Clinical Guidance

Succinic semialdehyde dehydrogenase (SSADH) deficiency is characterized by a relatively non-progressive encephalopathy typically presenting with hypotonia and delayed acquisition of motor and language developmental milestones in the first two years of life. Common clinical features include an almost universal intellectual disability and adaptive function deficits, as well as epilepsy, autism spectrum disorder, movement disorders (such as ataxia, dystonia, and exertional dyskinesia), sleep disturbances, attention problems, anxiety, and obsessive-compulsive behaviors. Notably, seizures, autism spectrum disorder features, and behavioral problems tend to worsen around the time of late childhood or early adolescence . Affected individuals do not usually have episodic decompensation following metabolic stressors, as is typical of other organic acidemias and metabolic encephalopathies, although some have been diagnosed after having unanticipated difficulty recovering from otherwise ordinary childhood illnesses. Clinical presentation with acute onset of generalized hypotonia and choreiform movement following upper-respiratory tract infection has been reported . summarizes the common features seen in this condition. Table 2. Succinic Semialdehyde Dehydrogenase Deficiency: Frequency of Select Features

Diagnostic Criteria

Suggestive Findings

Succinic semialdehyde dehydrogenase (SSADH) deficiency should be suspected in individuals with the following clinical, imaging, and supportive laboratory findings and family history. Clinical findings. Late-infantile to early-childhood onset, slowly progressive or static encephalopathy characterized by:

• Developmental delay and/or cognitive deficiency, often with prominent expressive language deficit

Management Guidelines

Consensus clinical management guidelines for succinic semialdehyde dehydrogenase (SSADH) deficiency have been published .

Evaluations Following Initial Diagnosis

To establish the extent of disease and needs in an individual diagnosed with SSADH deficiency, the evaluations summarized (if not performed as part of the evaluation that led to diagnosis) are recommended.

Surveillance Guidelines

To monitor existing manifestations, the individual's response to supportive care, and the emergence of new manifestations, the evaluations summarized in are recommended.

Table 5.

Succinic Semialdehyde Dehydrogenase Deficiency: Recommended Surveillance

System/Concern | Evaluation | Frequency

Neurologic