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Ann Clin Transl Neurol. 2018 Dec 3;6(1):114-120. doi: 10.1002/acn3.696. eCollection 2019 Jan.

Age-related phenotype and biomarker changes in SSADH deficiency.

Author information

1
Department of Neurology Boston Children's Hospital Harvard Medical School Boston Massachusetts.
2
Department of Pharmacotherapy College of Pharmacy and Pharmaceutical Sciences Washington State University Spokane Washington.

Abstract

Objective:

Succinic Semialdehyde Dehydrogenase (SSADH) deficiency is a disorder of elevated gamma-amino butyric acid (GABA) and gamma hydroxybutyric acid (GHB) and a complex neuropsychiatric profile. Adult reports suggest worsening epilepsy and high SUDEP risk.

Methods:

Subjects with confirmed SSADH deficiency were recruited into a longitudinal study. Plasma thyroid hormone and total GABA/GHB were quantified by standard clinical chemistry methodologies and mass spectrometry, respectively.

Results:

A total of 133 subjects with SSADH deficiency are enrolled in the registry; 49 participated in the longitudinal study. The age range of the population is 8 weeks to 63 years (median 7.75 year; 44% male). There is a significant difference in proportions among the age groups in subjects affected with hypotonia, compulsive behavior, sleep disturbances, and seizures. Epilepsy is present in 50% of the total population, and more prevalent in subjects 12 years and older (P = 0.001). The median age of onset for absence seizures was 2 years, and 12 years for generalized tonic-clonic seizures (P < 0.01). The SUDEP rate in adults was 12% (4/33). There was a significant age-dependent negative correlation between GABA and T3 levels.

Interpretation:

There is an age-dependent association with worsening of epilepsy, behavioral disturbances including obsessive-compulsive behavior, and sleep disturbances with age in SSADH deficiency. There is a high risk of SUDEP. We have observed more absence seizures in younger patients, compared to tonic-clonic in the older cohort, which correlates with age-related changes in GABA and GHB concentration and thyroid function, as well as the natural history of seizures in the murine model.

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