The phenotypic spectrum of pathogenic ATP1A1 variants expands: the novel p.P600R substitution causes demyelinating Charcot-Marie-Tooth disease.

BACKGROUND: Charcot-Marie-Tooth disease (CMT) is a genetically and clinically heterogeneous group of inherited neuropathies. Monoallelic pathogenic variants in ATP1A1 were associated with axonal and intermediate CMT. ATP1A1 encodes for the catalytic α1 subunit of the Na+/ K+ ATPase. Besides neuropathy, other associated phenotypes are spastic paraplegia, intellectual disability, and renal hypomagnesemia. We hereby report the first demyelinating CMT case due to a novel ATP1A1 variant. METHODS: Whole-exome sequencing on the patient's genomic DNA and Sanger sequencing to validate and confirm the segregation of the identified p.P600R ATP1A1 variation were performed. To evaluate functional effects, blood-derived mRNA and protein levels of ATP1A1 and the auxiliary ß1 subunit encoded by ATP1B1 were investigated. The ouabain-survival assay was performed in transfected HEK cells to assess cell viability, and two-electrode voltage clamp studies were performed in Xenopus oocytes. RESULTS: The variant was absent in the local and global control datasets, falls within a highly conserved protein position, and is in a missense-constrained region. The expression levels of ATP1A1 and ATP1B1 were significantly reduced in the patient compared to healthy controls. Electrophysiology indicated that ATP1A1p.P600R injected Xenopus oocytes have reduced Na+/ K+ ATPase function. Moreover, HEK cells transfected with a construct encoding ATP1A1p.P600R harbouring variants that confers ouabain insensitivity displayed a significant decrease in cell viability after ouabain treatment compared to the wild type, further supporting the pathogenicity of this variant. CONCLUSION: Our results further confirm the causative role of ATP1A1 in peripheral neuropathy and broaden the mutational and phenotypic spectrum of ATP1A1-associated CMT.

Familial Mediterranean fever: risk factors, causes of death, and prognosis in the colchicine era.

We assessed the risk factors and causes of death in patients with familial Mediterranean fever (FMF) in an era when colchicine is the standard therapy for all patients.This study included all FMF patients who had presented to any of the internal medicine, rheumatology, or nephrology clinics at Dokuz Eylul University Hospital between 1992 and 2009. Of the 650 patients with FMF identified, 587 (90.3%) had either a face-to-face (n = 380) or telephone (n = 193) interview, or were confirmed as deceased. A structured questionnaire was used to obtain socioeconomic and demographic data, presenting and cumulative clinical features, and disease severity scores.During the follow-up period mortality was analyzed by calculating age- and sex-standardized mortality ratio (SMR) according to the mortality statistics of the Turkish population. Factors predictive of mortality were evaluated using Kaplan-Meier and Cox proportional hazard models. Sixty-three (9.7%) patients whose initial demographic and major clinical characteristics were similar to the rest of the group could not be contacted during the study period.Most (94.2%) patients were on colchicine at the time of the study. Thirty-seven (6.3%) patients had biopsy-verified amyloidosis, and 44 (7.5%) had renal disease. During a median follow-up of 6 years, 14 patients (9 women) died, and amyloidosis and its related complications were the leading causes of death in 7 patients. Univariate analysis revealed that increasing age, coronary heart disease, hypertension, renal disease, and amyloidosis were associated with mortality. However, Cox regression analysis showed amyloidosis as the only significant predictor of mortality (p < 0.001). The overall patient survival rate was not significantly different from the age- and sex-matched Turkish general population (SMR, 1.48; 95% confidence interval, 0.817-2.49).Our findings suggest that although the survival of FMF patients in the colchicine era is comparable to that of the general population, renal involvement still predicts mortality.

Down-regulation of adiponectin in patients with familial Mediterranean fever during attack-free period.

To evaluate the circulating levels of adipokines (leptin and adiponectin) and ghrelin in patients with familial Mediterranean fever (FMF) and also to assess the relationships between these molecules and disease-related parameters. Forty-eight FMF patients in attack-free period (31 men, [M], 17 women, [F], mean age 35.8 ± 8.6 years, and a mean body mass index [BMI] of 24.7 ± 3.1) and 40 age-, sex-, and BMI-matched healthy controls (24 M, 16 F, mean age 35.5 ± 8.5 years, and a mean BMI of 24.5 ± 2.8) were included in the study. Patients and controls with a history of any other chronic diseases and obese or underweight subjects were excluded. High-sensitive C-reactive protein (hs-CRP), leptin, adiponectin, and total ghrelin concentrations were studied. Age, sex, BMI, waist circumference, and smoking status were similar between FMF patients and controls (P > 0.05). Adipose tissue-derived molecules including leptin, and adiponectin were lower than healthy controls but only adiponectin levels reached the statistically significance (16.7 ± 8.9 ng/ml vs. 27.7 ± 15.9 ng/ml, P < 0.001) and leptin concentrations just missed significance (25.2 ± 16.2 ng/ml vs. 34.9 ± 27.2 ng/ml, P = 0.051). Ghrelin concentrations were not different between the groups. Adiponectin levels were significantly and negatively correlated with hs-CRP (P < 0.05, r = -0.24). The results of this study suggest that low-grade chronic inflammation during attack-free period in FMF patients may suppress adiponectin production or low levels of adiponectin might contribute to subclinical inflammation in these patients.