Genetic disorder with unfavorable prognosis
manifesting as blindness, mental retardation, and characteristic skeletal
Unknown. Approximately 15 cases have been reported.
Both autosomal recessive (common) and X-linked
recessive transmission (rare) have been reported. Parental consanguinity is
considered a risk factor.
Dysplasia of the bone with areas of thickening and
areas of sclerosis is responsible for this very distinctive osseous disease.
However, the underlying mechanism is unknown.
Made by clinical course and findings of the disorder in
combination with the typical radiologic features.
Most typical radiologic finding is platyspondyly
(flattening of the vertebral bodies), especially of the thoracic spine with
irregular endplates and wide intervertebral spaces. As in osteopetrosis,
vertebral bodies and the ribs show a diffusely increased density. Sclerosis
is found in the diaphyses and epiphyses of the long bones. The metaphyses
are splayed and osteoporotic as a result of cortical thinning, particularly
in the lower extremities. Metaphyseal widening extends progressively with
time. There is an increased risk of fractures even after trivial trauma.
Thickening and sclerosis of the skull base result in macrocephaly and
impingement of the basal foramina but particularly of the optic nerve canal,
causing optic atrophy with severe visual impairment or blindness, which
probably is the most important clinical finding. The electroretinogram and
visual evoked potentials confirm the gross loss of function of visual
pathways. Other radiologic findings include thickening and sclerosis of the
clavicles and scapulae and absent pneumatization of the paranasal sinuses
and the mastoids. Less commonly, hearing impairment or deafness may occur.
Growth hormone levels are abnormally low, resulting in progressive growth
retardation. Occasionally, hydrocephalus, hypertelorism, and micrognathia
with a high arched palate and excessive drooling are found. Progressive
mental retardation with loss of acquired milestones, sometimes associated
with seizures, is another important clinical finding. Dental hypoplasia with
delayed eruption of the first teeth and failure of the permanent teeth to
erupt are frequent findings. The teeth themselves are of diminished quality,
fall out prematurely, and show significant cavities. Macular, violet, or
dark rose areas of skin atrophy, which are caused by discrete fragmentation
and rarefaction of the elastic layer in the middle and deep sections of the
dermis, and flattening of the fingernails may occur.
Evaluate the degree of micrognathia.
If drooling is excessive, consider anticholinergic premedication. Assess the
severity and locations of skeletal lesions. If an epidural or spinal
anesthesia is planned, consider obtaining radiographs of the spine.
If micrognathia is significant enough to
generate any doubt about airway management, consider fiberoptic tracheal
intubation while maintaining spontaneous ventilation. Apply the standard
measures for management of increased intracranial pressure in the presence
of hydrocephalus. The tendency for bones to fracture easily and the skin
changes warrant careful positioning and padding. Regional anesthesia (e.g.,
epidural or spinal) may be challenging because of the dysplastic vertebrae.
Mental retardation and blindness can make cooperation difficult. Careful
sedative and anxiolytic ...