Deficiency of complex II (succinate dehydrogenase, SDH) represents a rare cause of mitochondrial disease and is associated with a wide range of clinical symptoms. Recently, mutations of SDHAF1, the gene encoding for the SDH assembly factor 1, were reported in SDH-defective infantile leukoencephalopathy. Our goal was to identify SDHAF1 mutations in further patients and to delineate the clinical phenotype.

Heterozygous mutations in the ATP1A3 gene, coding for an alpha subunit isoform (α3) of Na+/K+-ATPase, are the primary genetic cause for rapid-onset dystonia-parkinsonism (RDP) and alternating hemiplegia of childhood (AHC). Recently, cerebellar ataxia, areflexia, pes cavus, optic atrophy and sensorineural hearing loss (CAPOS), early infantile epileptic encephalopathy (EIEE), childhood rapid onset ataxia (CROA) and relapsing encephalopathy with rapid onset ataxia (RECA) extend the clinical spectrum of ATP1A3 related disorders. AHC and RDP demonstrate distinct clinical features, with AHC symptoms being generally more severe compared to RDP. Currently, it is largely unknown what determines the disease severity, and whether severity is linked to the degree of functional impairment of the α3 subunit. Here we compared the effect of twelve different RDP and AHC specific mutations on the expression and function of the α3 Na+/K+-ATPase in transfected HEK cells and oocytes. All studied mutations led to functional impairment of the pump, as reflected by lower survival rate and reduced pump current. No difference in the extent of impairment, nor in the expression level, was found between the two phenotypes, suggesting that these measures of pump dysfunction do not exclusively determine the disease severity.

Mutations in PEX1 are the most common primary cause of Zellweger syndrome. In addition to exonic mutations, deletions and splice site mutations two 5' polymorphisms at c.-137 and c.-53 with a potential influence on PEX1 protein levels have been described in the 5' untranslated region (UTR) of the PEX1 gene.

Background: Alexander disease (AxD) is a rare severe leukodystrophy that has no cure to date. A pathogenic gain-of-function variant in the GFAP gene affects the astrocytes and subsequently the function of the white matter in the CNS. Methods: We retrospectively analyzed the most frequent symptoms of nine AxD cases, classified them according to published classifications, and described the need of care and support. Results: The description of the courses of disease of nine cases with AxD reflects the broad spectrum of different phenotypes of AxD, with often occurring apnoea. Data about care and support for AxD patients indicate a high and heterogeneous need of support. Treatment with steroids reduced symptoms in two patients. Some patients showed lasting improvement during their course of disease. Conclusions: The course of AxD is very heterogeneous. Thus, we extracted relevant key features to describe the severity of the disease, namely feeding problems, epilepsy, age-appropriate motor function, failure to thrive, age-appropriate language and apnoea. We recommend early evaluation for clinical care and support. For some AxD patients, treatment with steroids may alleviate symptoms. Further development of efficient treatments is necessary.