The causal effect of obesity on concomitant exotropia: A lifecourse Mendelian randomization study

Obesity is now a significant global public health issue. Limited understanding exists regarding the association between obesity and concomitant exotropia. Our objective was to identify the causal relationship between lifecourse obesity, including birth weight, childhood body mass index (BMI), and adult BMI, and the risk of concomitant exotropia. We used a two-sample Mendelian randomization (MR) strategy to examine the causal relationship with inverse-variance weighted method as the primary MR analysis. We carried out sensitivity analyses to evaluate the accuracy and robustness of our findings. Also, we performed reverse-direction MR analysis to eliminate the possibility of reverse causality. Childhood BMI, as opposed to birth weight or adult BMI, had a significant impact on the risk of concomitant exotropia (odds ratio = 1.40, 95% confidence interval (CI): 1.08-1.81, P = .01). This significance persisted even after accounting for birth weight and adult BMI using multivariable MR analysis (odds ratio = 1.35, 95% CI: 1.04-1.75, P = .02). There was no significant heterogeneity or pleiotropy observed in sensitivity analyses (P > .05). Multivariable MR analysis further confirmed the absence of pleiotropic effects of some risk factors including prematurity, maternal smoking around birth and refractive error. Reverse causality did not affect the causal relationship (beta = -0.0244, 95% CI: -0.0545 to 0.0056, P = .11). Genetic predisposition to higher childhood BMI was found to be causally linked to an increased risk of concomitant exotropia.

Special clinical features with a novel mutation site of CHN1 gene in a Chinese family with Duane retraction syndrome

PURPOSE

This study is to describe the special clinical and genotypic features of a Chinese family with variant types of Duane retraction syndrome and to present our experience on managing these cases.

METHODS

Four individuals from one family were reviewed by ophthalmologic examinations, in which two affected and two unaffected individuals were revealed. MRI scans were performed on the two patients. Relevant gene mutations were screened by the next-generation sequencing technology and confirmed by Sanger sequencing technology.

RESULTS

The six-year-old proband presented with special clinical features of severe horizontal gaze dysfunction, exotropia and mild scoliosis. His mother showed significantly limited binocular abductions, with retraction of eyeballs in adduction. From MRI scans, abducens nerves were not observed in both patients and the oculomotor nerve was slightly thin in the proband. The proband and his mother shared the same CHN1 gene mutation site (c. 62A>G; p.Y21C). Strabismus surgery was performed on the proband to correct the primary gaze exotropia.(NM_001822: exon3 or NM_001025201: exon4: c. 62A>G; p.Y21C).

CONCLUSIONS

A novel CHN1 gene mutation was revealed from a Chinese family with Duane retraction syndrome. Remarkably, the proband and his mother presented different clinical features of ocular motility disorder. Strabismus correction surgery and amblyopia training helped to improve the appearance and visual function of the proband.

Presence of Copy Number Variants Associated With Esotropia in Patients With Exotropia

Importance

Strabismus is a common ocular disorder of childhood. There is a clear genetic component to strabismus, but it is not known if esotropia and exotropia share genetic risk factors.

Objective

To determine whether genetic duplications associated with esotropia are also associated with exotropia.

Design, Setting, and Participants

This was a cross-sectional study conducted from November 2005 to December 2023. Individuals with constant or intermittent exotropia of any magnitude or a history of surgery for exotropia were recruited from pediatric ophthalmic practices. Data were analyzed from March to December 2023.

Exposure

Genetic duplication.

Main Outcomes and Measures

Presence of genetic duplications at 2p11.2, 4p15.2, and 10q11.22 assessed by digital droplet polymerase chain reaction. Orthoptic measurements and history of strabismus surgery were performed.

Results

A total of 234 individuals (mean [SD] age, 19.5 [19.0] years; 127 female [54.3%]) were included in this study. The chromosome 2 duplication was present in 1.7% of patients with exotropia (4 of 234; P = .40), a similar proportion to the 1.4% of patients with esotropia (23 of 1614) in whom it was previously reported and higher than the 0.1% of controls (4 of 3922) previously reported (difference, 1.6%; 95% CI, 0%-3.3%; P < .001). The chromosome 4 duplication was present in 3.0% of patients with exotropia (7 of 234; P = .10), a similar proportion to the 1.7% of patients with esotropia (27 of 1614) and higher than the 0.2% of controls (6 of 3922) in whom it was previously reported (difference, 2.8%; 95% CI, 0.6%-5.0%; P < .001). The chromosome 10 duplication was present in 6.0% of patients with exotropia (14 of 234; P = .08), a similar proportion to the 4% of patients with esotropia (64 of 1614) and higher than the 0.4% of controls (18 of 3922) in whom it was previously reported (difference, 5.6%; 95% CI, 2.5%-8.6%; P < .001). Individuals with a duplication had higher mean (SD) magnitude of deviation (31 [13] vs 22 [14] prism diopters [PD]; difference, 9 PD; 95% CI, 1-16 PD; P = .03), were more likely to have constant (vs intermittent) exotropia (70% vs 29%; difference, 41%; 95% CI, 20.8%-61.2%; P < .001), and had a higher rate of exotropia surgery than those without a duplication (58% vs 34%; difference, 24%; 95% CI, 3%-44%; P = .02).

Conclusions and Relevance

In this cross-sectional study, results suggest that the genetic duplications on chromosomes 2, 4, and 10 were risk factors for exotropia as well as esotropia. These findings support the possibility that esotropia and exotropia have shared genetic risk factors. Whether esotropia or exotropia develops in the presence of these duplications may be influenced by other shared or independent genetic variants or by environmental factors.

Association of IGF1 polymorphisms with exotropia in a Pakistani cohort

PURPOSE

Strabismus (STBMS) is a multifactorial ocular disorder in children that leads to misalignment of the eyes. Insulin-like growth factor 1 (IGF1) has been shown to be involved in the development of extraocular muscles and myopia; however, data are limited on the genetic associations of IGF1 with STBMS in Pakistan.

METHODS

Two hundred seventy-four STBMS cases and 272 unaffected controls were recruited, and their DNA was extracted. Two IGF1 single nucleotide polymorphisms, rs6214 and rs5742632, were genotyped using PCR-restriction fragment length polymorphism. Univariate logistic regression analysis was performed to determine the association of these single nucleotide polymorphisms with STBMS, and the results were adjusted for age and sex. In addition, 26 extraocular muscle tissues were collected from patients with STBMS undergoing squint correction surgery, along with 3 deceased control samples. IGF1 mRNA expression was measured by quantitative PCR; the Mann-Whitney U test was applied, and fold change was calculated. Logistic regression analysis was applied to determine the association of RNA expression and fold change with genotype.

RESULTS

Multivariate logistic regression analysis revealed that rs5742632 (odds ratio [95% confidence interval] = 1.05[1.01-1.06], p = 0.03) is associated with STBM. Moreover, rs6214 (1.03[1.01-1.05], p = 0.03) and rs5742632 (1.09[1.04-1.11], p = 0.04) were associated with exotropia. Statistically, no significant difference in IGF1 mRNA expression in the extraocular muscles between the STBMS cases and the controls was observed.

CONCLUSIONS

IGF1 polymorphisms rs5742632 (A>G) and rs6214 (C>T) are plausible risk factors for the development of exotropia. However, the physiologic mechanism requires further evaluation.

Ocular findings in Gillespie-like syndrome: association with a new PAX6 mutation

BACKGROUND

Gillespie syndrome is a rare variant form of aniridia, characterized by mental retardation, nonprogressive cerebellar ataxia, and iris hypoplasia. Unlike the more common dominant and sporadic forms of aniridia, there have been no associated PAX6 mutations or Wilms' tumor reported in Gillespie syndrome patients. Ocular findings in 21 cases published since Gillespie's initial description in 1965 include iris and foveal hypoplasia, nystagmus, and small optic discs with pigmentary retinopathy.

CASE REPORT

We herein report a case of atypical Gillespie syndrome associated with bilateral ptosis, exotropia, corectopia, iris hypoplasia, anterior capsular lens opacities, foveal hypoplasia, retinal vascular tortuosity, and retinal hypopigmentation. Neurologic evaluation revealed a mild hand tremor and learning disability, but no ataxia or cerebellar abnormalities on neuroimaging. Sequencing studies revealed a substitution in intron 2 of the PAX6 gene (IVS2 + 2T > A). To our knowledge, this is the first mutation of PAX6 gene reported in association with a Gillespie-like syndrome.

Neurological features of congenital fibrosis of the extraocular muscles type 2 with mutations in PHOX2A

Congenital fibrosis of the extraocular muscles type 2 (CFEOM2) is a complex strabismus syndrome that results from mutations in the homeodomain transcription factor PHOX2A. To define the clinical and neuroimaging features of patients with this autosomal recessive syndrome, we studied 15 patients with genetically defined CFEOM2. All patients underwent full neurological, neuro-ophthalmological and orthoptic assessments. Twelve patients had pupillary pharmacological testing and nine had 3.0 tesla MRI of the brain, brainstem and orbits. Patients were born with severe bilateral ptosis and exotropia with almost complete bilateral absence of adduction, elevation, depression and intorsion. Variable abduction was present prior to strabismus surgery in 14 patients, and central ocular motility reflexes (smooth pursuit, saccades, vestibulo-ocular reflex and optokinetic reflex) were intact except for convergence. Pupillary light and near reflexes were not present, but irises were anatomically normal and responded to pupillary pharmacology. Neuroimaging of brain and brainstem was remarkable for the anatomical absence of cranial nerve (CN) 3 and probably CN 4 bilaterally. Therefore, the CFEOM2 phenotype and neuroimaging are both consistent with the congenital absence of CNs 3 and 4. Additional features included presence of most central ocular motility reflexes, a central lack of pupillary responsiveness of uncertain aetiology and modest phenotypic variability that does not correlate with specific PHOX2A mutations. Clinical presentation, neuroimaging and Phox2a-/- animal models all support the concept that CFEOM2 is a primary neurogenic abnormality with secondary myopathic changes.

[Ocular findings in patients with Steinert myotonic dystrophy]

The authors present one of many myotonic dystrophies: Steinert myotonic dystrophy (Steinert disease), which is a disease occuring seldom, and causing a lot of problems during the diagnostic and treatment process. Genetic factors, results of the histopathology tests, main clinical symptoms, particularly ophtalmic manifestation are described in this article.

Symmetrical bilateral lens colobomas in two brothers

True lens coloboma is a rare developmental disorder usually caused by missing lens zonules in the equatorial area of the lens. Bilateral cases are rare. We report bilateral superonasal lens colobomas in two brothers whose parents are first cousins.

[Schizophrenia and ocular misalignment: phenotypic and genetic association analysis]

The increased incidence of minor physical anomalies (MPAs) in schizophrenia is the fundamental basis for the neurodevelopmental hypothesis of schizophrenia etiology. Ocular misalignment falls into the category of MPAs, but this phenotype has not been assessed in schizophrenia. This study reveals that constant exotropia displays marked association with schizophrenia. To assess the genetic mechanisms, we examined the transcription factor genes ARIX and its paralogue, PMX2B. We identified frequent deletion/insertion polymorphisms in the 20-alanine homopolymer stretch of PMX2B, with a modest association between these functional polymorphisms and constant exotropia in schizophrenia. The polymorphisms were also associated with overall schizophrenia and more specifically with schizophrenia manifesting strabismus. These results suggest a possible interaction between PMX2B and other schizophrenia-precipitating factors, increasing the risk of the combined phenotypes. This study also highlights the unique nature of the polyalanine length variations found in PMX2B.

A novel PHOX2A/ARIX mutation in an Iranian family with congenital fibrosis of extraocular muscles type 2 (CFEOM2)

PURPOSE

To describe the clinical features of two affected members of an Iranian family with autosomal recessive congenital fibrosis of the extraocular muscles (CFEOM2) and to report their novel mutation in the PHOX2A/ARIX gene.

DESIGN

Experimental study.

METHODS

SETTING

Institutional practice. patient population:Six members of an Iranian family with CFEOM underwent complete ocular examinations including assessment of ocular motility, visual acuity, slit-lamp biomicroscopy, tonometry, and ophthalmoscopy.

EXPERIMENTAL PROCEDURE

Mutation analysis of the PHOX2A gene was performed using polymerase chain reaction amplification of the coding exons and direct sequencing of polymerase chain reaction products.

MAIN OUTCOME MEASURE

Presence or absence of mutation in PHOX2A gene in two siblings with exotropia and recessive CFEOM. Exotropia and ptosis were corrected surgically in one of the two siblings.

RESULTS

The two affected siblings had bilateral ptosis and exotropia and severe limitation of all extraocular movements. One patient underwent strabismus surgery and ptosis repair. PHOX2A mutation analysis revealed a novel nonsense mutation in exon 2 (439C-->T). Both parents and the unaffected siblings were heterozygous,and the two affected siblings were homozygous for this mutation.

CONCLUSIONS

The 439C-->T mutation in this family changes a glutamine to a stop codon (Q90X) at the beginning of the PHOX2A homeodomain region. This is the fourth CFEOM2 mutation in PHOX2A and the first nonsense mutation to be identified. It confirms PHOX2A as the autosomal recessive CFEOM2 disease gene and provides evidence that the phenotypic differences between PHOX2A mutations in man and mouse do not result from hypomorphic PHOX2A alleles in humans.

Clinical features of comitant strabismus related to family history of strabismus or abnormalities in pregnancy and delivery

PURPOSE

To elucidate the genetic or environmental background for clinical features in the three major types of comitant strabismus.

METHODS

Interview based on a questionnaire asking background factors such as family history of strabismus and abnormalities in pregnancy and delivery was conducted with 101 consecutive patients with infantile esotropia (5-180 months of age), 83 with accommodative or partially accommodative esotropia (6-201 months of age), and 143 with intermittent exotropia (3-216 months of age) seen during 7 months from May to November 1998. The clinical features of strabismus obtained from medical records were analyzed statistically by logistic regression to determine their relation with these background factors.

RESULTS

In infantile esotropia, patients with family history of strabismus had a significantly higher chance of showing latent nystagmus (odds ratio, 3.553; 95% confidence interval [CI], 1.077-11.717; P =.0373, logistic regression analysis). In a subgroup of 40 patients with infantile esotropia whose birth followed no abnormalities in pregnancy or delivery, patients with family history of strabismus had a significantly higher chance of showing inferior oblique muscle overaction (odds ratio, 7.714; 95% CI, 1.246-47.761; P =.0280), dissociated vertical deviation (odds ratio, 6.667; 95% CI, 1.176-37.787; P =.0321), and latent nystagmus (odds ratio, 7.333; 95% CI, 1.168-46.060; P =.0336). In accommodative or partially accommodative esotropia and intermittent exotropia, no relation was found between the clinical features and the background factors.

CONCLUSIONS

Inferior oblique muscle overaction, dissociated vertical deviation, and latent nystagmus in infantile esotropia might have a genetic background.

A study of heredity as a risk factor in strabismus

AIMS

Inheritance is recognised to have a part in the aetiology of strabismus but previous studies have not adequately distinguished between different types of strabismus leading to wide variations in reported findings. The aim of this study was to investigate the importance of heredity in different types of strabismus.

METHODS

The parents of children attending for treatment of strabismus over a one-month period were interviewed to identify relatives with a history of strabismus. A complete three-generation pedigree was established for 96 index cases who were classified into four groups: infantile esotropia (26 cases), accommodative esotropia (49 cases), anisometropic esotropia (15 cases), and exotropia (six cases).

RESULTS

Forty-three of a total of 165 (26.1%) first degree relatives of patients with hypermetropic accommodative esotropia were affected. In contrast, 15 of a total of 101 (14.9%) first degree relatives of patients with infantile esotropia, eight of a total of 66 (12.1%) first degree relatives of patients with anisometropic esotropia, and one of a total of 25 (4%) first degree relatives of patients with exotropia were affected. Analysing the data using logistic regression with a random term for family showed a significantly higher proportion of affected first degree relatives in the accommodative group than in any of the other three diagnostic groups.

CONCLUSION

A history of strabismus appears to be more common in hypermetropic accommodative esotropia than in infantile esotropia, anisometropic esotropia or exotropia. More detailed investigation of the role of heredity in the aetiology of accommodative esotropia is needed.

[Hereditary factors in strabismus]

This retrospective study took place in the Ophthalmology Department of Douala General Hospital. The aim was to determine the importance of hereditary factors in a group of strabismic Cameroonians. In a series of 275 patients with strabismus, we found 79 familial cases (28.72%). Among them, 22.78% had more than one relative with squint and 75% had the same type of strabismus as their relative. There was no significant difference in the percentage of familial cases with regard to the type of strabismus, the sex, the mode of fixation and the impairment of ductions. As far as ametropias are concerned, only myopia showed a hereditary tendency in our series. The authors agree with the literature in that there is a significant hereditary component in the cause of strabismus, but its genetic sites are yet to be identified. There is strong hope in this direction with the decoding of the human genom and the advances in molecular biology. However, the study of familial cases is important since it allows high risk groups to be defined and screened. It thus makes it possible to successfully fight amblyopia through early detection and treatment.

[Maculopathy in Curschmann-Steinert myotonic dystrophy]

BACKGROUND

Maculopathy occurring in young patients is a challenge in differential diagnosis. Besides hereditary macular dystrophies and acquired macular degenerations, rare systemic disorders should be considered.

CASE REPORT

A 36 year old female patient complained about a gradually decrease of visual acuity in both eyes and an increasing exotropia of her right eye. Visual acuity was 0.7, the orthoptical status revealed an intermittent exophoria with exclusion of the right eye. Slit lamp examination showed punctate and cristalline lens opacities. In fundus examination and fluorescein angiography clumpy pigment epithelium hypertrophies and atrophies with a reticular character could be observed. Color vision and perimetry were normal; dark visual acuity was reduced. Because of remarkable deformations of jaw and teeth, a high hairline and an uncertain step we arranged a neurological consultation. Clinical observation together with myotonic activities in electromyography and diffuse lesions in the cerebral medular corpus shown in MRT led to the diagnosis of myotonic dystrophy (Curschmann Steinert syndrome).

CONCLUSION

Besides hereditary macular dystrophies and acquired macular degenerations the differential diagnosis of maculopathies in young patients also includes systemic disorders. Myotonic dystrophy (Curschmann Steinert syndrome) should be taken into account as a rare cause of a juvenile maculopathy.

Incontinentia pigmenti (Bloch-Sulzberger-syndrome): case report and differential diagnosisto related dermato-ocular syndromes

BACKGROUND

Incontinentia pigmenti (IP; Bloch-Sulzberger syndrome) is an inherited disorder of skin pigmentation that is associated with skin (100%), dental (90%), skeletal (40%), central nervous (40%) and ocular (35%) abnormalities. The pathogenesis is not yet known. The disease is usually seen in females, as it is an X-linked dominantly inherited disease which is lethal in males.

PATIENT PRESENTATION

We present a 9-year-old girl with the classical general and ocular signs of IP. She presented in early childhood with inflammatory vesicular skin changes which changed into pigmented skin alterations especially on the trunk. Ocular findings were microphthalmia and retrolental mass formation in one eye and retinal pigmentary changes in the other. In our patient, the spontaneous mutation may have been caused by the family's close neighbourhood to Semipalatinsk, Kasachstan, where regular nuclear tests took place very shortly before the pregnancy with our patient began.

DISCUSSION

Ocular involvement is described in about a third of persons affected with IP. A nearly consistent and pathognomonic finding is a pigment retinopathy (mottled diffuse hypopigmentations). A further consistent finding are abnormalities of peripheral retinal vessels with areas of non-perfusion in the outer retina. The retinal pigment epitheliopathy and the abnormalities of retinal vessels are thought to be the underlying pathognomonic findings, with all other ocular signs being secondary (cataract, leucocoria, optic atrophy, strabismus, nystagmus and microphthalmus). Exudative retinal detachment occurs only in a minority, usually in very early childhood, when the skin lesions are exudative as well. IP patients should, however, be clinically observed regularly because of their retinal pigmentary changes.

Evidence of genetic heterogeneity in autosomal recessive congenital fibrosis of the extraocular muscles

PURPOSE

Autosomal recessive congenital fibrosis of the extraocular muscles (CFEOM2) has been described in families from Saudi Arabia. Affected individuals have ptosis and exotropic ophthalmoplegia, and their disease has been mapped to chromosome 11q13. Here, we describe the phenotypic findings in a similarly affected Yemenite family and analyze the family for linkage to the CFEOM2 locus, as well as to the autosomal dominant CFEOM1 and CFEOM3 loci on chromosomes 12cen and 16q24, respectively.

METHODS

The family was ascertained through two affected daughters. There are four unaffected siblings, and the parents are consanguineous. Each family member was examined, and linkage analysis was performed using markers from the CFEOM1, CFEOM2, and CFEOM3 loci.

RESULTS

Both affected daughters have congenital bilateral ophthalmoplegia. The 15-month-old proband has restrictive exotropia. She fixates with either eye in abduction and with a compensatory head turn to the opposite side. Her 4-year-old sister has a small exotropia and severely limited eye movements. All other family members have normal ophthalmologic examinations. Genetic analysis excluded linkage of the family's disease to the CFEOM2 and CFEOM3 loci. A lod score of 2.0 (the maximum possible, given the family size and structure), was obtained at the CFEOM1 locus, and the alleles reduced to homozygosity in both affected daughters and none of the other children.

CONCLUSIONS

These data establish that there is genetic heterogeneity in autosomal recessive CFEOM and suggest that this second recessive locus may be allelic to the autosomal dominant CFEOM1 locus at 12cen.

[Exotropia in black Cameroonians]

We carried out this study to increase our knowledge and understanding of exotropia (divergent strabismus) in general, but particularly in black people, in whom it occurs more frequently. We carried out a prospective study in the department of ophthalmology of Douala General Hospital from November 1991 to June 1998. All patients underwent oculomotor examination and skiascopye. In a series of 225 consecutive strabismus cases, we identified 147 cases of exotropia (59.51%) in 67 male patients (45.58%) and 80 female patients (54.42%). In 59.86% of these cases, exotropia was evident before the age of one year and 59.19% had amblyopia. The mean age at first examination was 17.04 years (+/- 12.12 years). Hyperopia was the most common form of ametropia (59.86%) and 39 patients (26.53%) had parents, children or siblings who also had exotropia. We found that exotropia was the most common form of strabismus in black people in Cameroon and that it spontaneously progressed to amblyopia in a significant number of cases. We therefore recommend early, active treatment.

Clinical characteristics of CHARGE syndrome

CHARGE syndrome, first described by Pagon, was named for its six major clinical features. They are: coloboma of the eye, heart defects, atresia of the choanae, retarded growth and development including CNS anomalies, genital hypoplasia and/or urinary tract anomalies, and ear anomalies and/or hearing loss. We experienced three cases of CHARGE syndrome who displayed ocular coloboma, heart defects, retarded growth and development, and external ear anomalies, and we also review the previously reported literature concerning CHARGE syndrome.

Congenital fibrosis of the extraocular muscles type 2, an inherited exotropic strabismus fixus, maps to distal 11q13

The extraocular fibrosis syndromes are congenital ocular-motility disorders that arise from dysfunction of the oculomotor, trochlear, and abducens nerves and/or the muscles that they innervate. Each is marked by a specific form of restrictive paralytic ophthalmoplegia with or without ptosis. Individuals with the classic form of congenital fibrosis of the extraocular muscles (CFEOM1) are born with bilateral ptosis and a restrictive infraductive external ophthalmoplegia. We previously demonstrated that CFEOM1 is caused by an autosomal dominant locus on chromosome 12 and results from a developmental absence of the superior division of the oculomotor nerve. We now have mapped a variant of CFEOM, exotropic strabismus fixus ("CFEOM2"). Affected individuals are born with bilateral ptosis and restrictive ophthalmoplegia with the globes "frozen" in extreme abduction. This autosomal recessive disorder is present in members of three consanguineous Saudi Arabian families. Genetic analysis of 70 individuals (20 affected individuals) reveals linkage to markers on chromosome 11q13, with a combined LOD score of 12.3 at the single nonrecombinant marker, D11S1314. The 2.5-cM CFEOM2 critical region is flanked by D11S4196/D11S4162 and D11S4184/1369. Two of the three families share a common disease-associated haplotype, suggesting a founder effect for CFEOM2. We hypothesize that CFEOM2 results from an analogous developmental defect to CFEOM1, one that affects both the superior and inferior divisions of the oculomotor nerve and their corresponding alpha motoneurons and extraocular muscles.

Most Jacobsen syndrome deletion breakpoints occur distal to FRA11B

Recent studies have identified a (CCG)n repeat in the 5' untranslated region of the CBL2 protooncogene (11q23.3) and have demonstrated that expansion of this repeat causes expression of the folate-sensitive fragile site FRA11B. It has also been demonstrated that FRA11B is the site of breakage in some cases of Jacobsen syndrome (JS) involving terminal deletions of chromosome 11q. We report on 2 patients with JS and a 46,XX,del(11)(q23.3) karyotype. In both cases, microsatellite and fluorescence in situ hybridization analyses indicated that the deletion breakpoint was approximately 1.5-3 Mb telomeric to FRA11B. There was no evidence of expansion of the CBL2 (CCG)n repeat in the parents of either patient. The deleted chromosome was of paternal origin in both cases, although it was of maternal origin in the cases reported to be caused by FRA11B. These findings and those in previously reported patients suggest that the breakpoint for most 11q deletions in JS patients is telomeric to FRA11B, which raises the possibility that there may be other fragile sites in 11q23.3 in addition to FRA11B. These findings also support previous evidence that there may be a propensity for breakpoints to differ depending on the parental origin of the deleted chromosome.

Associations between siblings for esotropia and exotropia

OBJECTIVE

To quantify familial aggregation of esotropia and exotropia in children examined in a large multicenter study.

METHODS

Pregnant women and their children were examined in the Collaborative Perinatal Project of the National Institute of Neurological Disorders and Stroke, Bethesda, Md. Strabismus was evaluated in the children during follow-up examinations up to the age of 7 years. The second-order generalized estimating equations approach to logistic regression was used to estimate familial aggregation of esotropia and exotropia.

RESULTS

For any pair of siblings, the odds for one sibling having esotropia more than doubled when the other sibling had esotropia. For exotropia, there were differences in sibling associations based on birth relationships. In particular, there was no statistically significant association between siblings from separate single births. On the other hand, for the pairs of siblings from multiple births (ie, twins, triplets, and quadruplets), the odds for exotropia in one sibling were increased by at least a factor of 17 when the other sibling from that birth also had exotropia. For both esotropia and exotropia, adjustment for previously identified risk factors only somewhat reduced the magnitudes of the observed associations. Limited data on zygosity showed a stronger association between monozygotic twins than between dizygotic twins.

CONCLUSIONS

There is a significant familial component in the cause of strabismus. Furthermore, there are important contributions to this familial aggregation beyond those associated with known risk factors for strabismus.

[An unusual eye defect in Highland cattle: diverging unilateral strabismus]

In the course of an investigation on breeding, management, health and economic problems in seven Highland Cattle farms, two castrated (male) full sibs were detected showing divergent unilateral strabismus (DUS). The reason being found for this eye-defect was a displacement of the M. rectus lateralis by 40 degrees to ventral. Besides DUS, both full sibs were affected by crop ears. It seems probable that DUS is an inborn defect, but the pedigree was not so informative that conclusions on the inheritance of DUS could be drawn.

Unique X-linked mental retardation syndrome with fingertip arches and contractures linked to Xq21.31

We studied 10 members of a 4 generation Missouri kindred with a dominant mental retardation syndrome with increasing severity in males. The 21 year-old propositus presented with severe mental retardation, microcephaly, asymmetric face, exotropia, hypogonadism, joint hypermobility, rocker bottom feet, and 10 low digital arches. Two brothers and a male cousin had similar features. The mother, sister, niece, maternal aunt, female cousin, and grandmother were examined and each had 8 to 10 low digital arches. Five of the women had exotropia and one had pes cavus feet. Chromosome analysis for fragile X in multiple relatives was normal. To determine the likelihood that this was an X-linked syndrome. DNA from relatives was hybridized to probes which detect 13 different loci spanning the X-chromosome. A peak LOD score of 2.78 at theta equal to 0.0 was calculated for the syndrome locus and DXYS1 (pDP34). The more distal Xq loci showed increasing recombination with the syndrome locus. These results are consistent with location for this syndrome near Xq21.31, the chromosomal locus for DXYSI.

Familial Brown's syndrome

We present findings in two siblings with bilateral Brown's syndrome and review other reported familial cases.