Complement activation prior to symptom onset in myeloperoxidase ANCA-associated vasculitis but not proteinase 3 ANCA associated vasculitis - A Swedish biobank study.

OBJECTIVE: Increased soluble levels of complement effectors have been demonstrated in active anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV), but the timing of complement activation in the autoimmune inflammation remains elusive. This study investigated whether the complement system is activated before onset of symptoms in AAV. METHOD: The Swedish National Patient Register and Cause of Death register were linked to registers of five biobanks to identify individuals sampled before AAV symptom onset. Diagnosis of AAV and time-point for symptom onset were confirmed by reviewing medical records. We identified 64 presymptomatic individuals with serum samples > 1 month < 10 years from AAV symptom onset and 122 matched controls. Complement factors (C2, C5) and activation markers (C5a, C4b) were measured using Luminex technology. RESULTS: Presymptomatic individuals had higher levels of C5 up to 6.5 years before symptom onset, compared with controls [median (IQR) 80.7 (131.9) vs 46.6 (63.4) µg/mL, p = 0.05]. Levels of C5a increased significantly during the pre-dating time (p = 0.033) until symptom onset. The complement levels were significantly higher in presymptomatic myeloperoxidase (MPO)-ANCA+ individuals versus MPO-ANCA- and proteinase-3-ANCA+ individuals. C5 was significantly increased in cases with renal involvement at diagnosis versus controls (p = 0.022), whereas levels of both C5 and C5a were significantly increased in presymptomatic individuals diagnosed with microscopic polyangiitis after onset compared with controls (C5: p = 0.027; C5a: p = 0.027). CONCLUSION: Activation of the complement system is an early event in the pathogenesis of AAV and is mainly associated with MPO-ANCA+ AAV and with microscopic polyangiitis.

Deep phenotyping of facioscapulohumeral muscular dystrophy type 2 by magnetic resonance imaging.

BACKGROUND AND PURPOSE: The aim was to define the radiological picture of facioscapulohumeral muscular dystrophy 2 (FSHD2) in comparison with FSHD1 and to explore correlations between imaging and clinical/molecular data. METHODS: Upper girdle and/or lower limb muscle magnetic resonance imaging scans of 34 molecularly confirmed FSHD2 patients from nine European neuromuscular centres were analysed. T1-weighted and short-tau inversion recovery (STIR) sequences were used to evaluate the global pattern and to assess the extent of fatty replacement and muscle oedema. RESULTS: The most frequently affected muscles were obliquus and transversus abdominis, semimembranosus, soleus and gluteus minimus in the lower limbs; trapezius, serratus anterior, latissimus dorsi and pectoralis major in the upper girdle. Iliopsoas, popliteus, obturator internus and tibialis posterior in the lower limbs and subscapularis, spinati, sternocleidomastoid and levator scapulae in the upper girdle were the most spared. Asymmetry and STIR hyperintensities were consistent features. The pattern of muscle involvement was similar to that of FSHD1, and the combined involvement of trapezius, abdominal and hamstring muscles, together with complete sparing of iliopsoas and subscapularis, was detected in 91% of patients. Peculiar differences were identified in a rostro-caudal gradient, a predominant involvement of lower limb muscles compared to the upper girdle, and in the higher percentage of STIR hyperintensities in FSHD2. CONCLUSION: This multicentre study defines the pattern of muscle involvement in FSHD2, providing useful information for diagnostics and clinical trial design. Both similarities and differences between FSHD1 and FSHD2 were detected, which is also relevant to better understand the pathogenic mechanisms underlying the FSHD-related disease spectrum.

Phenotype and genotype of muscle ryanodine receptor rhabdomyolysis-myalgia syndrome.

OBJECTIVES: Rhabdomyolysis and myalgia are common conditions, and mutation in the ryanodine receptor 1 gene (RYR1) is suggested to be a common cause. Due to the large size of RYR1, however, sequencing has not been widely accessible before the recent advent of next-generation sequencing technology and limited phenotypic descriptions are therefore available. MATERIAL & METHODS: We present the medical history, clinical and ancillary findings of patients with RYR1 mutations and rhabdomyolysis and myalgia identified in Denmark, France and The Netherlands. RESULTS: Twenty-two patients with recurrent rhabdomyolysis (CK > 10 000) or myalgia with hyperCKemia (>1.5 × ULN) and a RYR1 mutation were identified. One had mild wasting of the quadriceps muscle, but none had fixed weakness. Symptoms varied from being restricted to intense exercise to limiting ADL function. One patient developed transient kidney failure during rhabdomyolysis. Two received immunosuppressants on suspicion of myositis. None had episodes of malignant hyperthermia. Muscle biopsies were normal, but CT/MRI showed muscle hypertrophy in most. Delay from first symptom to diagnosis was 12 years on average. Fifteen different dominantly inherited mutations were identified. Ten were previously described as pathogenic and 5 were novel, but rare/absent from the background population, and predicted to be pathogenic by in silico analyses. Ten of the mutations were reported to give malignant hyperthermia susceptibility. CONCLUSION: Mutations in RYR1 should be considered as a significant cause of rhabdomyolysis and myalgia syndrome in patients with the characteristic combination of rhabdomyolysis, myalgia and cramps, creatine kinase elevation, no weakness and often muscle hypertrophy.

Extended exome sequencing identifies BACH2 as a novel major risk locus for Addison's disease.

BACKGROUND: Autoimmune disease is one of the leading causes of morbidity and mortality worldwide. In Addison's disease, the adrenal glands are targeted by destructive autoimmunity. Despite being the most common cause of primary adrenal failure, little is known about its aetiology. METHODS: To understand the genetic background of Addison's disease, we utilized the extensively characterized patients of the Swedish Addison Registry. We developed an extended exome capture array comprising a selected set of 1853 genes and their potential regulatory elements, for the purpose of sequencing 479 patients with Addison's disease and 1394 controls. RESULTS: We identified BACH2 (rs62408233-A, OR = 2.01 (1.71-2.37), P = 1.66 × 10-15 , MAF 0.46/0.29 in cases/controls) as a novel gene associated with Addison's disease development. We also confirmed the previously known associations with the HLA complex. CONCLUSION: Whilst BACH2 has been previously reported to associate with organ-specific autoimmune diseases co-inherited with Addison's disease, we have identified BACH2 as a major risk locus in Addison's disease, independent of concomitant autoimmune diseases. Our results may enable future research towards preventive disease treatment.

Muscle involvement in limb-girdle muscular dystrophy with GMPPB deficiency (LGMD2T).

OBJECTIVE: In this study, muscle involvement assessed by MRI and levels of GMPPB and glycosylation of α-dystroglycan expression in muscle were examined in patients with limb-girdle muscular dystrophy (LGMD) type 2T. METHODS: Six new patients with genetically verified mutations in GMPPB were studied. T1-weighted magnetic resonance images were obtained in 4 participants. Muscle strength and potential involvement of extramuscular organs were examined. Glycosylation of α-dystroglycan in muscle was studied, and GMPPB and α-dystroglycan expression was analyzed by Western blotting. Prevalence of LGMD2T was calculated from the total LGMD population in Denmark. GMPPB was sequenced in all unclassified cases. RESULTS: Two patients carried 3 new mutations in GMPPB. The other 4 patients carried previously described pathogenic mutations in GMPPB. MRI showed that the paraspinal muscles were the most affected, followed by involvement of hamstrings. Our results showed a loss of glycosylation of α-dystroglycan as well as secondary loss of merosin expression on Western blotting. The prevalence of LGMD2T in the Danish cohort of patients with LGMD is 1.5%. CONCLUSIONS: The new findings of this study are (1) the consistent finding of a preferential affection of paraspinal and hamstring muscles in LGMD2T, (2) 3 new mutations in GMPPB, (3) variable loss of glycosylation tested with IIH6 and VIA4 antibodies, and (4) a prevalence of LGMD2T of 1.5% in a well-characterized Danish LGMD cohort.

Endocrine function over time in patients with myotonic dystrophy type 1.

BACKGROUND AND PURPOSE: Patients with myotonic dystrophy type 1 (DM1) have an increased incidence of endocrine dysfunction. In this study, the temporal evolution of endocrine dysfunction in patients with DM1 was investigated. METHODS: Endocrine function was assessed in 68 patients with DM1, in whom endocrine function had been followed, on average, for 8 years. The endocrine function was assessed by measuring the concentration of hormones and metabolites in blood and by validating libido with questionnaires. RESULTS: At baseline, 30 of the 68 patients presented with at least one hormonal dysfunction. When re-evaluated after 8 years, 57 of 68 patients had endocrine dysfunction. Diabetic patients had increased from one to four. At follow-up, hyperparathyroidism occurred in 25% and abnormal thyroid-stimulating hormone in 21%, compared with 14% and 9% at baseline. Sixteen of 33 men had increased luteinizing hormone levels compared with seven at baseline. CONCLUSIONS: Our findings show that endocrine abnormalities amongst patients with DM1 increase over time. Based on these findings it is suggested that correctable endocrine abnormalities should be monitored periodically in this patient group.

Re-evaluation of the dysequilibrium syndrome.

OBJECTIVES: To re-evaluate middle-aged Swedish patients diagnosed with dysequilibrium syndrome (DES) in childhood and to compare their clinical and neuroimaging features to DES with VLDLR gene mutations (DES-VLDR). MATERIALS AND METHODS: Six patients from five families underwent neurological examination and magnetic resonance imaging (MRI) of the brain. Blood samples from the patients were screened for serum carbohydrate-deficient transferrin (s-CDT; disialotransferrin). The very-low-density lipoprotein receptor (VLDLR) gene was sequenced. RESULTS: Five patients had non-progressive cerebellar ataxia (NPCA), dysarthria and short stature. Mental retardation and strabismus, characteristic for DES-VLDLR, were inconsistent among our patients. None of our patients had VLDLR mutations or MRI findings characteristic of DES-VLDLR. MRI findings were variable from a normal cerebellum to marked cerebellar hypoplasia or atrophy and signal intensity changes. One patient was diagnosed with congenital disorder of glycosylation type 1a (CDG-1a). CONCLUSIONS: DES was originally coined on mainly clinical grounds before MRI and specific genetic tests were available, both of which should be used to arrive at an appropriate diagnosis.

Congenital ichthyosis: mutations in ichthyin are associated with specific structural abnormalities in the granular layer of epidermis.

BACKGROUND: Autosomal recessive congenital ichthyosis (ARCI) is a heterogeneous group of skin disorders. Several mutant genes have been identified in ARCI, but the association between genotype and phenotype is poorly understood. METHODS: To investigate genotype-phenotype correlations in ARCI, we selected 27 patients from 18 families with specific ultrastructural features of the epidermis. The characteristic findings using electron microscopy (EM) were abnormal lamellar bodies and elongated membranes in the stratum granulosum, classified as ARCI EM type III. DNA samples from a subset of affected individuals were screened for homozygous genomic regions, and a candidate gene region was identified on chromosome 5q33. The region coincides with the ichthyin gene, previously reported as mutated in ARCI. RESULTS: Mutation screening of ichthyin revealed missense or splice-site mutations in affected members from 16 of 18 (89%) families with characteristics of ARCI EM type III. In a control group of 18 patients with ARCI without EM findings consistent with type III, we identified one patient homozygous for a missense mutation in ichthyin. DISCUSSION: Our findings indicate a strong association between ultrastructural abnormalities in the granular layer of epidermis and ichthyin mutations. The results also suggest that EM provides a tool for specific diagnosis in a genetically homogenous subgroup of patients with ARCI.