Micro syndrome in Muslim Pakistan children

From cataract to syndrome diagnosis: Revaluation of Warburg-Micro syndrome Type 1 patients

Warburg-Micro syndrome (WARBM) is a rare autosomal recessively inherited neuro-ophthalmologic syndrome. Although WARBM shows genetic heterogeneity, the pathogenic variants in RAB3GAP1 were the most common cause of WARBM. In this study, we aimed to evaluate the detailed clinical and dysmorphic features of seven WARBM1 patients and overview the variant spectrum of RAB3GAP1 in comparison with the literature who were referred due to congenital cataracts. A previously reported homozygous variant (c.2187_2188delGAinsCT) was identified in three of these patients, while the other four had three novel variants (c.251_258delAGAA, c.2606+1G>A, and c.2861_2862dupGC). Congenital cataract and corpus callosum hypo/agenesia are pathognomonic for WARBM, which could be distinguished from other similar syndromes with additional typical dysmorphic facial features. Although there is no known phenotype and genotype correlation in any type of WARBM, RAB3GAP1 gene analysis should be previously requested as the first step of genetic diagnosis in clinically suspicious patients when it is not possible to request a multi-gene panel.

Rab18 Collaborates with Rab7 to Modulate Lysosomal and Autophagy Activities in the Nervous System: an Overlapping Mechanism for Warburg Micro Syndrome and Charcot-Marie-Tooth Neuropathy Type 2B

Mutations in RAB18, a member of small G protein, cause Warburg micro syndrome (WARBM), whose clinical features include vision impairment, postnatal microcephaly, and lower limb spasticity. Previously, our Rab18^-/- mice exhibited hind limb weakness and spasticity as well as signs of axonal degeneration in the spinal cord and lumbar spinal nerves. However, the cellular and molecular function of RAB18 and its roles in the pathogenesis of WARBM are still not fully understood. Using immunofluorescence staining and expression of Rab18 and organelle markers, we find that Rab18 associates with lysosomes and actively traffics along neurites in cultured neurons. Interestingly, Rab18^-/- neurons exhibit impaired lysosomal transport. Using autophagosome marker LC3-II, we show that Rab18 dysfunction leads to aberrant autophagy activities in neurons. Electron microscopy further reveals accumulation of lipofuscin-like granules in the dorsal root ganglion of Rab18^-/- mice. Surprisingly, Rab18 colocalizes, cofractionates, and coprecipitates with the lysosomal regulator Rab7, mutations of which cause Charcot-Marie-Tooth (CMT) neuropathy type 2B. Moreover, Rab7 is upregulated in Rab18-deficient neurons, suggesting a compensatory effect. Together, our results suggest that the functions of RAB18 and RAB7 in lysosomal and autophagic activities may constitute an overlapping mechanism underlying WARBM and CMT pathogenesis in the nervous system.

The association of RAB18 gene polymorphism (rs3765133) with cerebellar volume in healthy adults

Genetic factors are responsible for the development of the human brain. Certain genetic factors are known to increase the risk of common brain disorders and affect the brain structure. Therefore, even in healthy people, these factors have a role in the development of specific brain regions. Loss-of-function mutations in the RAB18 gene (RAB18) cause Warburg Micro syndrome, which is associated with reduced brain size and deformed brain structures. In this study, we hypothesized that the RAB18 variant might influence regional brain volumes in healthy people. The study participants comprised 246 normal volunteers between 21 and 59 years of age (mean age of 37.8 ± 12.0 years; 115 men, 131 women). Magnetic resonance imaging (MRI) and genotypes of RAB18 rs3765133 were examined for each participant. The differences in regional brain volumes between T homozygotes and A-allele carriers were tested using voxel-based morphometry. The results showed that RAB18 rs3765133 T homozygote group exhibited larger gray matter (GM) volume in the left middle temporal and inferior frontal gyrus of the cerebrum than the A-allele carriers. An opposite effect was observed in both the posterior lobes and right tonsil of the cerebellum, in which the GM volume of RAB18 rs3765133 T homozygotes was smaller than that of the A-allele carriers (all P FWE < 0.05). Our findings suggest that RAB18 rs3765133 polymorphism affects the deve-lopment of specific brain regions, particularly the cerebellum, in healthy people.

Targeted disruption of Tbc1d20 with zinc-finger nucleases causes cataracts and testicular abnormalities in mice

Background

Loss-of-function mutations in TBC1D20 cause Warburg Micro syndrome 4 (WARBM4), which is an autosomal recessive syndromic disorder characterized by eye, brain, and genital abnormalities. Blind sterile (bs) mice carry a Tbc1d20-null mutation and exhibit cataracts and testicular phenotypes similar to those observed in WARBM4 patients. In addition to TBC1D20, mutations in RAB3GAP1, RAB3GAP2 and RAB18 cause WARBM1-3 respectively. However, regardless of which gene harbors the causative mutation, all individuals affected with WARBM exhibit indistinguishable clinical presentations. In contrast, bs, Rab3gap1^-/-, and Rab18^-/- mice exhibit distinct phenotypes; this phenotypic variability of WARBM mice was previously attributed to potential compensatory mechanisms. Rab3gap1^-/- and Rab18^-/- mice were genetically engineered using standard approaches, whereas the Tbc1d20 mutation in the bs mice arose spontaneously. There is the possibility that another unidentified mutation within the bs linkage disequilibrium may be contributing to the bs phenotypes and thus contributing to the phenotypic variability in WARBM mice. The goal of this study was to establish the phenotypic consequences in mice caused by the disruption of the Tbc1d20 gene.

Results

The zinc finger nuclease (ZFN) mediated genomic editing generated a Tbc1d20 c.[418_426del] deletion encoding a putative TBC1D20-ZFN protein with an in-frame p.[H140_Y143del] deletion within the highly conserved TBC domain. The evaluation of Tbc1d20^ZFN/ZFN eyes identified severe cataracts and thickened pupillary sphincter muscle. Tbc1d20^ZFN/ZFN males are infertile and the analysis of the seminiferous tubules identified disrupted acrosomal development. The compound heterozygote Tbc1d20^ZFN/bs mice, generated from an allelic bs/+ X Tbc1d20^ZFN/+ cross, exhibited cataracts and aberrant acrosomal development indicating a failure to complement.

Conclusions

Our findings show that the disruption of Tbc1d20 in mice results in cataracts and aberrant acrosomal formation, thus establishing bs and Tbc1d20^ZFN/ZFN as allelic variants. Although the WARBM molecular disease etiology remains unclear, both the bs and Tbc1d20^ZFN/ZFN mice are excellent model organisms for future studies to establish TBC1D20-mediated molecular and cellular functions.

Loss-of-function mutations in TBC1D20 cause cataracts and male infertility in blind sterile mice and Warburg micro syndrome in humans

blind sterile (bs) is a spontaneous autosomal-recessive mouse mutation discovered more than 30 years ago. Phenotypically, bs mice exhibit nuclear cataracts and male infertility; genetic analyses assigned the bs locus to mouse chromosome 2. In this study, we first positionally cloned the bs locus and identified a putative causative mutation in the Tbc1d20 gene. Functional analysis established the mouse TBC1D20 protein as a GTPase-activating protein (GAP) for RAB1 and RAB2, and bs as a TBC1D20 loss-of-function mutation. Evaluation of bs mouse embryonic fibroblasts (mEFs) identified enlarged Golgi morphology and aberrant lipid droplet (LD) formation. Based on the function of TBC1D20 as a RABGAP and the bs cataract and testicular phenotypes, we hypothesized that mutations in TBC1D20 may contribute to Warburg micro syndrome (WARBM); WARBM constitutes a spectrum of disorders characterized by eye, brain, and endocrine abnormalities caused by mutations in RAB3GAP1, RAB3GAP2, and RAB18. Sequence analysis of a cohort of 77 families affected by WARBM identified five distinct TBC1D20 loss-of-function mutations, thereby establishing these mutations as causative of WARBM. Evaluation of human fibroblasts deficient in TBC1D20 function identified aberrant LDs similar to those identified in the bs mEFs. Additionally, our results show that human fibroblasts deficient in RAB18 and RAB3GAP1 function also exhibit aberrant LD formation. These findings collectively indicate that a defect in LD formation/metabolism may be a common cellular abnormality associated with WARBM, although it remains unclear whether abnormalities in LD metabolism are contributing to WARBM disease pathology.

Mutation spectrum in RAB3GAP1, RAB3GAP2, and RAB18 and genotype-phenotype correlations in warburg micro syndrome and Martsolf syndrome

Warburg Micro syndrome and Martsolf syndrome (MS) are heterogeneous autosomal-recessive developmental disorders characterized by brain, eye, and endocrine abnormalities. Causative biallelic germline mutations have been identified in RAB3GAP1, RAB3GAP2, or RAB18, each of which encode proteins involved in membrane trafficking. This report provides an up to date overview of all known disease variants identified in 29 previously published families and 52 new families. One-hundred and forty-four Micro and nine Martsolf families were investigated, identifying mutations in RAB3GAP1 in 41% of cases, mutations in RAB3GAP2 in 7% of cases, and mutations in RAB18 in 5% of cases. These are listed in Leiden Open source Variation Databases, which was created by us for all three genes. Genotype-phenotype correlations for these genes have now established that the clinical phenotypes in Micro syndrome and MS represent a phenotypic continuum related to the nature and severity of the mutations present in the disease genes, with more deleterious mutations causing Micro syndrome and milder mutations causing MS. RAB18 has not yet been linked to the RAB3 pathways, but mutations in all three genes cause an indistinguishable phenotype, making it likely that there is some overlap. There is considerable genetic heterogeneity for these disorders and further gene identification will help delineate these pathways.

Loss-of-function mutations in RAB18 cause Warburg micro syndrome

Warburg Micro syndrome and Martsolf syndrome are heterogenous autosomal-recessive developmental disorders characterized by brain, eye, and endocrine abnormalities. Previously, identification of mutations in RAB3GAP1 and RAB3GAP2 in both these syndromes implicated dysregulation of the RAB3 cycle (which controls calcium-mediated exocytosis of neurotransmitters and hormones) in disease pathogenesis. RAB3GAP1 and RAB3GAP2 encode the catalytic and noncatalytic subunits of the hetrodimeric enzyme RAB3GAP (RAB3GTPase-activating protein), a key regulator of the RAB3 cycle. We performed autozygosity mapping in five consanguineous families without RAB3GAP1/2 mutations and identified loss-of-function mutations in RAB18. A c.71T > A (p.Leu24Gln) founder mutation was identified in four Pakistani families, and a homozygous exon 2 deletion (predicted to result in a frameshift) was found in the fifth family. A single family whose members were compound heterozygotes for an anti-termination mutation of the stop codon c.619T > C (p.X207QextX20) and an inframe arginine deletion c.277_279 del (p.Arg93 del) were identified after direct gene sequencing and multiplex ligation-dependent probe amplification (MLPA) of a further 58 families. Nucleotide binding assays for RAB18(Leu24Gln) and RAB18(Arg93del) showed that these mutant proteins were functionally null in that they were unable to bind guanine. The clinical features of Warburg Micro syndrome patients with RAB3GAP1 or RAB3GAP2 mutations and RAB18 mutations are indistinguishable, although the role of RAB18 in trafficking is still emerging, and it has not been linked previously to the RAB3 pathway. Knockdown of rab18 in zebrafish suggests that it might have a conserved developmental role. Our findings imply that RAB18 has a critical role in human brain and eye development and neurodegeneration.

New RAB3GAP1 mutations in patients with Warburg Micro Syndrome from different ethnic backgrounds and a possible founder effect in the Danish

Warburg Micro Syndrome is a rare, autosomal recessive syndrome characterized by microcephaly, microphthalmia, microcornia, congenital cataracts, optic atrophy, cortical dysplasia, in particular corpus callosum hypoplasia, severe mental retardation, spastic diplegia, and hypogonadism. We have found five new mutations in the RAB3GAP1 gene in seven patients with suspected Micro Syndrome from families with Turkish, Palestinian, Danish, and Guatemalan backgrounds. A thorough clinical investigation of the patients has allowed the delineation of symptoms that are consistently present in the patients and may aid the differential diagnosis of Micro Syndrome for patients in the future. All patients had postnatal microcephaly, micropthalmia, microcornia, bilateral congenital cataracts, short palpebral fissures, optic atrophy, severe mental retardation, and congenital hypotonia with subsequent spasticity. Only one patient had microcephaly at birth, highlighting the fact that congenital microcephaly is not a consistent feature of Micro syndrome. Analysis of the brain magnetic resonance imagings (MRIs) revealed a consistent pattern of polymicrogyria in the frontal and parietal lobes, wide sylvian fissures, a thin hypoplastic corpus callosum, and increased subdural spaces. All patients were homozygous for the mutations detected and all mutations were predicted to result in a truncated RAB3GAP1 protein. The analysis of nine polymorphic markers flanking the RAB3GAP1 gene showed that the mutation c.1410C>A (p.Tyr470X), for which a Danish patient was homozygous, occurred on a haplotype that is shared by the unrelated heterozygous parents of the patient. This suggests a possible founder effect for this mutation in the Danish population.

Warburg Micro syndrome in a Turkish boy

We report a 4-year-old Turkish boy with Warburg Micro syndrome born to consanguineous parents. He had ptosis, deep-set eyes, microphthalmia, microcornea, microcephaly, prominent ears and nasal root, micrognathia, hypertrichosis, spastic diplegia, skin hyperextensibility and joint hypermobility, hypogenitalism, cerebral atrophy and hypoplasia of corpus callosum and cerebellum. Sequence analysis of exon 8 of the RAB3GAP gene has confirmed the presence of a splice donor mutation (748+1G>A) in the homozygous state. Skin hyperextensibility and joint hypermobility in the affected child have not been reported in Warburg Micro syndrome cases to date. This report compares the symptoms and features of the case with previously reported cases of Warburg Micro syndrome.

Martsolf syndrome in Japanese siblings

We describe a Japanese brother and sister with Martsolf syndrome. They had short stature, severe mental retardation, cataract, hypogonadism, craniofacial dysmorphism, and bone and joint symptoms including scoliosis, lax finger joints, and talipes valgus. Previously undescribed findings included proximal femoral epiphyseal dysplasia reminiscent of Legg-Calve-Perthes disease in both patients, and Klippel-Feil malformation and osteopathia striata in one patient. Brain MRI showed mild frontal and temporal lobe atrophy, and mild ventricular enlargement. Severe GH deficiency was demonstrated after insulin tolerance and glucagon/propranolol tolerance tests. No responses to serum LH and FSH after a gonadotropin-releasing hormone (GnRH) test suggested secondary hypogonadism, that is, hypogonadotropic hypogonadism, due to hypothalamus-pituitary axis insufficiency in both patients.

Uveal coloboma: clinical and basic science update

PURPOSE OF REVIEW

To integrate knowledge on the embryologic and molecular basis of optic fissure closure with clinical observations in patients with uveal coloboma.

RECENT FINDINGS

Closure of the optic fissure has been well characterized and many genetic alterations have been associated with coloboma; however, molecular mechanisms leading to coloboma remain largely unknown. In the past decade, we have gained better understanding of genes critical to eye development; however, mutations in these genes have been found in few individuals with coloboma. CHD7 mutations have been identified in patients with CHARGE syndrome (coloboma, heart defects, choanal atresia, retarded growth, genital anomalies, and ear anomalies or deafness). Animal models are bringing us closer to a molecular understanding of optic fissure closure.

SUMMARY

Optic fissure closure requires precise orchestration in timing and apposition of two poles of the optic cup. The relative roles of genetics and environment on this process remain elusive. While most cases of coloboma are sporadic, autosomal dominant, autosomal recessive, and X-linked inheritance patterns have been described. Genetically, colobomata demonstrate pleiotropy, heterogeneity, variable expressivity, and reduced penetrance. Coloboma is a complex disorder with a variable prognosis and requires regular examination to optimize visual acuity and to monitor for potential complications.

Mutation in Rab3 GTPase-activating protein (RAB3GAP) noncatalytic subunit in a kindred with Martsolf syndrome

We identified a homozygous missense mutation in the noncatalytic subunit (RAB3GAP2) of RAB3GAP that results in abnormal splicing in a family with congenital cataracts, hypogonadism, and mild mental retardation (Martsolf syndrome). Recently, mutations in the catalytic subunit of RAB3GAP (RAB3GAP1), a key regulator of calcium-mediated hormone and neurotransmitter exocytosis, were reported in Warburg micro syndrome, a severe neurodevelopmental condition with overlapping clinical features. RAB3GAP is a heterodimeric protein that consists of a catalytic subunit and a noncatalytic subunit encoded by RAB3GAP1 and RAB3GAP2, respectively. We performed messenger RNA-expression studies of RAB3GAP1 and RAB3GAP2 orthologues in Danio rerio embryos and demonstrated that, whereas developmental expression of rab3gap1 was generalized (similar to that reported elsewhere in mice), rab3gap2 expression was restricted to the central nervous system. These findings are consistent with RAB3GAP2 having a key role in neurodevelopment and may indicate that Warburg micro and Martsolf syndromes represent a spectrum of disorders. However, we did not detect RAB3GAP2 mutations in patients with Warburg micro syndrome. These findings suggest that RAB3GAP dysregulation may result in a spectrum of phenotypes that range from Warburg micro syndrome to Martsolf syndrome.

Microphthalmia and brain atrophy: A novel neurodegenerative disease

OBJECTIVE

To delineate the features of a novel neurodegenerative disease.

METHODS

We report three children of three related families with congenital microphthalmia and blindness, and progressive spasticity, microcephaly, seizures, and profound mental retardation.

RESULTS

A magnetic resonance imaging scan was normal at birth. However, follow-up studies showed progressive atrophy involving the cerebral white matter and cortex, cerebellum, brainstem, and corpus callosum. The white matter changes extended into the subcortical region leaving only small islands of remaining cortical tissue. Known metabolic conditions involving white matter degeneration were excluded.

INTERPRETATION

We propose this to be a novel autosomal recessive neurodegenerative disorder to be coined MOBA (microphthalmia brain atrophy) disease.

Mutations of the catalytic subunit of RAB3GAP cause Warburg Micro syndrome

Warburg Micro syndrome (WARBM1) is a severe autosomal recessive disorder characterized by developmental abnormalities of the eye and central nervous system and by microgenitalia. We identified homozygous inactivating mutations in RAB3GAP, encoding RAB3 GTPase activating protein, a key regulator of the Rab3 pathway implicated in exocytic release of neurotransmitters and hormones, in 12 families with Micro syndrome. We hypothesize that the underlying pathogenesis of Micro syndrome is a failure of exocytic release of ocular and neurodevelopmental trophic factors.

MICRO syndrome: an entity distinct from COFS syndrome

Children born with the findings of microcephaly, cataracts and microcornea can result not only from a prenatal viral infection, but also from an autosomal recessive Mendelian disorders. We present three pairs of affected siblings with MICRO syndrome, who were born with congenital microcephaly, microcornea, and cataracts. MICRO syndrome is an autosomal recessive syndrome consisting of congenital microcephaly, cortical dysplasia, microcornea, cataracts, optic atrophy, severe mental retardation, hypotonic diplegia, and hypogenitalism. At birth, MICRO syndrome resembles Cerebro-Oculo-Facio-Skeletal (COFS) syndrome, but it differs in the lack of the rapidly progressive neurologic features leading to severe brain atrophy with calcifications. Patients with MICRO syndrome manifest frontal cortical dysplasia, hypoplasia of the corpus callosum, cortical blindness with optic atrophy, profound mental retardation, and progressive joint contractures with growth failure. COFS syndrome shares also many clinical and cellular similarities with Cockayne syndrome (CS), and cultured cells in both conditions demonstrate hypersensitivity to ultraviolet (UV) radiation due to impaired nucleotide excision repair (NER). NER studies in cultured fibroblasts from MICRO patients give normal results, so MICRO syndrome should be considered in children with features resembling COFS syndrome and CS, but who have normal NER. MICRO should be distinguished from other similar clinical disorders with normal NER by the presence of significant visual impairment and cortical blindness despite early surgery for congenital cataracts, frontal polymicrogyria, thin corpus callosum, and cortical atrophy by MRI.

Congenital cataract, microphthalmia, hypoplasia of corpus callosum and hypogenitalism: report and review of Micro syndrome

We report on a 7-month-old boy with Micro syndrome who was referred for assessment of mental-motor retardation and reduced vision with cataract. The characteristics of Micro syndrome are mental retardation, microcephaly, congenital cataract, microcornea, microphthalmia, agenesis/hypoplasia of the corpus callosum, and hypogenitalism. The differential diagnosis includes cerebro-oculo-facio-skeletal syndrome (COFS); a syndrome involving cataract, arthrogryposis, microcephaly, and kyphoscoliosis (CAMAK); a syndrome with cataract, microcephaly, failure to thrive, and kyphoscoliosis (CAMFAK); Martsolf syndrome; Neu-Laxova syndrome; Lenz microphthalmia syndrome; and Smith-Lemli-Opitz syndrome. Till date, no renal malformations have been reported in Micro syndrome. Our patient had fusion of the lower poles of the kidneys and his left kidney was ectopic. Ocular findings are the most reliable neonatal diagnostic signs of Micro syndrome. Minör anomalies in Micro syndrome may be subtle and therefore not of significant diagnostic value. Micro syndrome is an autosomal recessive trait. Till date, most reported cases have been in individuals of Muslim origin. In countries with high rates of consanguineous marriage, such as Turkey, it is important that physicians be able to recognize this syndrome. Micro syndrome should be considered in any infant with congenital cataract.

Ocular features of the congenital cataracts facial dysmorphism neuropathy syndrome

OBJECTIVE

To determine the nature and course of ophthalmologic abnormalities in congenital cataracts facial dysmorphism neuropathy (CCFDN) syndrome in a genetically verified group of 9 patients.

STUDY DESIGN

Observational case series.

PARTICIPANTS

Nine affected male individuals of 5 pedigrees aged 1.3 to 16.8 years were examined. Four individuals were recruited during an ongoing prospective study of congenital cataracts; 5 individuals could be assigned to the CCFDN group on the basis of our retrospective data.

MAIN OUTCOME MEASURES

Linkage and haplotype analysis, neurologic examinations, bilateral cataracts, axial length, corneal diameter, pupil diameter and pupillary reactions, intraoperative and postoperative complications, lid changes, aphakic correction problems, refractive results, and visual function.

RESULTS

All families originated from the eastern part of Serbia, close to the border with Romania. The 8 tested individuals were homozygous for the conserved ancestral CCFDN haplotype in the telomeric region of chromosome 18q. All patients showed a peripheral, demyelinating neuropathy and varying degrees of ataxia. In the older patients, muscular atrophy in distal muscles and facial dysmorphism was evident. Early-onset bilateral congenital cataracts associated with microcornea, microphthalmos, and micropupil could be found in all patients. All children had floppy eyelid syndrome and pseudoptosis. An increased inflammatory reaction to contact lenses and intraocular lenses could be documented in all. All patients had syndrome-associated nystagmus and congenital esotropia. Distant visual acuity could be classified as severe to moderate impairment, whereas near visual acuity was much better (mild to moderate impairment).

CONCLUSIONS

Early-onset congenital cataracts associated with microcornea, microphthalmos, and micropupil are essential ocular features of the CCFDN syndrome and are the first recognizable signs during early infancy. Awareness of this syndrome by pediatric ophthalmologists is important, because these typical findings, combined with information on ethnic origin, may lead to very early diagnosis at an age when the nature and severity of nonophthalmologic features are not apparent. Affected individuals may benefit from careful ophthalmologic treatment and follow-up, as well as from early management of the neurologic problems and developmental delay. Affected families will benefit from genetic counseling and predictive testing.

Genotypic and phenotypic heterogeneity in familial microcoria

AIMS

To describe the clinical features and genetic findings in two families presenting with microcoria inherited as an autosomal dominant trait.

METHODS

Both affected and unaffected members of two families displaying familial microcoria were examined. Flash photography or infrared pupillography were used to assess pupils, and a full ophthalmic examination including visual acuity and field testing, refraction, biomicroscopy of anterior and posterior segments, and measurement of intraocular pressure were performed. DNA from the blood of affected and unaffected family members was investigated using standard markers to look for a possible gene defect in the chromosome 13q31-q32 region.

RESULTS

All affected members of both families had pinpoint pupils which responded normally to light and accommodation. None of these subjects exhibited any other ocular abnormality. The iris of affected members showed stromal thinning and apparent absence of the iris dilator muscle in the first family, but was smooth and lacked all trabecular structure in the second family. The microcoria was present at birth in the first family but developed progressively at a later age in the second family. Haplotype analysis suggested the gene defect is not located in the chromosome 13q31-q32 region in the first family but the evidence was not conclusive in the second family.

CONCLUSION

Although both families presented with similar pupil abnormalities inherited as an autosomal dominant trait, they show important phenotypic and genotypic differences suggesting that this is a heterogeneous condition. The possible mechanisms underlying the microcoria are discussed.

Value of electrodiagnostic assessment in nonsyndromic microcephaly

PURPOSE

To evaluate the value of electroretinogram (ERG) and visual evoked potentials (VEP) in children with nonsyndromic microcephaly.

METHODS

In this observational case series, six children with nonsyndromic microcephaly aged 8.5 to 158 months were examined. Main outcome measures included the amplitude of the flash ERG (photopic, flickering, scotopic, and dark-adapted responses), the amplitude and latency of the VEP (flash or pattern-reversal stimulus), visual acuity, slit-lamp biomicroscopy, and indirect ophthalmoscopy.

RESULTS

Three children demonstrated normal fundus appearances, ERG, and VEP responses: two in this group demonstrated poor vision and brain computed tomography in the third showed schizencephaly. The remaining three children demonstrated abnormal ERG with predominant reduction in photopic amplitudes. Retinal pigmentary granularities were detected in two children in this group, one of whom has poor vision, generalized brain atrophy, and 40% reduction in VEP amplitudes.

CONCLUSIONS

Abnormal ERG is not uncommon among children with nonsyndromic microcephaly. Although cone photoreceptors are affected more than rods, this does not anticipate poor vision. It appears that defects in posterior visual pathway or developmental malformations of the brain should be responsible for poor visual function in nonsyndromic microcephaly.

Autopsy case of multiple anomalies with hypoplastic cerebrum, eyes, and endocrine organs, mimicking Micro syndrome

We report an autopsy case of multiple anomalies with severe micrencephaly, bilateral microphthalmos, and hypoplastic endocrine organs. We examined expressions of calcium-binding proteins and hypothalamic and pituitary hormones. A female proband presented with microcephaly, microphthalmia, and psychomotor development delay. At the age of 23 years, she died of cardiorespiratory failure. The endocrine organs demonstrated severe underdevelopment, and the hypoplastic eyeballs had remnant lens, vitreous hemorrhage, and retinal detachment. The brain weighed 260 g; the cerebrum, cerebellum, and brain stem were extremely small; and the tertiary sulci were absent in the cerebral surface. The cross-sectional area of cerebral cortex was reduced to about one third of those in the control, although six-layered lamination, density of pyramidal neurons, and expressions of calcium-binding proteins were comparatively preserved in the cerebral cortex. The third ventricle was hypoplastic, and the bilateral thalami appeared to be fused and the hippocampus was unrolled, whereas the corpus callosum was preserved. In the hypothalamus, the paraventricular nucleus was only identified, and the adenohypophysial somatotrophs were reduced. This may be the first autopsy report of Micro syndrome, which is characterized by microcephaly, brain malformations, optic atrophy, and hypogenitalism, although the case lacked agenesis of the corpus callosum.