Abstract
Usually overlooked by physicians, olfactory abnormalities are not uncommon. Olfactory malformations have recently been reported in an emerging group of genetic disorders called Mendelian Disorders of the Epigenetic Machinery (MDEM). This study aims to determine the prevalence of olfactory malformations in a heterogeneous group of subjects with MDEM. We reviewed the clinical data of 35 patients, 20 females and 15 males, with a mean age of 9.52 years (SD 4.99). All patients had a MDEM and an already available high-resolution brain MRI scan. Two experienced neuroradiologists reviewed the MR images, noting abnormalities and classifying olfactory malformations. Main findings included Corpus Callosum, Cerebellar vermis, and olfactory defects. The latter were found in 11/35 cases (31.4%), of which 7/11 had Rubinstein-Taybi syndrome (RSTS), 2/11 had CHARGE syndrome, 1/11 had Kleefstra syndrome (KLFS), and 1/11 had Weaver syndrome (WVS). The irregularities mainly concerned the olfactory bulbs and were bilateral in 9/11 patients. With over 30% of our sample having an olfactory malformation, this study reveals a possible new diagnostic marker for MDEM and links the epigenetic machinery to the development of the olfactory bulbs.
Highlights
As we breathe, millions of airborne odorants get captured by appropriate receptors embedded in the cellular plasma membrane of sensory neurons located deep inside the nasal cavity initiating a complex biochemical response that leads to the perception of odors
Brain magnetic resonance imaging (MRI) scanning has commonly revealed brain malformations, which vary in type and severity
Our study focused on evaluating the presence of olfactory abnormalities in available brain MRIs of patients with Mendelian Disorders of the Epigenetic Machinery (MDEM)
Summary
Millions of airborne odorants get captured by appropriate receptors embedded in the cellular plasma membrane of sensory neurons located deep inside the nasal cavity initiating a complex biochemical response that leads to the perception of odors. Usually overlooked by physicians, olfactory abnormalities are not uncommon, with many conditions, mainly non-genetic, causing some disruption to the system. To the best of our knowledge, among these conditions are only a few complex genetic syndromes such as Kallman. Olfactory Malformations and Rare Diseases syndrome 1 (KS1, #308700), and CHARGE syndrome (#214800). The latter has recently been classified among an emerging group of extremely rare genetic disorders, the Mendelian Disorders of the Epigenetic Machinery (MDEM) (Fahrner and Bjornsson, 2019). Despite being a relatively young group, more than 80 conditions have already been identified. Common features are intellectual disability, abnormal growth, and brain and limb malformations. Disease severity and clinical presentation, vary widely
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