The m.3243A > G mutation has become known as the MELAS mutation. However, many other clinical phenotypes associated with this mutation have been described, most frequently being maternally inherited diabetes and deafness (MIDD). The m.3243A > G mutation, can be detected in virtually all tissues, however heteroplasmy differs between samples. Recent reports indicate, a preference to perform mutation analysis in urinary epithelial cells (UEC). To test this, and to study a correlation between the mutational load in different tissues with two mitochondrial scoring systems (NMDAS and NPMDS) we investigated 34 families carrying the m.3243A > G mutation. Heteroplasmy was determined in three non-invasively collected samples, namely leucocytes, UEC and buccal mucosa. We included 127 patients, of which 82 carried the m.3243A > G mutation. None of the children (n = 11) had specific complaints. In adults (n = 71), a median NMDAS score of 15 (IQR 10-24) was found. The most prevalent symptoms were hearing loss(48%), gastro-intestinal problems(42%), exercise intolerance(38%) and glucose intolerance(37%). Ten patients had neurologic involvement. Buccal mucosa had the best correlation with the NMDAS in all adults (r = 0.437,p < 0.001), whereas UEC had the strongest correlation with the NMDAS in severely affected patients (r = 0.593,p = 0.002). Heteroplasmy declined significantly with increasing age in all three samples (leucocytes r = -0.705 (p < 0.001), UEC r = -0.374(p = 0.001), buccal mucosa r = -0.460(p < 0.001). In our cohort of 82 patients, the m.3243A > G mutation causes a wide variety of signs and symptoms, MIDD being far more prevalent than MELAS. Looking at the characteristics of the three non-invasively available tissues for testing heteroplasmy we confirm that UEC are the preferred sample to test.

Although PRES has predominantly been described in leukemia patients, it occurs in children with solid tumors as well. Hypertension seems to be the most important trigger for the occurrence of PRES during childhood cancer treatment. Seizures are the most common accompanying sign. Symptoms and radiological findings normalize in ∼90% of the cases, but in 10% neurological symptoms remain.

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Measuring FGF21 concentration had little added value in monitoring and predicting the disease course in this specific patient group.

In this observational cohort study, we examined the prognostic value of growth and differentiation factor 15 (GDF15) in indicating and monitoring general mitochondrial disease severity and progression in adult carriers of the m.3243A>G mutation.Ninety-seven adult carriers of the m.3243A>G mutation were included in this study. The Newcastle mitochondrial disease adult scale was used for rating mitochondrial disease severity. In parallel, blood was drawn for GDF15 analysis by ELISA. Forty-nine carriers were included in a follow-up study. In a small subset of subjects of whom an echocardiogram was available from general patient care, myocardial deformation was assessed using two-dimensional speckle-tracking strain analysis.A moderate positive correlation was found between the concentration of GDF15 and disease severity (r ¼ 0.59; p < 0.001). The concentration of serum GDF15 was higher in m.3243A>G carriers with diabetes mellitus, cardiomyopathy, and renal abnormalities. After a 2-year follow-up, no significant correlation was found between the change in disease severity and the change in the concentration of GDF15 or between the GDF15 level at the first assessment and the change in disease severity. In the subcohort of patients of whom an echocardiogram was available, the concentration of GDF15 correlated moderately to longitudinal global strain (r ¼ 0.55; p ¼ 0.006; n ¼ 23) but not to circumferential or radial strain.Our results indicate that serum GDF15 is not a strong surrogate marker for general mitochondrial disease severity. Its value in indicating myocardial deformation should be confirmed in a prospective longitudinal study.