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P428 An interesting case of a girl with a de novo unbalanced translocation causing distinctive metabolic markers

Background A five year-old girl was referred to the National Centre for Inherited Metabolic Disorders with a background of a neonatal seizure on day three of life in the context of hypoglycaemia and weight loss. She had learning difficulties and gross motor and speech delay. To investigate her developmental delay an MRI brain was carried out at 3 years of age which demonstrated extensive signal abnormality in the deep white matter with numerous tiny areas of high T2 and FLAIR signal abnormality which was felt reflected either neonatal hypoxic ischaemic encephalopathy or neonatal hypoglycaemia or both. A metabolic cause was considered at that time and an initial screen was normal; the patient had also undergone a microarray. Investigations Metabolic investigations were conducted in parallel with detailed genetic studies to search for an encompassing diagnosis. The girl was diagnosed with a de novo unbalanced translocation between the long arm of chromosome×and duplication of the long arm of chromosome 13, der(X)t(X;13)(q25;q12.11)dn. A blood sample revealed slightly abnormal glycosylation of transferrin isoforms with increased loss of one sialic acid (8.3%, reference range <6%). This was repeated with a result of 8.6%. However it was felt that this was not consistent with a primary diagnosis of congenital disorder of glycosylation (CDG) type 1 and not definitive of a CDG type 2. Results On review of all of the results it was felt that the genetic abnormality identified was responsible for this girl’s clinical presentation. Her MRI seemed more likely to reflect a developmental brain disorder or reflective of the neonatal events. There are genes for CDG on both the×chromosome and chromosome 13 but neither appear to be at the position of her breakpoint; this could explain her distinctive glycosylation abnormalities as a secondary phenomenon. Conclusions Our patient is clinically making pleasing developmental progress though recently had a recurrence of seizures after a prolonged seizure free period. This case demonstrates how important it is to consider all the biochemical and genetic information available in a clinical context to differentiate between primary and secondary findings. This will guide towards accurate diagnostic labelling, streamline follow-up and enable appropriately directed care.