A novel syndrome of lethal familial hyperekplexia associated with brain malformation
- Equal contributors
1 Neonatology Unit, Department of Pediatrics, Security Forces Hospital, Riyadh, Saudi Arabia
2 Division of Pediatric Neurology, Department of Pediatrics (39), College of Medicine, King Saud University, P. O. Box 2925, Riyadh, 11461, Saudi Arabia
3 Division of Pediatric Neurology, Department of Pediatrics Security Forces Hospital, Riyadh, Saudi Arabia
4 Developmental Genetics Unit, Department of Genetics, King Faisal Specialist Hospital and Research left, Riyadh, Saudi Arabia
5 Department of Radiology and Diagnostic Imaging, King Khalid University Hospital and College of Medicine, King Saud University, Riyadh, Saudi Arabia
6 Division of Genetics, Department of Pediatrics, King Khalid University Hospital and College of Medicine, King Saud University, Riyadh, Saudi Arabia
7 Department of Anatomy and Cell Biology, College of Medicine, Al Faisal University, Riyadh, Saudi Arabia
BMC Neurology 2012, 12:125 doi:10.1186/1471-2377-12-125Published: 27 October 2012
Hyperekplexia (HPX) is a rare non-epileptic disorder manifesting immediately after birth with exaggerated persistent startle reaction to unexpected auditory, somatosensory and visual stimuli, and non-habituating generalized flexor spasm in response to tapping of the nasal bridge (glabellar tap) which forms its clinical hallmark. The course of the disease is usually benign with spontaneous amelioration with age. The disorder results from aberrant glycinergic neurotransmission, and several mutations were reported in the genes encoding glycine receptor (GlyR) α1 and β subunits, glycine transporter GlyT2 as well as two other proteins involved in glycinergic neurotransmission gephyrin and collybistin.
The phenotype of six newborns, belonging to Saudi Arabian kindred with close consanguineous marriages, who presented with hyperekplexia associated with severe brain malformation, is described. DNA samples were available from two patients, and homozygosity scan to determine overlap with known hyperkplexia genes was performed.
The kindred consisted of two brothers married to their cousin sisters, each with three affected children who presented antenatally with excessive fetal movements. Postnatally, they were found to have microcephaly, severe hyperekplexia and gross brain malformation characterized by severe simplified gyral pattern and cerebellar underdevelopment. The EEG was normal and they responded to clonazepam. All of the six patients died within six weeks. Laboratory investigations, including metabolic screen, were unremarkable. None of the known hyperkplexia genes were present within the overlapping regions of homozygosity between the two patients for whom DNA samples were available.
We present these cases as a novel syndrome of lethal familial autosomal recessive hyperekplexia associated with microcephaly and severe brain malformation.