Mutations in NYX, encoding the leucine-rich proteoglycan nyctalopin, cause X-linked complete congenital stationary night blindness

During development, visual photoreceptors, bipolar cells and other neurons establish connections within the retina enabling the eye to process visual images over approximately 7 log units of illumination. Within the retina, cells that respond to light increment and light decrement are separated into ON- and OFF-pathways. Hereditary diseases are known to disturb these retinal pathways, causing either progressive degeneration or stationary deficits. Congenital stationary night blindness (CSNB) is a group of stable retinal disorders that are characterized by abnormal night vision. Genetic subtypes of CSNB have been defined and different disease actions have been postulated. The molecular bases have been elucidated in several subtypes, providing a better understanding of the disease mechanisms and developmental retinal neurobiology. Here we have studied 22 families with 'complete' X-linked CSNB (CSNB1; MIM 310500; ref. 4) in which affected males have night blindness, some photopic vision loss and a defect of the ON-pathway. We have found 14 different mutations, including 1 founder mutation in 7 families from the United States, in a novel candidate gene, NYX. NYX, which encodes a glycosylphosphatidyl (GPI)-anchored protein called nyctalopin, is a new and unique member of the small leucine-rich proteoglycan (SLRP) family. The role of other SLRP proteins suggests that mutant nyctalopin disrupts developing retinal interconnections involving the ON-bipolar cells, leading to the visual losses seen in patients with complete CSNB.

Evidence supportive of a functional discrimination between photopic oscillatory potentials as revealed with cone and rod mediated retinopathies

We report on a family where four of the eleven children presented with reduced visual acuities, a red-green deficit at the Farnsworth-Munsel FM 100-hue test, normal appearing fundi and unexpected electroretinographic findings. Light- (photopic) and dark- (scotopic) adapted electroretinograms (ERG) and oscillatory potentials (OPs) were obtained following an accepted standard protocol. The b-wave of their photopic ERG was significantly more attenuated than the a-wave due to the specific abolition of OP4, while the amplitudes of OP2 and OP3 were within the normal range, giving to the b-wave a truncated appearance reminiscent of that seen in congenital stationary night blindness (CSNB) with myopia. Interestingly in the latter condition, which is believed to result from an ON-retinal pathway anomaly, it is OP2 and OP3 which are specifically abolished while OP4 is of normal amplitude thus resulting in an OP response pattern which complements that seen with our patients. Also of interest is the fact that, in our patients, the amplitude of the dark-adapted OP2 was, on average, 240% larger than that measured in light-adaptation while, in normal, a non-significant 14% increase is noted; a finding which is in keeping with other studies reporting supernormal scotopic ERGs in some forms of cone dystrophies. Based on the photopic OP response pattern, our patients represent the electrophysiological complement of patients affected with CSNB. Interestingly their symptoms are also complementary, a finding which could support a functional discrimination between the photopic OPs.

Can interocular pattern reversal visual evoked potential and motor reaction time differences distinguish anisometropic from strabismic amblyopia?

PURPOSE

With the use of the pattern reversal visual evoked potential and the motor reaction time, we sought to differentiate anisometropic amblyopia from strabismic amblyopia on the basis of the visual transmission time.

METHODS

Pattern reversal visual evoked potentials and motor reaction times were obtained in nine normal subjects, eight anisometropic and seven strabismic amblyopes.

RESULTS

Our results show that while the peak time of the pattern visual evoked potential in anisometropic amblyopia and strabismic amblyopia was significantly delayed, it could not distinguish the two types of amblyopia. In contrast, a significantly longer interocular increment in strabismics compared to anisometropes was found with the reaction time, but not with the pattern visual evoked potential.

CONCLUSION

Our findings thus show that it is possible to distinguish strabismic from anisometropic amblyopes using interocular differences in reaction time measurements. Our results bring support to the contention that the two types of amblyopia represent different neural abnormalities.

Arthrogryposis multiplex congenita, craniofacial, and ophthalmological abnormalities and normal intelligence: a new syndrome?

We report on an 8-year-old boy with clinical manifestations suggestive of a new arthrogryposis syndrome. These included characteristic craniofacial abnormalities, cleft palate, arthrogryposis multiplex congenita, pulmonary hypoplasia, cryptorchidism, and unusual ophthalmological findings. There was no intrauterine growth retardation or decreased fetal movements. Despite the poor prognosis expected in early life, the patient presented with normal mental capability on follow-up. Family data showed that a maternal first cousin of the mother (mother's brother's son) had similar findings and died in infancy. Differential diagnosis included Pena-Shokeir syndrome or phenotype, Gordon syndrome, Marden-Walker syndrome, and the syndrome of arthrogryposis with ophthalmoplegia and retinopathy. The possibility of autosomal dominant inheritance with reduced penetrance is suggested for this apparently new syndrome.

Progressive encephalopathy with edema, hypsarrhythmia, and optic atrophy (PEHO syndrome)

Progressive encephalopathy with edema, hypsarrhythmia, and optic atrophy syndrome is a recently described rare disorder of infantile regression, intractable seizures, and cerebellar atrophy that occurs almost exclusively in the Finnish population. We report the first North American child with this condition.

Clinical evaluation of aminocaproic acid for managing traumatic hyphema in children

PURPOSE

The purpose of this study is to determine the incidence of secondary hemorrhage after traumatic hyphema in children and to evaluate the efficacy of epsilon aminocaproic acid in reducing this incidence.

METHODS

In a prospective, randomized, double-blind study performed between November 1987 and February 1994, 94 children admitted for traumatic hyphema were assigned to receive either aminocaproic acid (n = 48) (100 mg/kg every 4 hours; maximum, 30 g daily) or placebo (n = 46) for 5 days. Patients who had ingested aspirin in the week preceding admission were excluded from the study.

RESULTS

Mean age of the patients was 9.4 years. Black patients comprised 4% of the study population. Secondary hemorrhage occurred in only three patients (3.2%), two from the placebo group and one from the aminocaproic acid group, none of whom had any complications. The duration of hospital stay and the clot resorption times were increased significantly in the aminocaproic acid group (P < 0.001).

CONCLUSIONS

The authors report a very low incidence of secondary hemorrhage compared with most previous studies. This difference is likely related to the small proportion of black patients in our study and to the exclusion of patients having ingested aspirin, two factors that seem to be associated with higher rates of rebleeding. The efficacy of aminocaproic acid could not be determined due to the low incidence of hemorrhage. The results of this study, however, suggest that the incidence of secondary hemorrhage in white patients without prior ingestion of aspirin is insufficient to justify routine use of aminocaproic acid in managing traumatic hyphema. Rather, an individualized decision based on the risk factors of each patient would seem more appropriate to avoid a slower clot resorption time and possible side effects of this medication.

Monocular contribution to the peak time of the binocular pattern visual evoked potential

The contribution of each monocular pathway to the timing of the binocular pattern visual evoked potential was assessed in situations where a significant interocular timing discrepancy was observed. Monocular and binocular pattern visual evoked potentials to 0.5 degree checks were recorded from normal subjects, normal subjects in whom one eye was blurred, patients with monocular amblyopia, and patients with resolved unilateral optic neuritis. Normal subjects showed facilitation, while suppression was evidenced in subjects with monocular blurring. In patients with amblyopia, the affected pathway had no effect on binocular pattern visual evoked potential latency, suggesting that the amblyopic eye was suppressed. In contrast, all patients with optic neuritis showed binocular averaging. Our results show that different forms of binocular interaction are evidenced in normal subjects, in amblyopia and in optic neuritis, and suggest that a comparative analysis of monocular and binocular pattern visual evoked potential peak times brings valuable information to the clinical evaluation that could be used to distinguish disease processes further.

Human strabismus: evaluation of the interhemispheric transmission time and hemiretinal differences using a reaction time task

Experimentally induced strabismus in visually immature cats leads to abnormal development of the posterior corpus callosum. This, in turn, should lead to abnormal interhemispheric integration of unilaterally presented visual information. To test whether strabismus produces deficits in the human commissural visual system, the interhemispheric transmission time (ITT) was compared in strabismic and normal subjects. Simple unimanual reaction times (RT) were tested in 30 subjects in response to a lateralized target presented monocularly at 4 degrees and 35 degrees nasally and temporally from the fovea along the horizontal meridian. This method was also used to examine the effect of strabismus on the central and peripheral portions of each hemiretina. The results showed that in strabismic subjects with or without amblyopia, the ITT did not differ significantly from normals at both eccentricities. In non-amblyopic strabismic patients, RTs in the central and peripheral portions of hemiretina were comparable to normals. However, a reduced speed of response was found in the central visual field (4 degrees) in the amblyopic eye. Our results suggest that the ITT is normal in strabismic subjects and that the longer RTs in the central portion of the nasal and temporal hemiretina of the amblyopic eye may be associated with the severe amblyopic condition.

Ocular findings and visual evoked potential response in the Prader-Willi syndrome

It has recently been suggested that aberrant misrouting of retino-geniculate-cortical (RGC) projections, a finding previously noted only in albinism, may be an additional feature of the Prader-Willi syndrome. To determine the prevalence of ocular abnormalities in patients with the syndrome and to look for evidence of misrouted RGC projections by means of testing of the pattern-onset visual evoked potential (VEP) response, we examined 12 patients with Prader-Willi syndrome, 8 albino subjects and 5 healthy control subjects. Ocular findings in the first group included telecanthus (in five subjects), strabismus, nystagmus, foveal hypoplasia, visual field defects and cataract. However, the VEP asymmetry typically seen in albinism was not noted in any of the patients with Prader-Willi syndrome. Our findings do not support previous claims of abnormal optic nerve fibre decussation in Prader-Willi syndrome.

The importance of congenital hypertrophy of the retinal pigment epithelium in familial adenomatous polyposis

We describe a family with familial adenomatous polyposis (FAP) and congenital hypertrophy of the retinal pigment epithelium (RPE). Three of five members with FAP showed flat, well-demarcated, round to oval pigmented patches of congenital hypertrophy of the RPE. We stress the importance of congenital hypertrophy of the RPE as a clinical marker in identifying patients with FAP since they are at risk for cancer.

Jaw muscle tension after succinylcholine in children undergoing strabismus surgery

The increases in tension at the masseter and adductor pollicis muscles following succinylcholine, 1 mg.kg-1, during halothane anaesthesia were measured in eight children, 3-10 yr, with strabismus. The results were compared with those obtained in a control group of general surgical patients. Supramaximal train-of-four (TOF) stimulation was applied to the ulnar nerve and the nerve to the masseter simultaneously. Jaw closure was measured by a force transducer system. In all patients, succinylcholine caused an increase in resting tone at the jaw and at the thumb. In the strabismus group, the magnitude of this increase was 55.7 +/- 23.2 g, mean +/- SD, at the jaw and 11.3 +/- 5.6 g at the thumb. This was not significantly different from the values obtained in controls, 45.3 +/- 33.4 g and 7.9 +/- 4.2 g, respectively. The duration of the phenomenon was 1-2 min in both muscles studied, and was not statistically different in the strabismus group. Time to complete neuromuscular blockade was significantly faster at the masseter, 31 +/- 6 sec--control groups; 39 +/- 11 sec--strabismus group, than at adductor pollicis, 61 +/- 34 sec--control groups; 75 +/- 28 sec--strabismus group (P less than 0.05 and 0.013 respectively). It is concluded that succinylcholine causes similar increases in jaw tension and comparable degrees of neuromuscular blockade in patients undergoing strabismus surgery as in other children.

The effect of diphenylhydantoin on the electroretinogram

Acute administration of diphenylhydantoin (DPH) in rabbits produces a significant increase in the amplitude of the a-wave. A marked increase in the amplitude of the b-wave is also noted but the time course is slower than that for the a-wave. While in controls the oscillatory potential (OP) recordings essentially consist of three major types, recordings taken after DPH injection consist of one major OP (OP2), which appears to be a result of the fusion of the original OP2 with another OP produced by the DPH injection. A similar blend of OPs was also seen in ERGs recorded from three human subjects on DPH therapy.

Abnormal dark-adapted electroretinogram in Best's vitelliform macular degeneration

It is generally well accepted that in Best's vitelliform macular degeneration (BVMD) the electroretinogram (ERG) is normal whereas the electro-oculogram (EOG) is markedly abnormal. We describe a patient in whom BVMD was suspected on the basis of the clinical findings, EOG and family history (one of her daughters had the typical vitelliform lesion). However, her dark-adapted ERG was markedly abnormal. Similar anomalies were found in the dark-adapted ERG of the daughter. While the temporal features of the various ERG waves were well preserved, a substantial decrease in the amplitude of specific segments of the ERG signal was observed. A similar decrease in the amplitude of the oscillatory potentials was also found. We believe that this unusual combination of BVMD and abnormal dark-adapted ERG may be due to the reported reduced penetrance and variable expressivity of the BVMD gene(s).

Herpes zoster ophthalmoplegia. Report of six cases

Ophthalmoplegia occurs infrequently in herpes zoster ophthalmicus. The third nerve appears to be the most commonly affected and the fourth nerve the least. We describe herein the clinical course of six patients with herpes zoster ophthalmoplegia. Spontaneous recovery occurred in four patients. The pathogenesis and clinical features of this syndrome are described.

Postoperative vomiting following strabismus surgery in paediatric outpatients: spontaneous versus controlled ventilation

The study was designed to compare the frequency and severity of postoperative vomiting in paediatric out-patients receiving controlled ventilation (IPPV) or breathing spontaneously (SV) during anaesthesia for strabismus repair. One hundred and twenty unpremedicated children (ages 2-12 years) were studied in a randomized fashion. After intravenous induction of anaesthesia and tracheal intubation, patients breathed halothane 1-1.5 per cent inspired and N2O 66 per cent in O2 spontaneously (n = 60), or received IPPV, halothane 0.5-1 per cent, N2O 66 per cent, and pancuronium 0.05 mg.kg-1, which was reversed with neostigmine and atropine (n = 60). The incidence of vomiting with SV was 50 per cent (95 per cent confidence limits: 34.5-65.5 per cent) compared with 40 per cent (24.5-55.5 per cent) with IPPV (p greater than 0.25). Patients in the SV group experiencing emesis had longer operations than those not vomiting (mean +/- SEM = 1.5 +/- 0.1 vs 1.2 +/- 0.1 hours, p less than 0.005). This was not the case with IPPV. There was no correlation between age, sex, duration of surgery, or number of extraocular muscles repaired, and frequency or severity of vomiting or time to discharge. No significant advantage was afforded by IPPV over SV in the present study.

Autosomal recessive Duane's retraction syndrome

The first two cases of probable autosomal recessive Duane's retraction syndrome, in two siblings, are reported.

Nonhealing corneal defects due to herpes simplex in children

Two young children with unilateral photophobia, redness, blepharospasm and corneal epithelial defects unresponsive to conservative therapy were seen between December 1982 and June 1983. Herpes simplex virus was established as the causal agent in both cases, only after the children had been examined under general anesthesia and appropriate cultures obtained. The difficulties in diagnosing herpetic keratitis in children and the treatment and long-term prognosis are discussed.

Herpes simplex keratitis and amblyopia

Herpes simplex keratitis can cause severe loss of vision in children. The findings in five children show that amblyopia is caused by stimulus deprivation and/or anisometropia. Early medical treatment, occlusion therapy, and frequent refractions are crucial for a good visual prognosis.

Norrie's disease in a French-Canadian kindred: attempt to detect carriers by DNA analysis

In a French-Canadian kindred four male cousins are affected with Norrie's disease, a rare X-linked recessive disorder. Three have university education, and the fourth has some developmental delay. Only one is microcephalic. All have mild to severe hearing deficit, although only three were aware of their hearing loss. Linkage analysis of DNA from family members with the probe L1.28 failed to detect female carriers.

Traumatic disinsertion of the superior rectus

The authors report the findings and management of traumatic disinsertion of the superior rectus occurring in a 55-year-old woman.

The Okihiro syndrome of Duane anomaly, radial ray abnormalities, and deafness

We report on a child with Duane anomaly, deafness, cervical spine, and radial ray abnormalities. A sister of the proposita had hemifacial microsomia, cervical abnormalities, and hypoplasia of the thenar eminence. Four relatives had hypoplasia of the thenar eminence. A fifth had preaxial polydactyly. Duane anomaly was present in two sixth-degree relatives. This appears to be an autosomal dominant trait. Singly or in combination the abnormalities seen in this family have all been described in association with Duane anomaly. Their occurrence in the same family suggests that they are not independent entities but represent pleiotropic effects of the same gene.

Optic disc colobomas

This paper describes optic disc colobomas in a father and his twin sons. Two of the six eyes had associated anterior colobomas (one of the iris and the other of the peripheral retina), and there was evidence of abnormal development of Bergmeister's papilla in the father's left eye.

Further observations on the auditory brainstem response in Duane's syndrome

Auditory brainstem responses were recorded in 16 patients with Duane's syndrome. There were no significant differences in the mean wave and interwave latencies between the patients and 16 neurologically and audiologically normal control subjects, although 2 patients had responses from one side that were of increased latency. A consistent relation between the auditory brainstem response and the affected eye was not found; therefore, the data from this study do not support the findings of a previous report on this subject.

Waardenburg syndrome--penetrance of major signs

We have estimated that 83% of individuals carrying the gene for Waardenburg syndrome type I show penetrance of the gene as measured by dystopia canthorum. This is lower than previous estimates, which failed to consider the frequency of equivocal dystopia in the general population. The addition of three other major signs (hearing loss, white forelock, and premature graying of the hair or vitiligo) does not substantially increase the discrimination of gene carriers (85% versus 83%). We estimate that about 75% of the first-degree relatives of probands can be assigned as normal or a gene carrier on the basis of the four major signs.

The photopic electroretinogram in congenital stationary night blindness with myopia

Previous studies have reported that subjects affected with congenital stationary night blindness and myopia demonstrated some photopic (cone) abnormalities in their electroretinogram (ERG). By comparing the photopic ERG elicited with a threshold and a suprathreshold stimulus it was found that, at threshold, no significant differences were noted both in the peak time and in the amplitude of ERGs evoked from CSNB and normal subjects. However, a more powerful stimulus (16 times the threshold) yields a significant difference in the ERGs recorded from the two groups. ERGs recorded from CSNB patients are decreased in amplitude with a b-wave peak time that remains normal. First derivative analysis of the ERG wave along with a selective recording of the oscillatory components of the ERG suggest that the only visible anomaly in the suprathreshold photopic ERG of CSNB patients is an absence of the two oscillations normally seen on the ascending portion of the b-wave. Data obtained on normal subjects are also reported that try to explain the functional significance of these two oscillatory potentials.

Unilateral congenital ptosis and amblyopia

Amblyopia was detected in 15 of 55 children with unilateral congenital ptosis. Anisometropia was the main cause of the amblyopia in 10 cases, and strabismus alone was the cause in 2 cases. In three cases amblyopia developed after ptosis surgery.

Lenz microphthalmia: a malformation syndrome with variable expression of multiple congenital anomalies

Lenz microphthalmia is a syndrome of microphthalmia accompanied by multiple congenital anomalies, none of which is unique to the syndrome. The patient described in this paper had, in addition to the microphthalmia, dysmorphic facies and dental anomalies, several features not previously described in this syndrome: synophrys, an isolated cleft of the soft palate, a webbed neck and sacral pits. Other congenital syndromes associated with microphthalmia (oculodentodigital dysplasia, cryptophthalmos and the 10q+ syndrome) were excluded. The frequency of the anomalies described in 22 case reports is presented as a guide to diagnosis in isolated cases.

Ocular manifestations of Kawasaki disease (mucocutaneous lymph node syndrome)

This paper describes nine patients, five girls and four boys aged 4 months to 7 years (mean 3 3/4 years), who had the clinical and laboratory features of Kawasaki disease (mucocutaneous lymph node syndrome). Eight of them had mild to moderate anterior uveitis, and one child showed choroidal, retinal and vitreous changes in one eye that caused a severe visual loss. Recognition of this disease is important, particularly since 1% to 2% of patients under 2 years of age die suddenly from coronary arteritis.

Cataracts and ketotic hypoglycemia

Of 40 patients with ketotic hypoglycemia, 15 (nine boys and six girls) developed cataracts. The mean age at onset of the first hypoglycemic attack was 20 months, and the average age at the time the cataracts were discovered was 3 1/4 years. The average birth weight of 14 children was 2060 g. The cataracts were bilateral in all but one case. Seven patients (11 eyes, bilateral in four patients) developed complete cataracts. Despite aphakic correction and occlusion therapy, the major cause of visual loss after cataract surgery was stimulus deprivation amblyopia. Other ocular abnormalities included strabismus and jerky horizontal nystagmus. Neurologic impairment--epilepsy, psychomotor retardation, and/or electroencephalographic abnormalities--was present in over one half of the patients. All children with ketotic hypoglycemia should be referred promptly for an ophthalmic examination so that appropriate therapy can be implemented early.

Consecutive exotropia after correction of hyperopia

A study was done of 22 children in whom exotropia developed following correction of hyperopia because of accommodative esotropia that had not been corrected surgically. The early onset of esotropia and high degree of hyperopia seemed to predispose to the spontaneous development of exotropia. Reduction of the hyperopia by 50% to 60% resulted in satisfactory realignment of the eyes and some form of binocularity.

Ocular defects and short stature

The presence of ocular anomalies in a short child raises the possibility of hypothalamic-pituitary dysfunction or other intracranial abnormalities. The ocular, endocrine and neurologic findings in three children with short stature are described in this article. The first child had a large basal encephalocele, agenesis of the corpus callosum, mild optic atrophy in one eye, a retinal pigment epithelial defect in the other eye and bitemporal hemianopia; the second child had septo-optic dysplasia and the third child had Rieger's anomaly. All had deficient or abnormal growth hormone responses and two of the children had other pituitary hormonal abnormalities. It is suggested that an arrest of development during organogenesis can produce a spectrum of abnormalities involving ocular, endocrine and neurologic structures. Early diagnosis is important so that endocrinologic and neurologic investigations can be undertaken and appropriate therapy implemented.

Sandhoff's disease (GM2 gangliosidosis type 2). Histopathology and ultrastructure of the eye

Sandhoff's disease (GM2 gangliosidosis type 2) was diagnosed in an infant in whom a progressive neurologic disorder and cherry-red foveal spots developed. At autopsy, ultrastructural examination of the retina and optic nerve disclosed abundant pleomorphic storage cytosomes in all neurons of the retina, including the inner segments of the photoreceptor cells, and in glial cells of the optic nerve. Electron microscopy of the cornea showed, within the keratocytes, distended clear lysosomes that contained some fibrillogranular material and an occasional collection of lamellae. We discuss the pathogenesis of the clinical and pathologic ocular findings with regard to the inherited absence of the enzymes hexosaminidase A and B and an accumulation of the substrates, GM2 ganglioside and asialo GM2, in the nervous system (including retina and optic nerve) and globoside and other hexosamine-containing substances in the viscera (including cornea).

Total transient visual loss and orbital foreign bodies

Two children recovered vision after penetrating injury of the orbit by wood had produced sudden blindness. Absent light perception demands urgent action as early visual loss does not necessarily indicate a poor prognosis. The depth and direction of penetration and size of wooden fragments is difficult to assess clinically and radiologically. Immediate and delayed neurological complications should always be anticipated. Removal of all fragments of wood is of paramount importance in restoring visual acuity. Prolonged visual loss with symptoms and signs of retained foreign body demands vigorous management.

Congenital miosis

The inheritance of congenital miosis in 2 pedigrees is described. The inheritance was autosomal dominant in one and autosomal recessive in the other. The pupils were 0.5-2.5 mm diameter, reacted normally to light and accommodation but dilated poorly with mydriatics. In both pedigrees, the affected members had enlarged corneas. The five members in the autosomal dominant family were myopic and had translucent peripheral irides. Iridodonesis was presented in both members of the autosomal recessive pedigree. The embryology and innervation of the iris muscles together with the ocular abnormalities and syndromes associated with congenital miosis are reviewed.

Optic nerve in globoid leukodystrophy (Krabbe's disease). Ultrastructural changes

Globoid leukodystrophy (Krabbe's disease) was diagnosed in an infant in whom a progressive neurological disorder and optic atrophy developed. At autopsy, ultrastructural examination of the optic nerves and cerebral white matter revealed characteristic tubular inclusions in globoid-epithelioid cells. Thinning of the nerve fiber and ganglion cell layers of the retina appeared to be due to retrograde degeneration of the optic nerve related to the abnormal metabolism of myelin. We discuss the pathogenesis of the clinical and pathological ocular findings, with regard to the inherited absence of the enzyme galactocerebroside beta-galactosidase and the accumulation in the optic nerve and brain of its substrates, galactocerebroside and psychosine.

Stickler's syndrome (hereditary progressive arthro-ophthalmopathy)

The clinical features of Stickler's syndrome are described in two families with a total of 22 affected members and compared with those of the three previously reported families. Progressive joint degeneration (85%), myopia (83%) and retinal detachment (61%) are the most frequent manifestations. Cleft palate (28%), micrognathia (17%) and sensorineural hearing loss (9%) are also liable to occur in affected individuals. Inheritance is autosomal dominant with virtually complete penetrance. Genetic counselling is extremely important and relatively straightforward since most of the findings are manifest in the first two decades of life and represent severe incapacities to the affected families. All six of the affected individuals tested had increased urinary hydroxyproline excretion, a feature that may lead to earlier postnatal and possibly prenatal diagnosis.