Syndromic microphthalmia | |
---|---|
Symptoms | Abnormally small eyeball(s) |
Usual onset | Birth [1] |
Duration | Lifelong [1] |
Causes | Genetic or environmental factors [1] |
Frequency | 1 in 10,000 individuals [1] |
Syndromic microphthalmia is a class of rare congenital anomalies characterized by microphthalmia along with other non-ocular malformations. [2] Syndromic microphthalmia accounts for 60 to 80% of all cases of microphthalmia. [2] Syndromic microphthalmias are caused by mutations in genes related to embryonic craniofacial development, and they are typically classified based on their genetic cause.
If microphthalmia is present, genetic testing can be done to inform a specific diagnosis of a named syndrome. Twenty to forty percent of anophthalmia and microphthalmia patients are diagnosed with a recognized syndrome. [2] There are 14 numbered syndromic microphthalmies (MCOPS) primarily defined by their ocular manifestations:
Type | Causative gene/locus | Inheritance [a] | Synonyms |
---|---|---|---|
MCOPS1 | NAA10 [3] | XL | Lenz microphthalmia syndrome |
MCOPS2 | BCOR [4] | XLR | |
XLD | oculofaciocardiodental syndrome | ||
MCOPS3 | SOX2 [2] | AD | SOX2 anophthalmia syndrome, anophthalmia/microphthalmia-esophageal atresia (AEG) syndrome |
MCOPS4 | Xq27-q28 [2] | XLR | microphthalmia-ankyloblepharon-intellectual disability syndrome |
MCOPS5 | OTX2 [2] | AD | OTX2-related eye disorders |
MCOPS6 | BMP4 [5] | AD | Bakrania-Ragge syndrome, microphthalmia with brain and digit anomalies |
MCOPS7 | HCCS, COX7B, NDUFB11 [2] [6] | XLD | MIDAS syndrome, microphthalmia with linear skin defects (MLS) syndrome |
MCOPS8 | SNX3 [7] | AD | microcephaly-microphthalmia ectrodactyly of lower limbs and prognathism (MMEP) syndrome, Viljoen–Smart syndrome |
MCOPS9 | STRA6 [8] | AR | anophthalmia/microphthalmia and pulmonary hypoplasia, Spear syndrome, Matthew–Wood syndrome |
MCOPS10 | unknown [2] | microphthalmia and brain atrophy (MOBA) syndrome | |
MCOPS11 | VAX1 [2] | AR | N/A |
MCOPS12 | RARB [2] | AD, AR | microphthalmia with or without pulmonary hypoplasia, diaphragmatic hernia, and/or cardiac defects |
MCOPS13 | HMGB3 [2] | XL | colobomatous microphthalmia with microcephaly, short stature, and psychomotor retardation, Maine microphthalmos |
MCOPS14 | MAB21L2 [2] | AD, AR | colobomatous microphthalmia-rhizomelic dysplasia syndrome, microphthalmia-coloboma-rhizomelic skeletal dysplasia |
In addition to MCOPS1–14, there are many genetic syndromes of which microphthalmia is a key feature: [2]
Causative gene/locus | Inheritance [a] | Name/synonyms |
---|---|---|
unknown | XLD | Aicardi syndrome (AIC), agenesis of corpus callosum with chorioretinal abnormality |
KIAA1109 | AR | Alkuraya–Kucinskas syndrome (ALKKCUS) |
MAF | AD | Aymé–Gripp syndrome (AYGRP) |
ACTB | AD | Fryns-Aftimos syndrome, Baraitser–Winter syndrome 1 (BRWS1) |
ACTG1 | AD | Baraitser–Winter syndrome 2 (BRWS2) |
unknown | Biemond syndrome | |
FOXL2 | AD | Blepharophimosis, ptosis, epicanthus inversus syndrome (BPES) |
SMCHD1 | AD | Bosma arhinia microphthalmia syndrome (BAMS) |
TFAP2A | AD | Branchio-oculo-facial syndrome (BOFS), hemangiomatous branchial clefts-lip pseudocleft syndrome |
ERCC6 | AR | Cockayne syndrome type B (CSB), cerebro-oculo-facio-skeletal syndrome 1 (COFS1) |
CHD7 | AD | CHARGE syndrome |
HDAC6 | XLD | Chondrodysplasia with platyspondyly, distinctive brachydactyly, hydrocephaly, and microphthalmia |
unknown | Colobomatous microphthalmia-obesity-hypogenitalism-intellectual disability syndrome | |
YAP1 | AD | Coloboma, ocular, with or without hearing impairment, cleft lip/palate, and/or intellectual disability (COB1) |
FAT1 | AR | Colobomatous microphthalmia, ptosis, nephropathy, and syndactyly |
MITF | AD | Waardenburg syndrome type 2 |
AR | COMMAD syndrome | |
SRD5A3 | AR | Congenital disorder of glycosylation type 1q (CDG1q) |
SMO | unknown | Curry–Jones syndrome (CJS) |
SALL4 | AR | Duane-radial ray syndrome, Okihiro syndrome |
FANCA, FANCD2, FANCE, FANCI, FANCL | AR | Fanconi anemia complementation groups A, D2, E, I, L |
PORCN | XLD | Focal dermal hypoplasia, Goltz-Gorlin syndrome |
FRAS1 | AR | Fraser syndrome 1 |
FREM2 | AR | Fraser syndrome 2 |
GRIP1 | AR | Fraser syndrome 3 |
ALX3 | AR | Frontonasal dysplasia 1 (FND1) |
ALX1 | AR | Frontonasal dysplasia 3 (FND3) |
unknown | AR | Fryns syndrome |
unknown | GOMBO syndrome (growth retardation, ocular abnormalities, microcephaly, brachydactyly, and oligophrenia) | |
SLC25A24 | AD | Gorlin–Chaudhry–Moss syndrome |
FAM111A | AD | Gracile bone dysplasia (GCLEB), Kenny-Caffey syndrome |
unknown | Hallermann–Streiff syndrome | |
SMG9 | AR | Heart and brain malformation syndrome (HBMS) |
14q32 | AD | Hemifacial microsomia |
SIX3 , SHH , PTCH1 , GLI2 | AD | Holoprosencephaly types 1, 2, 3, 7, 9 |
IKBKG | XLD | Incontinentia pigmenti |
PDE6D | AR | Joubert syndrome 22 |
unknown | AR | Kapur–Toriello syndrome |
KMT2D | AD | Kabuki syndrome |
KDM6A | XLD | |
GDF6 | AD | Klippel–Feil syndrome types 1, 3 |
GDF3 | XLD | |
unknown | XLD | Macrosomia with lethal microphthalmia |
FREM1 | AR | Manitoba oculotrichoanal syndrome (MOTA) |
MKS1 , TMEM216 , TMEM67 , CEP290 , RPGRIP1L | AR | Meckel–Gruber syndrome types 1-5 |
unknown | likely AD | MOMO syndrome |
ZEB2 | AR | Mowat–Wilson syndrome |
POMT1 | AD | Muscle–eye–brain disease type A 1-11 |
POMT2 , POMGNT1 , FKTN , FKRP , CRPPA , POMGNT2 , DAG1 , RXYLT1 , B3GALNT2 | AR | |
NHS | XLD | Nance–Horan syndrome |
RERE | AD | Neurodevelopment disorder with anomalies of the brain, eye, and/or heart (NEDBEH) |
NPD | XLR | Norrie disease |
HMX1 | AR | Oculoauricular syndrome |
GJA1 | AD, AR | Oculodentodigital dysplasia (ODD) |
CPLANE1 | AR | Orofaciodigital syndrome type VI |
LRP5 | AR | Osteoporosis-pseudoglioma syndrome |
PAX2 | AD | Papillorenal syndrome |
ATOH7 | AR | Persistent fetal vasculature (PFV)/persistent hyperplastic primary vitreous (PHPV) |
RIPK4 | AR | Popliteal pterygium syndrome (PPS) |
PQBP1 | XLR | Renpenning's syndrome |
RBP4 | AR | Retinal dystrophy, iris coloboma and comedogenic acne syndrome (RDCCAS) |
DLX1 , DLX2 | AD | Split-hand/foot malformation type V |
C12orf57 | AR | Temtamy syndrome |
WNT3 | AR | Tetra-amelia syndrome |
SALL1 | AD | Townes–Brocks syndrome |
PUF60 | AD | Verheij syndrome |
RAB3GAP1, RAB3GAP2, RAB18, TBC1D20 | AR | Warburg Micro syndrome 1-4 |
A coloboma is a hole in one of the structures of the eye, such as the iris, retina, choroid, or optic disc. The hole is present from birth and can be caused when a gap called the choroid fissure, which is present during early stages of prenatal development, fails to close up completely before a child is born. Ocular coloboma is relatively uncommon, affecting less than one in every 10,000 births.
Microphthalmia, also referred as microphthalmos, is a developmental disorder of the eye in which one or both eyes are abnormally small and have anatomic malformations. Microphthalmia is a distinct condition from anophthalmia and nanophthalmia. Although sometimes referred to as 'simple microphthalmia', nanophthalmia is a condition in which the size of the eye is small but no anatomical alterations are present.
Intraflagellar transport (IFT) is a bidirectional motility along axoneme microtubules that is essential for the formation (ciliogenesis) and maintenance of most eukaryotic cilia and flagella. It is thought to be required to build all cilia that assemble within a membrane projection from the cell surface. Plasmodium falciparum cilia and the sperm flagella of Drosophila are examples of cilia that assemble in the cytoplasm and do not require IFT. The process of IFT involves movement of large protein complexes called IFT particles or trains from the cell body to the ciliary tip and followed by their return to the cell body. The outward or anterograde movement is powered by kinesin-2 while the inward or retrograde movement is powered by cytoplasmic dynein 2/1b. The IFT particles are composed of about 20 proteins organized in two subcomplexes called complex A and B.
Anophthalmia is the medical term for the absence of one or both eyes. Both the globe and the ocular tissue are missing from the orbit. The absence of the eye will cause a small bony orbit, a constricted mucosal socket, short eyelids, reduced palpebral fissure and malar prominence. Genetic mutations, chromosomal abnormalities, and prenatal environment can all cause anophthalmia. Anophthalmia is an extremely rare disease and is mostly rooted in genetic abnormalities. It can also be associated with other syndromes.
Laminopathies are a group of rare genetic disorders caused by mutations in genes encoding proteins of the nuclear lamina. Since the first reports of laminopathies in the late 1990s, increased research efforts have started to uncover the vital role of nuclear envelope proteins in cell and tissue integrity in animals. Laminopathies are a group of degenerative diseases, other disorders associated with inner nuclear membrane proteins are known as nuclear envelopathies.
Vitamin A receptor, Stimulated by retinoic acid 6 or STRA6 protein was originally discovered as a transmembrane cell-surface receptor for retinol-binding protein. STRA6 is unique as it functions both as a membrane transporter and a cell surface receptor, particularly as a cytokine receptor. In fact, STRA6 may be the first of a whole new class of proteins that might be known as "cytokine signaling transporters." STRA6 is primarily known as the receptor for retinol binding protein and for its relevance in the transport of retinol to specific sites such as the eye. It does this through the removal of retinol (ROH) from the holo-Retinol Binding Protein (RBP) and transports it into the cell to be metabolized into retinoids and/or kept as a retinylester. As a receptor, after holo-RBP is bound, STRA6 activates the JAK/STAT pathway, resulting in the activation of transcription factor, STAT5. These two functions—retinol transporter and cytokine receptor—while using different pathways, are processes that depend on each other.
Usherin is a protein that in humans is encoded by the USH2A gene.
Gap junction beta-3 protein (GJB3), also known as connexin 31 (Cx31) — is a protein that in humans is encoded by the GJB3 gene.
Alpha-tectorin is a protein that in humans is encoded by the TECTA gene.
Sodium bicarbonate transporter-like protein 11 is a protein that in humans is encoded by the SLC4A11 gene.
Cytochrome c-type heme lyase is an enzyme that in humans is encoded by the HCCS gene on chromosome X.
Gerodermia osteodysplastica (GO) is a rare autosomal recessive connective tissue disorder included in the spectrum of cutis laxa syndromes.
Hennekam syndrome, also known as intestinal lymphagiectasia–lymphedema–mental retardation syndrome, is an autosomal recessive disorder consisting of intestinal lymphangiectasia, facial anomalies, peripheral lymphedema, and mild to moderate levels of growth and intellectual disability.
Perlman syndrome (PS), also known as nephroblastomatosis-fetal ascites-macrosomia-Wilms tumor syndrome, is a rare overgrowth syndrome caused by autosomal recessive mutations in the DIS3L2 gene. PS is characterized by macrocephaly, neonatal macrosomia, nephromegaly, renal dysplasia, dysmorphic facial features, and increased risk for Wilms' tumor. The syndrome is associated with high neonatal mortality.
Forkhead box protein E3 (FOXE3) also known as forkhead-related transcription factor 8 (FREAC-8) is a protein that in humans is encoded by the FOXE3 gene located on the short arm of chromosome 1.
De Barsy syndrome is a rare autosomal recessive genetic disorder. Symptoms include cutis laxa as well as other eye, musculoskeletal, and neurological abnormalities. It is usually progressive, manifesting side effects that can include clouded corneas, cataracts, short stature, dystonia, or progeria.
Retinal homeobox protein Rx also known as retina and anterior neural fold homeobox is a protein that in humans is encoded by the RAX gene. The RAX gene is located on chromosome 18 in humans, mice, and rats.
Impute.me was an open-source non-profit web application that allowed members of the public to use their data from direct-to-consumer (DTC) genetic tests to calculate polygenic risk scores (PRS) for complex diseases and cognitive and personality traits. In July 2022, Lasse Folkerson, initiator and operator of impute.me, took the website offline.
Waardenburg anophthalmia syndrome is a rare autosomal recessive genetic disorder which is characterized by either microphthalmia or anophthalmia, osseous synostosis, ectrodactylism, polydactylism, and syndactylism. So far, 29 cases from families in Brazil, Italy, Turkey, and Lebanon have been reported worldwide. This condition is caused by homozygous mutations in the SMOC1 gene, in chromosome 14.
Curry–Jones syndrome is a rare genetic disorder characterized by congenital brain, osseous, cutaneous, ocular, and intestinal anomalies.
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