An inherited disorder characterized by encephalocele, vitroretinal degeneration with retinal
detachment, high myopia, and normal intelligence. Because all patients have
normal intelligence, it is suggested that the cephalocele is a meningocele
rather than an encephalocele.
Vitreoretinal Degeneration with Retinal Detachment, and
Occipital Cephalocele; Knobloch-Layer Syndrome; Retinal Detachment and
Occipital Encephalocele Syndrome.
Approximately 35 patients have been reported in the literature.
Autosomal recessive, caused by defective collagen XVIII. Gene map locus is 21q22.3.
Penetrance seems to be 100%; however, variability (intraand interfamilial) is considerable.
Condition controlled by a mutation in the COL18A1
collagen gene that is of variable expressivity. The cranial and eye
alterations in this syndrome may occur early in embryogenesis, suggesting
that developmental genes may be involved in the pathogenesis of this
Made based on the clinical findings. Histology may reveal
heterotopic neuronal tissue in the skull lesions (thereby distinguishing between scalp
defect and encephalocele).
The most common findings are high myopia, vitreoretinal degeneration with retinal
detachment, and occipital encephalocele. Intellegence is usually normal. This led to the
assumption, that in many cases the encephalocele may in fact be either a meningocele or a
scalp defect. Heterotopic neuronal tissue could be found in the scalp lesions of some
patients. Other reported, but inconstant findings include Scimitar Syndrome, patent
ductus arteriosus, single umbilical artery, mild congenital pulmonary lymphangiectasia (visible on chest radiographs as
interstitial changes), and abnormal palmar creases.
A complete history and thorough examination is required. Ask about pulmonary problems (respiratory distress, cyanosis, cough)
and rule out encephalocele (important for positioning of the patient).
If an occipital encephalocele/ meningocele is present, induction of anesthesia is best
performed in the left lateral position or alternatively on bolsters avoiding any pressure
on the lesion. Congenital pulmonary lymphangiectasia is often fatal in the neonatal
period; respiratory distress has not been described in these patients, which probably
indicates a mild form of congenital pulmonary lymphangiectasia. However, the threshold for
a chest radiograph and/or an arterial blood gas analysis should be kept low. Increases in
intraocular pressure should be avoided in patients at risk for retinal detachment.
Since succinylcholine is known to potentially increase intraocular pressure, it should
best be avoided in these patients with a high risk of retinal detachment.
Meckel-Gruber Syndrome (MKS): Autosomal recessive disorder characterized
by the presence of renal cysts, developmental anomalies of the central
nervous system (e.g., posterior encephalocele most often defined as an
occipital scalp defect), hepatic ductal dysplasia and cysts, and
Myllyharju J, Kivirikko KI: Collagens and collagen-related diseases. Ann Med
Sniderman LC, Koenekoop RK, O'Gorman AM, et al: Knobloch syndrome involving
midline scalp defect of the frontal region. Am J Med Genet
Suzuki OT, Sertie AL, Der Kaloustian VM, ...