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Addendum A: Clinical features, diagnosis, treatment, genetic counselling and prevention of common birth defects

Single gene defects

Common Autosomal Recessive Disorders

Oculocutaneous albinism

(Autosomal recessive – 1 in 5000 in sub Saharan Africa)

Clinical features:

Skin, hair and retina lack of pigmented

Skin and eye hypersensitivity to sunlight

Increased risk of skin cancer

Reduced visual acuity and nystagmus


Diagnosis:

Clinical diagnosis

DNA diagnosis available**

Treatment and Counselling:

Treat skin infections*

Sunscreen*

Surgery for skin cancer

Glasses for reduced vision

Genetic counselling*

Advice on skin and eye care and coverage with clothes and wide brimmed hats*


Prevention:

1° – Family planning, family history* and preconception DNA carrier screening**

2° – Prenatal carrier screening and prenatal DNA diagnosis**

3° – Early detection* and treatment of skin cancer

Common Autosomal Recessive Disorders

Cystic fibrosis

(Autosomal recessive – 1 in 2000 European and 1 in 2500 in Middle Eastern countries)

Clinical features:

Recurrent chest infections and wheeze

Clubbing of fingers

Chronic diarrhoea

Malabsorption

Failure to thrive


Diagnosis:

Sweat test**

DNA diagnosis**

Treatment and Counselling:

Aggressive treatment of respiratory infections (antibiotics, bronchodilators, physiotherapy)

Pancreatic enzyme replacement

Gene therapy in the future

Genetic counseling**

Prevention:

1° – Family planning, family history* and preconception carrier screening**

2° – Prenatal carrier screening and prenatal diagnosis**

3° – Newborn screen

Sickle cell anaemia

(Autosomal recessive. Birth prevalence varies in different countries – 1 in 50 newborns in Nigeria)

Clinical features:

Moderate to severe haemolytic anaemia

Haemolytic or aplastic crises

Jaundice

Initially splenomegaly but later this disappears

Hyposplenism

Increased susceptibility to infection (especially Streptococcus pneumoniae, Haemophilus influenzae, Salmonella, malaria)

Vaso-occlusive episodes (abdominal including kidneys and spleen, dactylitis, priapism, stroke)

Leg ulcers, aseptic necrosis of bone

Cholelithiasis (gallstones)


Diagnosis:

Full Blood Count-normocytic/mildly macrocytic anaemia, reticulocytosis, target cells

Haemoglobin electrophoresis-increased haemoglobin F and S

Positive sickling test

Increased serum bilirubin

DNA diagnosis**

X-rays - increased medullary spaces and cortical thinning, avascular necrosis of bone

Treatment and Counselling:

Prevention or early treatment of infections (vaccines, antibiotics, anti-malarials)*

Maintain hydration to prevent crises

Manage crises and acute complications

Genetic counselling*


Prevention:

1° – Family planning, family history* and preconception population carrier screening**

2° – Prenatal carrier screening and prenatal diagnosis**

3° – Newborn screening

Rarer Single Gene Defects

Neurofibromatosis I

(Autosomal dominant – 1 in 3000)

Clinical features:

Café-au-lait patches

Neurofibroma

Axillary freckling

Macrocephaly (head circumference above 97th centile)

Scoliosis

Learning difficulties

Complication from compression by neurofibroma

Increased risk of malignancy in neurofibroma


Diagnosis:

Clinical diagnosis

DNA diagnosis available

Neurodevelopmental/psychometric assessment

Treatment and Counselling:

Surgery when indicated and if available

Neurodevelopmental therapy/ community based rehabilitation including psychosocial support

Genetic counselling**


Prevention:

2° – Prenatal diagnosis (DNA diagnosis)


Tuberous sclerosis

(Autosomal dominant – 1 in 15 000)

Clinical features:

Variable expressivity

Adenoma sebaceum and café-au-lait patches

Ash leaf patches and shagreen patches

CNS (cortical) tubers on CT scan

Renal angiomyolipoma

Ungual fibroma

Intellectual disability and epilepsy


Diagnosis:

Clinical diagnosis

DNA diagnosis available

Neurodevelopmental/psychometric assessment

Treatment and Counselling:

Surgery if indicated

Neurodevelopmental therapy/ community based rehabilitation including psychosocial support

Seizure control

Genetic counselling**


Prevention:

2° – Prenatal diagnosis (DNA diagnosis)


Huntington disease

(Autosomal dominant – 1 in 10 000)

Clinical features:

Adult onset (Average age 35 years)

Progressive involuntary movements (chorea)

Progressive dementia and psychiatric symptoms

Weight loss


Diagnosis:

DNA diagnosis*** Presymptomatic testing possible**

Brain scan**

Treatment and Counselling:

No effective treatment. Diagnosis to death averages 15 years

Psychosocial support

Genetic counselling


Prevention:

1° – Family history*, presymptomatic and pre-pregnancy (DNA) diagnosis** and family planning*

2° – Prenatal diagnosis (DNA diagnosis)**

Achondroplasia

(Autosomal dominant 1 in 26 000)

Clinical features:

Skeletal dysplasia with asymmetric short stature (short limbs)

Macrocephaly (head circumference above 97th centile)

Trident hand. May develop hydrocephalus and spinal cord compression


Diagnosis:

Clinical diagnosis

DNA diagnosis available

Treatment and Counselling

Surgery when indicated and if available

Avoid contact sports

Genetic counseling


Prevention:

Genetic counselling**

2° – Prenatal diagnosis (ultrasound** /DNA diagnosis)


Myotonic dystrophy

(Autosomal dominant 1 in 9000)

Clinical features:

Presents usually in young adults. Progressive muscular weakness

Myotonia and frontal baldness

Cataracts

Cardiac conduction defects

Hypogonadism

Congenital form (gene inherited from mother) severe hypotonia, facial diplegia, ptosis, arthrogryposis,cataracts


Diagnosis:

Electromyography (EMG)**

DNA diagnosis**

Treatment and Counselling:

Supportive

Genetic counselling**


Prevention:

1° – Family history* and DNA diagnosis**

Family planning*

2° – Prenatal diagnosis (DNA diagnosis)**


Waardenburg syndrome

(Autosomal dominant – 1 in 30 000)

Clinical features:

Sensorineural deafness

Poliosis (White forelock/early greying)

Sapphire blue eyes or eyes of different colours (heterochromia)

Partial albinism

Telecanthus and medial eyebrow flare


Diagnosis:

Clinical diagnosis

Audiology**

DNA diagnosis**

Treatment and Counselling:

Hearing aid

Neurodevelopmental therapy/ community based rehabilitation including psychosocial support

Genetic counselling**


Prevention:

Nil


Congenital hypothyroidism

(Autosomal recessive 1 in 4000)

Clinical features:

Feeding problems

Decreased activity

Constipation

Macroglossia (Large tongue)

Hypothermia and dry skin

Umbilical hernia

Intellectual disability/deafness


Diagnosis:

Thyroid function tests – Thyroid stimulating hormone (TSH)

Free thyroxine (T3 and T4)**

Neurodevelopmental/psychometric assessment**

Audiological testing (Pendred syndrome – have deafness)**

Treatment and Counselling:

Growth monitoring*

Thyroxine

Neurodevelopmental therapy/ community based rehabilitation including psychosocial support

Genetic counselling**


Prevention:

3° – Newborn screening (Not presently done universally in South Africa)

Fragile X syndrome

(X-linked recessive 1 in 2000 males)

Clinical features:

Intellectual disability

Speech disability

Autistic-like behaviour

Macrocephaly

Long narrow faces with large ears

Testicular enlargement


Diagnosis:

DNA diagnosis**

Neurodevelopmental/psychometric assessment**

Neurodevelopmental therapy/ community based rehabilitation including psychosocial support.

Treatment and Counselling:

Genetic counselling**


Prevention:

1° – Family history* and carrier screening**

Family planning*

2° – Prenatal diagnosis (DNA diagnosis)**


Haemophilia A and B

(X-linked recessive – Haemophilia A 1 in 2000 males/Haemophilia B 1 in 20 000 males)

Clinical features:

Spontaneous bleeding disorder

Variable clinical expression

Haemarthrosis


Diagnosis:

Prolonged partial thromboplastin time

Decreased factor VIII (A) or IX (B) in blood**

DNA diagnosis available**

Treatment and Counselling:

Replace factor VIII (A) or IX (B)*

Pain relief*

Splinting*

Physiotherapy/CBR*

Genetic counselling*


Prevention:

1° – Family history* and DNA carrier screening**

Family planning*

2° – Prenatal diagnosis (DNA diagnosis)**

3° – Avoid injury

Duchenne Muscular Dystrophy

(X-linked recessive 1 in 3700 males)

Clinical features:

Clinical onset 3–5 years of age

Gait abnormalities

Weakness of the pelvic girdle

Gower sign

Pseudohypertrophy of the calves

Tightening of the Achilles tendons

Lumbar lordosis

Progressive muscle weakness and atrophy of muscles

Loss of ability to walk by 9-16 years

Cardiomyopathy/heart failure

Respiratory failure

Death by 25 years


Diagnosis:

High creatine phosphokinase (CPK)

DNA diagnosis**

Treatment and Counselling:

Physiotherapy

Surgery if indicated**

Cardiac failure treatment*

Treatment of respiratory infection*

Wheel chair

Genetic counselling**


Prevention:

1° – Family history* and DNA carrier screening**

Family planning* and 2° – prenatal diagnosis (DNA diagnosis)**

Chromosomal disorders

Down syndrome

Currently 1 in 500 live births in South Africa

Clinical features:

Hypotonia

Intellectual disability

Craniofacial: brachycephaly, flat face, up-slanting palpebral fissures, epicanthic folds, flat nasal bridge, small, low set ears, squint, relative macroglossia, Brushfield spots (Caucasians)

Short stature

Brachydactyly, single palmar creases, 5th finger clinodactyly and hypoplasia mid-phalanx

Sandal gap between first and second toes, plantar creases

Small penis/hypogonadism

Congenital heart disease

Duodenal atresia

Recurrent infection, especially of the respiratory tract


Diagnosis:

Chromosomal/ FISH analysis/QR-PCR**

Trisomy 21 – 95%

Mosaicism – 2.5%

Translocation – 2.5%

Thyroid function tests

Neurodevelopmental/psychometric assessment

Cardiac assessment

Audiology

Treatment and Counselling:

Growth monitoring

Surgery when indicated and available

Treatment for cardiac failure*

Treatment of infections*

Thyroxine if indicated

Neurodevelopmental therapy/ community based rehabilitation including psychosocial support

Genetic counselling*


Prevention:

1° – Family planning and preconception care*

2° – Prenatal (AMA) screening* Ultrasound and maternal serum screening for Down syndrome

Prenatal chromosome/QR-PCR diagnosis**

Trisomy 18

(1 in 1500 live births)

Clinical features:

Decreased fetal movement. Prenatal growth deficiency

Severe developmental delay

Hypertonia with weak cry, poor sucking

Craniofacial: bifrontal narrowing, prominent occiput, microcephaly, low set malformed ears, short palpebral fissures, small chin and mouth, cleft lip/palate

Clenched hands, overriding fingers

Rocker-bottom feet, clubfeet

Congenital heart disease

Genital hypoplasia

Neonatal or early infant death

Diagnosis:

Chromosomal/ FISH analysis/QR-PCR**

Treatment and Counselling:

Supportive/ Palliative care*

Genetic counselling*

Supportive


Prevention:


1° – Family planning and preconception care*

2° – Prenatal screening for chromosomal disorders

Ultrasound scanning for birth defects.

Prenatal diagnosis. Chromosomal/ FISH analysis/QR-PCR.**


Trisomy 13

(1 in 4500 live births)

Clinical features:

Prenatal growth deficiency

CNS malformations

Hypertonia/hypotonia with severe developmental delay

Craniofacial: Microcephaly/ sloping forehead, microphthalmia, anophthalmia, abnormal ears, cleft lip/palate, micrognathia

Polydactyly, camptodactyly, convex hypoplastic finger nails, cryptorchidism

Congenital heart disease

Neonatal or early infant death

Diagnosis:

Chromosomal/ FISH analysis/QR-PCR.**

Treatment and Counselling:

Supportive/ Palliative care*

Genetic counselling*


Prevention:

1° – Family planning and preconception care*

2° – Prenatal screening for chromosomal disorders

Ultrasound scanning for birth defects

Prenatal chromosome diagnosis**


Turner syndrome

(1 in 1000 female live births)

Clinical features:

Female phenotype

Short stature

Congenital heart disease (aortic stenosis/ coarctation of aorta)

Renal anomalies

Ovarian dysgenesis/infertility

Learning difficulties


Diagnosis:

Chromosomal/ FISH analysis/QF-PCR**

Monosomy XO/ Turner mosaics

Neurodevelopmental/psychometric assessment

Cardiac assessment

Treatment and Counselling:

Growth monitoring*

Surgery when indicated and if available**

Ovarian hormone replacement therapy**

Neurodevelopmental therapy/ community based rehabilitation including psychosocial support

Genetic counselling**

Prevention:

1° – Family planning and preconception care*

2° – Prenatal screening for chromosomal disorders

Ultrasound scanning for birth defects

Prenatal diagnosis. Chromosomal/ FISH analysis/QR-PCR**

Multifactorial disorders

Spina bifida

Clinical features:

Spinal lesion with paraplegia/ incontinence

Hydrocephalus and developmental delay


Diagnosis:

Clinical diagnosis

Brain ultrasound/ CAT scan

Urological assessment

Neurodevelopmental/psychometric assessment

Treatment and Counselling:

Surgery when indicated and if available

Incontinence care

Neurodevelopmental therapy/ community based rehabilitation including psychosocial support

Palliative care*

Prevention:

Genetic counselling*

1° – Optimising women’s diet. Folic acid supplementation*

2° – Maternal serum alpha feto-protein screening

Ultrasound scanning for birth defects

Anencephaly

Clinical features:

Incomplete development and closure of the skull and development of the brain.

Incompatible with life.


Diagnosis:

Clinical diagnosis.

Treatment and Counselling:

Palliative care*

Prevention:

Genetic counselling.*

1° – Optimising women’s diet. Folic acid supplementation.*

2° – Maternal serum alpha feto-protein screening.

Ultrasound scanning for birth defects.

Encephalocele

Clinical features:

Incomplete closure of the skull with out-pouching containing neural tissue.

Microcephaly.

Developmental delay.

Seizures.


Diagnosis:

Clinical diagnosis.

Brain scan.

Neurodevelopmental/psychometric assessment.

Treatment and Counselling:

Surgery when indicated and if possible.

Neurodevelopmental therapy/ community based rehabilitation including psychosocial support.

Seizure control.

Genetic counselling*


Prevention:

1° – Optimising women’s diet. Folic acid supplementation.*

2° – Ultrasound scanning for birth defects.

Cleft lip/palate

Clinical features:

Cleft lip and/or palate.

Feeding problems.

Speech difficulties.


Diagnosis:

Clinical diagnosis.

Audiology.

Treatment and Counselling:

Surgery.

Feeding plate in infancy.

Neurodevelopmental therapy/ community based rehabilitation including psychosocial support.

Genetic counselling.*


Prevention:

Nil.

Talipes equinovarus

(Clubfoot)

Clinical features:

Fixed equinovarus deformation of the foot (feet).

X-rays.


Diagnosis:

Clinical diagnosis.

Treatment and Counselling:

Manipulation and plaster of Paris casts.

Surgery when indicated.

Genetic counselling.*


Prevention:

Nil.

Teratogens

Fetal alcohol syndrome

(Prevalence varies between communities. Estimated more than 1% of South African infants are born with FAS)

Clinical features:

Pre- and post natal growth deficiency.

Microcephaly.

Intellectual disability.

Behaviour disorder.

Craniofacial: short palpebral fissures, short upturned nose, smooth philtrum, thin vermillion border.

Joint anomalies.

Congenital heart defects.


Diagnosis:

Clinical diagnosis.

Treatment and Counselling:

Neurodevelopmental/psychometric assessment.

Cardiac assessment.

Growth monitoring.*

Surgery when indicated and if available.

Neurodevelopmental therapy/ community based rehabilitation including psychosocial support.

Neuro-behavioural management.

Genetic counseling.*


Prevention:

1° – Optimising women’s diet.

Public education on the bad effects of alcohol use and abuse in pregnancy.*

Fetal rubella syndrome

Clinical features:

Growth deficiency.

Microcephaly.

Intellectual disability.

Sensori-neural deafness.

Cataracts, chorioretinitis, microphthalmia, squint.

Congenital heart disease (PDA, septal defects, peripheral pulmonary stenosis).

Hepatosplenomegaly.

Thrombocytopenia, anaemia.


Diagnosis:

Clinical diagnosis.

Serum IgG and IgM for rubella. Identify virus in urine.

Neurodevelopmental/psychometric assessment.

Visual assessment.

Audiology.

Cardiac assessment.

Full Blood Count.

Treatment and Counselling:

Growth monitoring.*

Surgery when indicated and if available.

Auditory and vision management.

Neurodevelopmental therapy/ community based rehabilitation including psychosocial support.

Genetic counselling.*


Prevention:

1° – Preventing maternal infection by mass rubella immunisation.

2° – Prenatal screening for sero-negativity and immunisation prior to subsequent pregnancy.*

Detection of congenital malformations with ultrasound screening.

Avoid contact between pregnant women and ill children


Abbreviations:

* Possible in primary health care.
** Available in South Africa
1° – Primary prevention (Preconception and early postconception period).
2° – Secondary prevention (Antenatal period).
3° – Tertiary prevention (Postnatal period).
CBR. Community-based rehabilitation
FISH. Fluorescent in situ hybridisation

(Adapted from Christianson A L and Modell B. Medical Genetics in Developing Countries, Ann. Rev. Genomics Hum Genetics. 2004;5: 219–265).