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Dysmorpholoy
Hearing Loss
| Question | Answer |
|---|---|
| What percent of congenital deafness is genetic? | 60% |
| Of the genetic causes of congenital deafness, what percent is AR? | 75% |
| What % of genetic deafness is non-syndromic? (AR, AD) | 70% AR, 30% AD |
| Teratogen known to induce congenital hearing loss | hydantoin |
| Prematurity and congenital deafness | hyperbilrubinemia, low birthweight, NICU, ventilation, NICU, neonatal distress (?) |
| Other increased susceptabilities to congenital hearing loss | ototoxic medds, meningitis |
| Congenital CMV | neurosensory hearing loss, microcephaly, intracranial calcifications, mental retardation, CP, optic atrophy, reintopathy, cataracts, microhthalmia |
| Hearing loss and CMV... occurs in | <5% of pregnancies |
| CMV crosses the placenta | 30-40% of the time, with hearing loss occurring in 25% of these cases |
| The most common cause of congenital hearing loss, accounting for about 4000 LBs annually, may be... | CMV |
| Epidemiology of NSHL | AR- 80%, AD-15%, XL-5%, mt-2% (Empiric risk for single case 10%) |
| AR-NSHL | usually congenital, severe to profound, 50% are of connecin 26 |
| Connexin 26 (DFNb1/GJB2) | 13q12, 2 common mutations that account for 10% of all pre-lingual deafness, 1 allele causes dominant deafness (DFNA3) |
| Connexin 26 | Inner ear in the non-sensory epithelium of the Organ of Corti, potassium recycling pathway |
| Connexin 26 phenotype | 1. Non-syndromic, normal vision and vestibular function, non-progressive, hearing loss is mild to profound with intra- and inter-familial variability and few kindreds are progressive and asymmetric |
| DFNB2/ MYO7A | 11q13.5, expression only in hair cells of Organ of Corti, some mutations cause Usher Syndrome |
| AD-NSHL | Usually post-lingual, progressive (onset in 2nd or 3rd decades) |
| XL-NSHL | DFN3: progressive and mixed deafness with fixed stapes and perilympathetic gusher, a communication between meatus and cochlea, leads to gusher is the spates is disturbed. |
| Syndromic Hearing Loss | 1. Aport 2. BOR 3. Jervell and Lnage-nielson, 4. NF type 2, 5. Pendred 6. Waardenburg |
| Alport syndrome | Type 4, major collagen, neurosensory hearing loss |
| Branchio-Oto-Renal Syndrome | 8q13.3, AD, inner ear malformations, renal anomalies including agenesis present |
| Jervell and Lange-Nielsen syndrome | AR, profound congenital hearing loss, sudden death due to prolonged QT, high prevalence in Norway |
| Jervell and Lange-Nielsen syndrome genes | KCNQ1 and KCNE2 (potassium channel genes AD or AR |
| Pendred syndrome | neurosensory hearing loss with iodide tripping defect of the htyroid gland, thyroid disease may be clinically non-apparent, GOLD STANDARD: perchllorate washout, vestibular anomalies (23rd) |
| Pendred syndrome genes | 7q21-24, 16 diffeernt mutations described in two common genes, transporter/chloride/iodide issues |
| Waardenburg syndrome | Neurosensory hearing loss, lateral displacement of inner cnathi, lacrimal punctae |
| Isolated mitochondrial hearing loss | Sometimes co-segregates with skin conditions, penetrance of hearing loss is extremely ehtnic dependent (modifier genes necessary) |
| Mitochondrial syndromes and hearing loss | Diabetes-hearing loss after onset of diabetes, MELAS, Presbycusis |
| Hearing loss with visual problems (syndromes) | 1. Usher syndrome, Wolfram, Norrie, MtDOs |
| Usher syndrome | 1. Association of hearing loss with reinitis pigmentosa, at least 11 loci and 2 identified |
| Primary inner-ear malformations | Michel and Mondini, and also enlarged vestibular aqueduct |
| Michel | complete aplasia of inner ear structure |
| Mondini | 1 1/2 tums of cochlea, dysplasia of apex |
| Medical genetics of hearing loss stage 1 | medical genetics, audiology, otolaryngology |
| Medical genetics of hearing loss stage 2 | vestibular, ophthalmology, CT of temporal bones, urinalysis/serum creatinine, serology |
| Medical genetics of hearing loss stage 3 | perchlorate discharge (if CT abnormal), DNA, electrocardiogram, electroreinogram |
| Examples of gene testing for hearing loss | 1. Connexin 26, Pendred syndrome, Stickler syndrome |
Created by:
KChatham
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