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Catarina Borges1; Tânia Mendo1, Sílvia Sequeira2, Sandra Jacinto3, Fátima Furtado1

1 - Departamento de Pediatria, Unidade Local de Saúde do Baixo Alentejo, Beja, Portugal
2 - Unidade de Doenças Metabólicas, Departamento de Pediatria, Hospital Dona Estefânia, Centro Hospitalar de Lisboa Central, Lisboa
3 - Departamento de Neurologia Pediátrica, Hospital Dona Estefânia, Centro Hospitalar de Lisboa Central, Lisboa

8th Excellence in Pediatrics, Londres 8-10 Dezembro 2016 (poster)

Introduction: Christianson syndrome is a rare genetic condition, inherited in an X-linked recessive pattern, with an unknown prevalence, associated with mutations in the SLC9A6 gene. It affects mainly the nervous system, causing intellectual disability with absent speech, epilepsy and ataxia.
Clinical Case: We describe the case of an 8-year-old Caucasian male child, without inbreeding, followed by our paediatric neurology team since he was two and a half years old. He had an apparently non-progressive condition characterized by severe cognitive deficit with no language, pervasive developmental disorder, epilepsy and dysmorphic facies. Other findings included convergent strabismus, autonomous gait with some imbalance and pyramidal signs in the lower limbs. Investigations revealed a normal brain MRI (2009) and negative genetic studies (karyotyping, fragile X syndrome, Smith-Lemli-Opitz syndrome, non-specific intellectual disability sequencing panel, including Angelman syndrome, and array CGH). In March 2015, following a viral upper respiratory tract infection, he presented with progressive prostration and decreased spontaneous movements, with axial and appendicular ataxia, with no other abnormal movements. Further investigations showed: a brain MRI revealing important cerebellar atrophy with hyperintensity of the cerebellar cortex, an EEG with abundant paroxysmal activity in the left frontal region, with increased sleepiness, a normal skin biopsy, and several metabolic studies that were inconclusive (amino acids, organic acids, redox potential, biotinidase, carbohydrate deficient transferrin, creatine metabolism, mucopolysaccharides and oligosaccharides). He clinically showed slight improvement after the acute episode, but without recovery of prior neurological status, maintaining inability to walk on his own. Since his clinical presentation at the moment fulfilled some of the criteria for Christianson syndrome (delayed development, intellectual disability, absence of language, ataxia, epilepsy, loss of ability to walk and dysmorphic features), genetic testing was performed and showed a mutation variant previously not described in the literature.
Conclusion: Rare disorders, also referred as orphan diseases, are diseases that affect a small percentage of the population therefore leading to a lack of experience of specialists. This fact implies that a great amount of suspicion, several years of investigations and multiple consultations are sometimes necessary in order to reach an accurate diagnosis. The correct diagnosis however is important in order to offer a more accurate prognosis and proper genetic counselling in future pregnancies.

Palavras Chave: Christianson syndrome, SLC9A6 gene, intellectual disability, cerebellar atrophy