Page 248 - The Netter Collection of Medical Illustrations - Integumentary System_ Volume 4 ( PDFDrive )

Plate 9-7 Integumentary System

Typical facies seen in Down syndrome Variable chromosomal abnormalities leading to trisomy 21
DOWN SYNDROME
Upward-
slanting eyes
Down syndrome is a genetic disorder caused by trisomy with epicanthic
of chromosome 21. Trisomy 21 occurs in approximately folds, flat facies
1 of every 1000 births. Chromosome 21 is an acrocen-
21
tric chromosome, and trisomy 21 is the most common Strabismus 21 21
form of chromosomal trisomy. Trisomy 21 most often Trisomy of chromosome 21
occurs as the result of nondisjunction of meiosis, which Small mouth
leads to an extra copy of chromosome 21. Some patients with protruding
with Down syndrome have a Robertsonian transloca- tongue
tion to chromosome 14 or chromosome 22, which are
two other acrocentric chromosomes. In these cases, the
number of total chromosomes is normal at 46, but the
extra chromosome 21 material is translocated to another
chromosome. This, in effect, causes an extra chromo- 21/22 translocation 22
some 21. All or part of chromosome 21 may be trans- Robertsonian translocation
located, leading to variations in phenotype. Mosaicism Syringomas t (22q; 21q)
is a rare cause of trisomy 21 in partial cell lines, and the
clinical phenotype depends on how early the genetic 14/21 translocation 14
defect occurred during embryogenesis. Robertsonian translocation
Clinical Findings: There is no race predilection in
Down syndrome and only a slightly increased incidence t (14q; 21q)
in males. Down syndrome has been shown to increase
in incidence with increasing maternal age. The esti-
mated incidence increases to 1 in every 50 births for
mothers who are 45 years of age. The clinical manifes-
tations of Down syndrome are wide reaching and affect
every organ system. Patients with Down syndrome have
a decreased life span, although modern medicine con-
tinues to improve these patients’ quality and quantity
of life. Congenital heart disease is one of the most
frequent problems and leads to a plethora of complica- Short, broad
tions and increased morbidity and mortality. Endocar- hands, with
dial cushion defects are the most frequently seen heart simian crease Clinodactyly
abnormality in Down syndrome. Central nervous Brushfield spots on iris and clinodactyly
system involvement leads to mental and physical delay. of fifth digit Simian crease (one
The incidence of childhood leukemia is increased in elongated palmar crease)
these patients, the most frequent type being acute
megakaryoblastic leukemia.
The cutaneous findings in Down syndrome are vast.
All patients with Down syndrome have cutaneous
disease, but because of the variation in phenotype, not
all have the same findings. Patients with Down syn-
drome are more likely to develop atopic dermatitis,
which may be mild or severe. Generalized xerosis is
universally found in Down syndrome. Patients may
have an increase from the normal number of nuchal
skin folds in infancy as well as a characteristic facies.
Epicanthic folds and a flat-appearing face with small
ears and a flattened nose are common. Ophthalmologi-
cal findings include Brushfield spots and strabismus.
Syringomas are frequently seen in Down syndrome Small, hypoplastic ears
and affect the eyelids and upper cheeks. Elastosis perfo-
rans serpiginosa (EPS) is a rare disease caused by the
transepidermal elimination of fragmented elastic tissue.
EPS is seen with a higher incidence in Down syndrome.
The appearance is often that of a thin patch with a Wide gap between Macroglossic fissured tongue
peripheral elevated rim and a polycyclic border or ser- the first and second toes in adults (scrotal tongue)
pentine course. Acanthosis nigricans was shown to be
present in approximately 50% of individuals with Down
syndrome. It can be located in any flexural area, and the
etiology is unknown. The external ear canal has been
shown to be narrowed in a most patients with Down is usually prominent. Alopecia areata is found with who is well aware of the complications and care of
syndrome; this predisposes them to an increased increased incidence in Down syndrome. patients with Down syndrome. The dermatological
number of external and middle ear infections. Macro- Treatment: Patients with Down syndrome require a manifestations are treated as in any other individual,
glossia with a scrotal tongue is frequently encountered. multidisciplinary approach. Cardiac defects tend to and no special considerations are needed. Xerosis
A single transverse palmar crease (simian crease) is cause the most morbidity and mortality, and surgical should be managed with excellent daily skin care. It is
unique to patients with Down syndrome. Shortened intervention to correct underlying heart defects is often important for clinicians to recognize the common cuta-
metacarpal bones lead to smaller-than-normal hands, required. Patients need to be monitored regularly by a neous findings in Down syndrome so that they can
and an extra-wide gap between the first and second toes pediatrician and then an internist or family physician educate parents and patients alike.

234 THE NETTER COLLECTION OF MEDICAL ILLUSTRATIONS