Diagnostic Dysmorphology. New York, Plenum Medical Book in 1990
- Jones KL (ed): Smith's recognizable pattern of human malformations ed. Philadelphia, WB Saunders and Company
- Winter RM, Baraitser M. London Dysmorphology Database 2003. www.1mdatabase.com
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|Gupta N, Kabra M.. Available From : http://www.pediatriconcall.com/fordoctor/ Conference_abstracts/report.aspx?reportid=396|