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.

Heterozygous mutations of the kinesin KIF21A in congenital fibrosis of the extraocular muscles type 1 (CFEOM1)

Congenital fibrosis of the extraocular muscles type 1 (CFEOM1; OMIM #135700) is an autosomal dominant strabismus disorder associated with defects of the oculomotor nerve. We show that individuals with CFEOM1 harbor heterozygous missense mutations in a kinesin motor protein encoded by KIF21A. We identified six different mutations in 44 of 45 probands. The primary mutational hotspots are in the stalk domain, highlighting an important new role for KIF21A and its stalk in the formation of the oculomotor axis.

A Japanese family with FEOM1-linked congenital fibrosis of the extraocular muscles type 1 associated with spinal canal stenosis and refinement of the FEOM1 critical region

We identified a Japanese family with congenital fibrosis of the extraocular muscles, including 24 affected individuals through five generations. To determine their form of congenital fibrosis of the extraocular muscles, we performed clinical and linkage studies. DNA typing for linkage to the FEOM1 (12p11.2-q12) and FEOM3 (16qter) loci was performed on genomic DNA, using fluorescent microsatellite polymorphic markers. All affected individuals shared the common manifestations of congenital fibrosis of the extraocular muscles type 1 including congenital ptosis, infraducted globe position in primary gaze, and upward gaze palsy in both eyes. Unexpectedly, we found apparent spinal canal stenosis in the cervical spine in all affected family members who were examined. Genetic analysis revealed linkage to the FEOM1 locus with a maximum lod score of 4.42 at theta of zero. One affected family member harbored a recombination event between D12S345 and D12S1692, narrowing the FEOM1 locus from the published 3-cM region flanked by D12S1584 and D12S1668 to a 2.1-cM region flanked by D12S345 and D12S1668. Thus, we have established that this family segregates congenital fibrosis of the extraocular muscles type 1 as an autosomal dominant trait and that their disorder both maps to and refines the FEOM1 locus. This is the first clinical and genetic report of such a family in the Japanese population and the first report of spinal involvement in congenital fibrosis of the extraocular muscles.

Congenital fibrosis syndrome associated with central nervous system abnormalities

BACKGROUND

Congenital fibrosis of extraocular muscles (CFEOM) is a complex strabismus syndrome that typically occurs in isolation and results from dysfunction of all or part of cranial nerves III (CNIII) and IV (CNIV) and/or the muscles that these nerves innervate. Only a few patients with CFEOM and additional central nervous system malformations have been reported. We describe four additional patients with CFEOM associated with central nervous system (CNS) abnormalities.

METHODS

Four patients who presented with congenital restriction of eye movements in association with neurological abnormalities underwent complete ophthalmological examination including electroretinography (ERG) and eye movement recordings. Neurological examinations, neuroradiological studies, muscle histology, chromosomal and genetic linkage analysis were performed.

RESULTS

Clinical examination and forced duction testing confirmed that all four patients met criteria for CFEOM; all had congenital restrictive ophthalmoplegia primarily affecting extraocular muscles innervated by the oculomotor nerve. Two brothers had CFEOM and Marcus Gunn jaw winking. In each of the four cases, CFEOM occurred in association with one or several neuroradiological findings, including agenesis of the corpus callosum, colpocephaly, hypoplasia of the cerebellar vermis, expansion of the ventricular system, pachygyria, encephalocele and/or hydrancephaly.

CONCLUSIONS

We present four cases of CFEOM in association with CNS malformations that confirm that CFEOM can be part of a more complex neurological dysfunction and provide further support to a neurogenic aetiology for this disorder. We also describe for the first time the coexistence of CFEOM and Marcus Gunn jaw winking in two siblings. This suggests a genetic mechanism. Aberrant innervation supports primary developmental abnormality of cranial nerves in CFEOM.

Acute ataxia in childhood

Acute childhood ataxia is a common cause of presentation to the pediatric emergency room or child neurologist. The primary concern on initial assessment is to exclude serious causes of this clinical syndrome, including central nervous system infections and mass lesions, while recognizing the essentially benign nature of acute ataxia in most children. Childhood ataxia can be diagnostically approached by consideration of the temporal course and presence or absence of associated neurologic abnormalities. In all forms of childhood ataxia, outcome is largely determined by etiology. In this review, the various causes and syndromes of acute ataxia in childhood are described, with discussion of diagnostic considerations and an approach to investigation, treatment, and prognosis.

Hilaire C, Chan WM, Andrews C, McIntosh N, Nakano M, Martonyi EJ, Raymond WR, Okumura S, Okihiro MM, Engle EC. Duane radial ray syndrome (Okihiro syndrome) maps to 20q13 and results from mutations in SALL4, a new member of the SAL family

Duane syndrome is a congenital eye movement disorder characterized most typically by absence of abduction, restricted adduction, and retraction of the globe on attempted adduction. Duane syndrome can be coinherited with radial ray anomalies as an autosomal dominant trait, referred to as "Okihiro syndrome" or "Duane radial ray syndrome" (DRRS). We ascertained three pedigrees with DRRS and mapped their disease gene to a 21.6-cM region of chromosome 20 flanked by markers D20S888 and D20S102. A new member of the SAL family of proposed C(2)H(2) zinc finger transcription factors, SALL4, falls within the region. Mutation analysis of SALL4 in the three pedigrees revealed one nonsense and two frameshift heterozygous mutations. SALL4 represents the first identified Duane syndrome gene and the second malformation syndrome resulting from mutations in SAL genes and likely plays a critical role in abducens motoneuron development.

Familial unilateral Brown syndrome

PURPOSE

To report a family in which three siblings have unilateral late-onset Brown syndrome.

METHODS

The entire nuclear family underwent ophthalmologic evaluation. Orbital imaging and systemic workup were obtained to rule out local or systemic causes. Historic information was obtained from unavailable family members. The family's Brown syndrome trait was analyzed for linkage to the known congenital fibrosis syndrome loci and the CFEOM2 gene, ARIX, was sequenced in affected individuals.

RESULTS

All affected siblings developed left-sided Brown syndrome, worse on awakening, at 12-13 years of age. No evidence of Brown syndrome could be identified in other family members, either by exam or history. No abnormalities of the trochlear-tendon complex could be documented. Haplotype analysis of the Brown syndrome phenotype was consistent with recessive inheritance at the DURS1 locus and dominant inheritance with reduced penetrance at the DURS1, DURS2, and FEOM1 loci. No mutations were detected in CFEOM2 gene, ARIX.

CONCLUSIONS

We propose that a genetically determined predisposition to Brown syndrome is likely responsible for the observed manifestations in this family and that late age of onset and intermittent manifestations do not distinguish acquired from hereditary Brown syndrome. The pattern of inheritance of the Brown phenotype in this family could be either autosomal recessive or autosomal dominant with reduced penetrance. Our analysis only permitted the exclusion of the FEOM3 locus and the FEOM2 gene, ARIX. Future genetic studies of additional Brown syndrome families should shed additional light on the genetic basis of this disorder.

Elevation of one eye during tooth brushing

PURPOSE

To describe a patient with congenital fibrosis of the extraocular muscles (CFEOM) and elevation of one eye during tooth brushing.

METHODS

A 9-month-old girl underwent full ophthalmologic examination. Exonic and flanking intronic sequences of the CFEOM2 ARIX gene were sequenced.

RESULTS

The patient's clinical findings were consistent with classic CFEOM including chin elevation, bilateral ptosis, infraducted globes, no voluntary ocular elevation beyond midline, and convergence on attempted upgaze. During tooth brushing her right eye elevated beyond midline. This was elicited only by touching her teeth or gums but not by mouth movements. No ARIX mutations were detected.

CONCLUSION

This is the first case described with CFEOM and aberrant regeneration between the nerve to the superior rectus and the trigeminal nerve. This aberrant innervation supports a primary developmental abnormality of the cranial nerves in CFEOM.

The molecular basis of the congenital fibrosis syndromes

The congenital fibrosis syndromes (CFS) are rare inherited strabismus syndromes that present as congenital, nonprogressive ophthalmoplegias with active and passive restriction of globe movement, and include classic and atypical forms of congenital fibrosis of the extraocular muscles (CFEOM) and Duane syndrome (DS). Although historically believed to result from primary extraocular muscle fibrosis, both neuropathologic and genetic studies support the hypothesis that these disorders result from aberrant development of motor nuclei in the midbrain and pons.

Congenital fibrosis of the vertically acting extraocular muscles maps to the FEOM3 locus

The diagnosis of congenital fibrosis of the extraocular muscles (CFEOM) encompasses several different inherited strabismus syndromes characterized by congenital restrictive ophthalmoplegia affecting extraocular muscles innervated by the oculomotor and/or trochlear nerves. The OMIM database (http://www.ncbi.nlm.nih.gov/Omim/) currently contains four familial CFEOM phenotypes: CFEOM1-3, which map to the FEOM1-3 loci (MIM 135600, 602078, 604361), respectively, and congenital fibrosis of the vertically acting extraocular muscles (MIM 600638), reported in a single family without a corresponding genotype. We have had the opportunity to study the reported family with this fourth phenotype and now demonstrate that their phenotype can be reclassified as CFEOM3 and that it maps to FEOM3, flanked by D16S498 to 16qter, with a maximum lod score of 6.0.

Applications of molecular genetics to the understanding of congenital ocular motility disorders

The congenital fibrosis syndromes (CFS), including congenital fibrosis of the extraocular muscles (CFEOM) and Duane syndrome (DS), are rare congenital strabismus syndromes that present with nonprogressive restrictive ophthalmoplegia with or without ptosis. Although historically believed to result from primary extraocular muscle (EOM) fibrosis, our laboratory's work is based on the hypothesis that these disorders result from distinct, but analogous, developmental defects of the oculomotor (nIII), trochlear (nIV), and abducens (nVI) nuclei. We have defined three inherited CFEOM phenotypes (CFEOM1-3) and have mapped each phenotype to a distinct genetic locus (FEOM1-3). Individuals with CFEOM1 are born with bilateral ptosis and both eyes fixed in a downward position with absent upgaze and aberrant horizontal gaze. This disorder maps to the FEOM1 locus on chromosome 12cen.(1,2) Neuropathology studies of CFEOM1 reveal the absence of the superior division of oculomotor nerve and its corresponding alpha motor neurons in the midbrain, with abnormalities of target EOMs.(3) These neuropathology findings parallel those previously identified in Duane syndrome, in which there is an absence of nVI and the abducens nerve.(4,5) Individuals with CFEOM2 are born with bilateral ptosis and exotropia. This atypical form of CFEOM maps to the FEOM2 locus on chromosome 11q13 and results from mutations in ARIX (PHOX2A).(6,7) ARIX encodes a homeodomain transcription factor protein previously shown to be required for nIII/nIV development in mouse and zebrafish.(8,9) Together, these findings support the hypothesis that the congenital fibrosis syndromes result from parallel defects in nIII, nIV, and nVI nuclear development. Functional studies of the CFEOM genes should provide additional insight into the unique features of the extraocular lower motor neuron axis in health and disease. (For full (refs. 1-9), see reference list of the main paper.)

CFEOM1, the classic familial form of congenital fibrosis of the extraocular muscles, is genetically heterogeneous but does not result from mutations in ARIX

BACKGROUND

To learn about the molecular etiology of strabismus, we are studying the genetic basis of 'congenital fibrosis of the extraocular muscles' (CFEOM). These syndromes are characterized by congenital restrictive ophthalmoplegia affecting muscles in the oculomotor and trochlear nerve distribution. Individuals with the classic form of CFEOM are born with bilateral ptosis and infraducted globes. When all affected members of a family have classic CFEOM, we classify the family as a CFEOM1 pedigree. We have previously determined that a CFEOM1 gene maps to the FEOM1 locus on chromosome 12cen. We now identify additional pedigrees with CFEOM1 to determine if the disorder is genetically heterogeneous and, if so, if any affected members of CFEOM1 pedigrees or sporadic cases of classic CFEOM harbor mutations in ARIX, the CFEOM2 disease gene.

RESULTS

Eleven new CFEOM1 pedigrees were identified. All demonstrated autosomal dominant inheritance, and nine were consistent with linkage to FEOM1. Two small CFEOM1 families were not linked to FEOM1, and both were consistent with linkage to FEOM3. We screened two CFEOM1 families consistent with linkage to FEOM2 and 5 sporadic individuals with classic CFEOM and did not detect ARIX mutations.

CONCLUSIONS

The phenotype of two small CFEOM1 families does not map to FEOM1, establishing genetic heterogeneity for this disorder. These two families may harbor mutations in the FEOM3 gene, as their phenotype is consistent with linkage to this locus. Thus far, we have not identified ARIX mutations in any affected members of CFEOM1 pedigrees or in any sporadic cases of classic CFEOM.

Homozygous mutations in ARIX(PHOX2A) result in congenital fibrosis of the extraocular muscles type 2

Isolated strabismus affects 1-5% of the general population. Most forms of strabismus are multifactorial in origin; although there is probably an inherited component, the genetics of these disorders remain unclear. The congenital fibrosis syndromes (CFS) represent a subset of monogenic isolated strabismic disorders that are characterized by restrictive ophthalmoplegia, and include congenital fibrosis of the extraocular muscles (CFEOM) and Duane syndrome (DURS). Neuropathologic studies indicate that these disorders may result from the maldevelopment of the oculomotor (nIII), trochlear (nIV) and abducens (nVI) cranial nerve nuclei. To date, five CFS loci have been mapped (FEOM1, FEOM2, FEOM3, DURS1 and DURS2), but no genes have been identified. Here, we report three mutations in ARIX (also known as PHOX2A) in four CFEOM2 pedigrees. ARIX encodes a homeodomain transcription factor protein previously shown to be required for nIII/nIV development in mouse and zebrafish. Two of the mutations are predicted to disrupt splicing, whereas the third alters an amino acid within the conserved brachyury-like domain. These findings confirm the hypothesis that CFEOM2 results from the abnormal development of nIII/nIV (ref. 7) and emphasize a critical role for ARIX in the development of these midbrain motor nuclei.

Congenital fibrosis of the extraocular muscles associated with cortical dysplasia and maldevelopment of the basal ganglia

BACKGROUND

Congenital fibrosis of the extraocular muscles (CFEOM) is a rare condition that has been traditionally regarded as a primary eye muscle disease. Recent studies, however, suggest that CFEOM may be the result of a primary neuropathy with secondary myopathic changes.

PURPOSE

To describe a previously unrecognized association between congenital fibrosis of the extraocular muscles and structural abnormalities of the brain.

DESIGN

Small case series.

METHODS

Detailed clinical examinations and neuroradiologic studies were performed on the three affected family members. In addition, genetic analysis of the family was performed.

RESULTS

The three affected family members, mother and two children, have the ocular features of 'classic' congenital fibrosis of the extraocular muscles. All showed dilation of the left lateral ventricle secondary to hypoplasia of the body and tail of the ipsilateral caudate nucleus. There was fusion of an enlarged caudate nucleus head with the underlying putamen. Both children showed widespread bilateral cortical dysplasia. Genetic analysis of the family was inconclusive but consistent with linkage to the CFEOM1 locus on chromosome 12. Chromosomal analysis of the affected individuals did not show evidence of a deletion of chromosome 12 and haplotype analysis was not suggestive of a microdeletion.

CONCLUSIONS

Cerebral cortical and basal ganglia maldevelopment can be found in individuals with CFEOM. This suggests that neuroimaging should be considered in the initial diagnostic evaluation of these patients, particularly if there is developmental delay.

Analysis of human sarcospan as a candidate gene for CFEOM1

BACKGROUND

Congenital fibrosis of the extraocular muscles type 1 (CFEOM1) is an autosomal dominant eye movement disorder linked to the pericentromere of chromosome 12 (12p11.2 - q12). Sarcospan is a member of the dystrophin associated protein complex in skeletal and extraocular muscle and maps to human chromosome 12p11.2. Mutations in the genes encoding each of the other components of the skeletal muscle sarcospan-sarcoglycan complex (alpha - delta sarcoglycan) have been shown to cause limb girdle muscular dystrophy (LGMD2C-F). To determine whether mutations in the sarcospan gene are responsible for CFEOM1 we: (1) attempted to map sarcospan to the CFEOM1 critical region; (2) developed a genomic primer set to directly sequence the sarcospan gene in CFEOM1 patients; and (3) generated an anti-sarcospan antibody to examine extraocular muscle biopsies from CFEOM1 patients.

RESULTS

When tested by polymerase chain reaction, sarcospan sequence was not detected on yeast or bacterial artificial chromosomes from the CFEOM1 critical region. Sequencing of the sarcospan gene in CFEOM1 patients from 6 families revealed no mutations. Immunohistochemical studies of CFEOM1 extraocular muscles showed normal levels of sarcospan at the membrane. Finally, sarcospan was electronically mapped to bacterial artificial chromosomes that are considered to be outside of the CFEOM1 critical region.

CONCLUSIONS

In this report we evaluate sarcospan as a candidate gene for CFEOM1. We have found that it is highly unlikely that sarcospan is involved in the pathogenesis of this disease. As of yet no sarcospan gene mutations have been found to cause muscular abnormalities.

A clinically variant fibrosis syndrome in a Turkish family maps to the CFEOM1 locus on chromosome 12

OBJECTIVES

To describe the phenotype of a Turkish family with variably expressed congenital fibrosis of the extraocular muscles (CFEOM), and to determine the genetic location of their disorder.

METHODS

Participants were examined and had blood extracted for genetic analysis. The clinical features of the family's disorder were studied, and the disorder was tested for linkage to the 3 known CFEOM loci (CFEOM1, CFEOM2, and CFEOM3).

RESULTS

Twenty-nine affected and 31 unaffected family members participated in the study. Eighteen affected individuals had congenital bilateral ptosis and restrictive infraductive (downward) ophthalmoplegia, consistent with the published descriptions of classic CFEOM families linked to the CFEOM1 locus. Eleven affected individuals, however, had eye(s) in a neutral primary position, residual upgaze, and/or absence of ptosis, thus deviating from previous descriptions of CFEOM1-linked families. Analysis of the autosomal dominant variably expressed disorder in this family revealed linkage to the CFEOM1 locus on chromosome 12 with a maximum lod score of 10.8 at D12S85.

CONCLUSIONS

This Turkish family segregates a variably expressed form of CFEOM that most closely resembles CFEOM3-linked CFEOM, but maps to the CFEOM1 locus.

CLINICAL RELEVANCE

These data establish that there is much greater phenotypic heterogeneity at the CFEOM1 locus than previously reported, and this may blur our ability to distinguish the different CFEOM loci based solely on clinical presentation. Arch Ophthalmol. 2000;118:1090-1097

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.

CFEOM3: a new extraocular congenital fibrosis syndrome that maps to 16q24.2-q24.3

PURPOSE

To define the clinical characteristics and determine the gene localization for a previously undescribed form of congenital fibrosis of the extraocular muscles (CFEOM), referred to as CFEOM type 3 (CFEOM3).

METHODS

A large family with CFEOM was identified, and participating individuals underwent ophthalmologic examination and donated blood for genetic analysis. The family's disorder was tested for linkage to the known CFEOM loci, followed by a genome-wide search and linkage refinement using polymorphic DNA markers.

RESULTS

Thirty-eight members of this Canadian family participated in the study. Affected individuals are born with a nonprogressive eye movement disorder characterized by variable expression of ptosis and restrictive external ophthalmoplegia. Severely affected individuals have ptosis, primary gaze fixed in a hypo- and exotropic position, and marked restriction of eye movement bilaterally. Mildly affected individuals have normally positioned globes with a limitation of vertical gaze. Moderately affected individuals have asymmetrical involvement with one eye severely and one eye mildly affected. The disorder is autosomal dominant with variable expression and probable incomplete penetrance. Genetic analysis reveals linkage to markers on 16q24.2q24.3. A maximum lod score of 5.8 occurs at markers D16S3063 and D16S689, and the CFEOM3 disease gene is located within a 5.6-cM region flanked by D16S486 and D16S671.

CONCLUSIONS

These data establish that CFEOM3 is a phenotypically variant and genotypically distinct form of CFEOM with linkage to chromosome 16qter. The authors have previously demonstrated that CFEOM1 results from a developmental absence of the superior division of the oculomotor nerve. The authors hypothesize that CFEOM3 results from a defect analogous to, but distinct from CFEOM1.

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.

Mutilating hand syndrome in an infant with familial carpal tunnel syndrome

A 7-month-old infant, son of consanguinous Indian parents, presented with recurrent chewing of his digits in a median nerve distribution as the primary manifestation of carpal tunnel syndrome, in conjunction with features consistent with congenital insensitivity to pain. Electromyography (EMG) demonstrated severe median nerve entrapment at the wrist bilaterally, but other nerves were normal. In spite of clinical evidence of diffuse pain insensitivity, sural nerve and skin biopsies were normal, and he had no evidence of autonomic dysfunction. Hand findings evolved with scarring and infection of median innervated digits and loss of fine motor skills. Carpal tunnel release resulted in complete clinical resolution and significant EMG improvement. Milder symptoms and EMG evidence of median nerve entrapment were demonstrated in both parents, paternal grandparents, and several of his father's siblings. We hypothesize this child may be homozygous for a mutant allele that in its heterozygous state predisposes to familial autosomal dominant carpal tunnel syndrome. Homozygosity for this or another mutant allele may be responsible for his congenital insensitivity to pain.

A gene for isolated congenital ptosis maps to a 3-cM region within 1p32-p34.1

Hereditary isolated congenital ptosis is an autosomal dominant disorder with incomplete penetrance characterized by a variable degree of unilateral or bilateral drooping of the upper eyelids. We report linkage of this disorder in a large family to markers on chromosome 1p. In our sample of 37 meioses, nine informative markers did not recombine with the disease. D1S2677 gave a maximum two-point LOD score of 8.8 on the assumption of 90% penetrance (theta = 0). D1S447/2733 and D1S1616 flank the disease locus, with two-point LOD scores of 5.6/6.6 (theta = .04) and 4.9 (theta = .05), respectively, defining a region of 2.8 cM. FISH of YACs containing flanking recombinant markers localizes the gene to chromosome 1p32-p34.1. These data establish a map location for an isolated congenital ptosis gene and demonstrate that this disorder is genetically distinct from other extraocular muscle-specific disorders such as congenital fibrosis of the extraocular muscles and blepharophimosis.

Oculomotor nerve and muscle abnormalities in congenital fibrosis of the extraocular muscles

Congenital fibrosis of the extraocular muscles is an autosomal dominant congenital disorder characterized by bilateral ptosis, restrictive external ophthalmoplegia with the eyes partially or completely fixed in an infraducted (downward) and strabismic position, and markedly limited and aberrant residual eye movements. It has been generally thought that these clinical abnormalities result from myopathic fibrosis of the extraocular muscles. We describe the intracranial and orbital pathology of 1 and the muscle pathology of 2 other affected members of a family with chromosome 12-linked congenital fibrosis of the extraocular muscles. There is an absence of the superior division of the oculomotor nerve and its corresponding alpha motor neurons, and abnormalities of the levator palpebrae superioris and rectus superior (the muscles innervated by the superior division of the oculomotor nerve). In addition, increased numbers of internal nuclei and central mitochondrial clumping are found in other extraocular muscles, suggesting that the muscle pathology extends beyond the muscles innervated by the superior division of cranial nerve III. This report presents evidence that congenital fibrosis of the extraocular muscles results from an abnormality in the development of the extraocular muscle lower motor neuron system.