Abstract
SATB2-associated syndrome (SAS) is an autosomal dominant neurogenetic multisystemic disorder. We describe two individuals with global developmental delay and hypotonia who underwent an extensive evaluation to rule out an underlying mitochondrial disorder before their eventual diagnosis of SAS. Although the strict application of the clinical mitochondrial disease score only led to the designation of “possible” mitochondrial disorder for these two individuals, other documented abnormalities included nonspecific neuroimaging findings on magnetic resonance imaging and magnetic resonance spectroscopy, decreased complex I activity on muscle biopsy for patient 2, and variation in the size and relative proportion of types of muscle fibers in the muscle biopsies that were aligned with mitochondrial diseases. SAS should be in the differential diagnoses of mitochondrial disorders, and broad-spectrum diagnostic tests such as exome sequencing need to be considered early in the evaluation process of undiagnosed neurodevelopmental disorders.
Highlights
Mitochondrial diseases are a heterogeneous group of clinical disorders due to deficiency of the respiratory chain
Whether primary mitochondrial disease (PMD) or secondary mitochondrial dysfunction (SMD), mitochondrial disorders are typically characterized by a broad clinical spectrum often involving multiple organs such as skeletal muscles, brain, heart, liver, kidney, or endocrine glands (Bianchi et al, 2003)
Mitochondrial diseases with respiratory chain dysfunction are characterized by a broad phenotype
Summary
Mitochondrial diseases are a heterogeneous group of clinical disorders due to deficiency of the respiratory chain. While primary mitochondrial disease (PMD) refers to disorders whose underlying genetic cause directly impairs the composition or function of the electron respiratory chain, secondary mitochondrial dysfunction (SMD), by contrast, refers to any abnormal mitochondrial function other than PMD (Falk, 2010). Whether PMD or SMD, mitochondrial disorders are typically characterized by a broad clinical spectrum often involving multiple organs such as skeletal muscles, brain, heart, liver, kidney, or endocrine glands (Bianchi et al, 2003). Given the described overlapping clinical phenotypes between mitochondrial diseases and SAS, early in life, we conclude that SAS should be considered in the differential diagnosis of individuals undergoing evaluation for mitochondrial dysfunction
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