Case 29 Flashcards
What are key findings from history in a 4 day old child with down syndrome?
Hypotonia, sleeps a lot, feeds well when awake, normal birth weight, no prenatal testing
What are key findings from PE in a 4 day old child with down syndrome?
Reflexes present, flattened mid-face and epicanthal folds, incurving of fifth fingers, normal cardiac exam, mild diastasic recti. (separation of abdominal muscles)
What is on the differential diagnosis for down syndrome?
Perinatal asphyxia, metabolic abnormalities, effects of maternal medications, chromosome abnormalities, benign neonatal hypotonia, Sepsis, CNS abnormalities.
What are findings from lab testing for Down Syndrome?
Lymphocyte karyotype demonstrates Trisomy 21
Syndromes with mental retardation:
- Down Syndrome
- Trisomy 13 (Patau syndrome)
- Trisomy 18 (Edwards syndrome)
- Fragile X syndrome
What are syndromes involving sex chromosomes?
Turner syndrome (45XO), Klinefelter syndrome (47XXY)
Down syndrome:
- Trisomy 21 is probably the most common cause of mental retardation that involves genetic material
- Several karyotypes involving extra material from chromosome 21 can cause Down syndrome phenotype:
- -Trisomy 21 is most common and most likely, regardless of mother’s age
- -Unbalanced chromosome translocations that result in extra chromosome 21 material
- -Mosaicism for a trisomy 21 cell line
- Syndrome is present in about 1 in 700 births in the US
- Clinical features may include mental retardation, epicanthic folds and flat facial profile, single palmar crease, redundant neck skin, heart defects, intestinal stenosis, umbilical hernia, predisposition to leukemia, hypothyroidism, hypotonia, short stature, and a gap between the first and second toes.
What are risk factors for down syndrome?
- Maternal age greater than 35 years at delivery is a significant risk factor for having a child with down syndrome, although majority of down syndrome pregnancies occur to women under age 35
- No strong paternal age effect
- Consanguinity is not a risk factor
Trisomy 13 (Patau syndrome):
- Incidence: 1/10,000 births
- Clinical features include microphthalmia, microcephaly, and severe mental retardation, polydactyly, cleft lip and palate, cardiac and renal defects, umbilical hernia, and cutis aplasia.
Trisomy 18 (Edwards syndrome):
- Incidence: 1/6,000 births
- Clinical features may include severe mental retardation, prominent occiput, micrognathia, low-set ears, short neck, overlapping fingers, heart defects, real malforatmions, limited hip abduction, rocker-bottom feet.
Fragile X syndrome:
- Fragile X syndrome is the most common familial cause of mental retardation
- Caused by the inheritance of an abnormal number of trinucleotide (CGG) repeats outside the coding region of the FMR1 gene on the X chromosome
- Clinical features may include large testicles (after puberty); large, everted ears; long face with large mandible
Turner Syndrome:
(45XO)
- Incidence: 1/2000 female live births (but about 99 percent of conceptuses with Turner syndrome miscarry)
- Normal IQ
- More likely to be associated with physical differences at birth
- Associated findings: Lymphedema in utero (cause of many physical findings, including webbed neck, low placement of ears, edema of the hands and feet), hyper convex nails, “shield” chest, widely spaced nipples
- Coarctation of the aorta found in about 20 percent of affected girls
- Short stature
- Gonadal dysgenesis
Klinefelter syndrome:
(47XXY)
- Boys with Klinefelter syndrome are usually normal at birth
- IQ varies, but is usually in the low-normal range
- Findings vary but usually include infertility due to testicular atrophy
- May be a eunuchoid body habits and gynecomastia in adolescence.
Features seen in an infant with trisomy 21:
Remember that almost all of these findings may be seen individually in people who do not have Down syndrome; it is the combination of findings that separates a syndrome from a normal variationL
-Upslanting palpebral fissures
-Epicanthal folds
-Small ears (usually less than 34 mm at maximum dimension in a term infant)
-Flattened midface
-Redundant nuchal skin
-Single palmar crease
-Incurving of fifth finger
-Hypotonia
-Diastasis recti (a ridgelike separation between the left and right side of the rectus abdominis muscle)
-Cleft lip or palate may be seen at a rate higher than that of the general population, but still is not common
As child grows, since short stature is very common finding, important to use growth chart specific for children with Down Syndrome.
What are more likely differential diagnosis for Down Syndrome?
Benign neonatal hypotonia (congenital hypotonia), Down Syndrome, Zellweger syndrome