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Genetic disorder leading to skeletal dysplasia.
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Kniest-like Dysplasia with Pursed Lips and Ectopia Lentis.
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Only three cases reported in the literature.
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First described in two siblings, one male and
one female. A second case in a 2-year-old girl subsequently was reported.
Mode of inheritance is uncertain, but autosomal recessive or gonadal
mosaicism is most likely.
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Iliac bone biopsy reveals markedly abnormal
cartilage matrix in certain areas with large clumps of aggregated collagen
fibrils. The growth plates are shorter than normal; however, the resultant
calcified cartilage and bone trabeculae appear normal. Electron microscopy
confirms the presence of broad-banded, aggregated collagen fibers, 10 to 30
times broader than normal, scattered throughout the cartilage matrix.
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Based on the characteristic clinical and radiologic
findings. The analysis of bone biopsy specimens reveals distinctive
abnormalities in the cartilage matrix.
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Characterized by short stature (< 3rd percentile), shortness and
bowing of limbs, bell-shaped thorax with flaring of lower ribs, short neck,
rhizomelia, talipes equinovarus, mild craniofacial disproportion, stiffness,
and swelling of wrists and knees. Other features include microstomia high-arched palate, pursed
lips, and ectopia lentis. Radiologic findings of platyspondyly with cervical
kyphosis resulting in decreased neck mobility, pectus carinatum, increased lumbosacral angle, bowing and shortening of the lower
limbs, dumbbell-shaped long bones, short diaphyses, flared metaphyses and
metaphyseal sclerosis, delayed ossification of the femoral heads and dysplastic femoral necks, wide short ribs, short and broad pelvis with narrow
sacrosciatic notches, and brachydactyly are present. Unlike Kniest
dysplasia, coronal clefts are absent. Psychomotor development appears normal
for age.
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Preoperative assessment should
include a full history and examination. Careful assessment of the airway to
determine the potential for difficult airway management (microstomia,
cervical kyphosis and limitation of neck movements reported by age 1.5
years). Radiologic investigation to assess neck stability may be required in
the presence of cervical vertebral dysplasia. Anticholinergic premedication
to decrease secretions can be of value in the younger age group,
particularly if difficult airway management and/or fiberoptic intubation is anticipated. Use lung
function tests to assess respiratory function.
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Induction of anesthesia must take into
consideration the potential for difficult airway management (small mouth, reduced neck mobility). A gaseous
induction with halothane or sevoflurane may be advisable with a selection of
devices available for control of the airway and tracheal intubation. During
anesthesia, the neck should be maintained in a neutral or slightly extended
position with adequate neck support at all times. Although not reported as being
a problem in infants with this syndrome, respiratory insufficiency following
anesthesia may be a potential risk in these children as they become older
and the degree of thoracic dystrophy increases. Preoperative assessment and
the nature of the surgery should enable the anesthesiologist to determine if
postoperative respiratory support will be required. The patient should be
positioned carefully with adequate padding and support to all areas because
of fixed deformities in the limbs and neck. Regional anesthesia is not
contraindicated, but because of the vertebral abnormalities and joint stiffness associated with
this syndrome central neuraxial anesthesia could be difficult to perform and
should be reserved for patients in whom the benefits outweigh the risks of other
alternative forms of pain relief.
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No known specific pharmacological
implications.
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Kniest Dysplasia: Autosomal dominant inherited collagen type II
disorder resulting in defective cartilage with craniofacial and spinal
abnormalities. (Kniest Syndrome).
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Freeman-Sheldon Syndrome (FSS): An inherited disorder characterized by microstomia (small,
pinched mouth mimicking whistling), club feet and contractures of fingers.
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