We compared the frequency of phenotypic features of 40 children with Down syndrome between individuals with a maternally or paternally derived extra chromosome 21, using quantitative FISH for comparing heteromorphisms of the nucleolar organizing region. Parental origin was determined in 90% of families. Hypotonia and craniofacial abnormalities were present in 90% or more individuals, irrespective of parental origin of chromosome 21. Congenital heart defects were more frequent in cases with a maternally derived extra chromosome 21. Imprinted gene(s) may contribute to the development of congenital heart defects in Down syndrome.
Case ReportX-linked myotubular myopathy (XLMTM; MIM# 310400) is a severe congenital muscle disorder caused by mutations in the MTM1 gene. It is characterised by severe hypotonia and generalised muscle weakness in affected males, and is generally a fatal disorder in the neonatal period and early infancy.Male twins were delivered vaginally at 33 + 4 weeks gestation following onset of preterm labour at a private hospital. Twin 1 was born by vaginal delivery with cephalic presentation; there had been a non-reassuring CTG with a fetal bradycardia. His APGAR scores were 1-3-5 at 1, 5 and 10 min, respectively. He was intubated and resuscitated with two boluses of normal saline for signs and symptoms of shock secondary to extensive bilateral cephalhaematomas. Twin 2 was born vaginally as a footling breech presentation. His APGAR scores were 1-5-5 at 1, 5 and 10 min, respectively. He required resuscitation at birth with intubation and a normal saline bolus because of signs and symptoms of shock as a result of extensive bilateral cephalhaematomas. He also sustained a fractured left femur and right humerus. The preliminary diagnosis at the time of request for retrieval was hypoxic ischaemic encephalopathy.Twin 1 was administered surfactant prior to transfer to our neonatal intensive care unit. On admission, he was managed with a transfusion of packed red blood cells (PRBCs) for ongoing evidence of shock secondary to blood loss. The coagulation profile was normal. On examination, he displayed marked hypotonia, an absent gag reflex and decreased overall activity. Seizures were noted on amplitude electroencephalogram monitoring and were treated with phenobarbitone (one dose), after which no further seizures were observed. Cranial magnetic resonance imaging (MRI) was performed on day 5 of life and revealed large bilateral subdural hygromas, the cause of which was unclear but may have possibly been secondary to subdural haemorrhages. There was no evidence of hypoxic ischaemic changes.On admission to the neonatal intensive care unit, twin 2 was managed with PRBCs, fresh frozen plasma, platelets and inotropes for signs and symptoms of shock from extensive blood loss because of the bilateral cephalhaematomas, fractured left femur and right humerus. On examination, he also displayed marked hypotonia, absent gag reflex, decreased overall activity and absent deep tendon reflexes. The initial MRI brain of twin 2 also showed large bilateral cephalhematomas and large subdural hygromas/effusions. As with his sibling, the underlying brain appeared normal with no evidence of hypoxic ischaemic change.Both twins had decreased muscle mass, temporal scalloping, thin ribs, long fingers and bilateral undescended testes. On further questioning, a history of polyhydramnios with decreased fetal movements in utero was obtained. The physical examination and lack of hypoxic ischaemic change on MRI suggested a neuromuscular disorder. A full metabolic screen revealed no abnormality. Spinal muscular atrophy (SMA) gene mutations for spinal muscular atroph...
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