Although rare, COVID-19 in children may lead to hospitalization due to severe respiratory symptoms, or a hyperinflammatory state called Multisystem Inflammatory Syndrome in Children (MIS-C). This study examined respiratory morbidity in children 5 to 12 months after hospitalization for MIS-C or COVID-19. In this multi-center, prospective cohort study, children (0-17 years) with a history of hospitalization for MIS-C or COVID-19 in Dutch hospitals were invited for follow-up. Visits were scheduled in one of three academic hospitals, to evaluate current clinical status and health-related quality of life (HRQoL), and perform lung function tests and cardiopulmonary exercise testing (CPET). 72 children were included (43 MIS-C, 29 COVID-19), of whom 19% (5% and 41%, respectively) reported long-term respiratory symptoms including dyspnea and cough, a median of 8 months after hospitalization. Fatigue was the most common non-respiratory symptom. HRQoL was more frequently (60%) impaired in the COVID-19 group than the MIS-C group (14%). Spirometry (n = 48) and CPET (n = 40) were conducted in children aged > 4 and > 6 years, respectively. Spirometry was abnormal in 15% of the MIS-C group and 44% of COVID-19 group, CPET in 41% and 75%, respectively. Deconditioning patterns were the most common reason (30%) for abnormal CPET results. Long-term respiratory sequelae and fatigue occurred after both MIS-C and severe COVID-19, but respiratory symptoms and impaired HRQoL were more frequent after COVID-19. Lung function and CPET abnormalities in children with COVID-19 often corresponded with symptoms. Children with MIS-C often showed CPET abnormalities without respiratory complaints or lung function changes.

Autoimmune encephalitis can be classified into antibody-defined subtypes, which can manifest with immunotherapy-responsive movement disorders sometimes mimicking non-inflammatory aetiologies. In the elderly, anti-LGI1 and contactin associated protein like 2 (CASPR2) antibody-associated diseases compose a relevant fraction of autoimmune encephalitis. Patients with LGI1 autoantibodies are known to present with limbic encephalitis and additionally faciobrachial dystonic seizures may occur. However, the clinical spectrum of CASPR2 autoantibody-associated disorders is more diverse including limbic encephalitis, Morvan's syndrome, peripheral nerve hyperexcitability syndrome, ataxia, pain and sleep disorders. Reports on unusual, sometimes isolated and immunotherapy-responsive movement disorders in CASPR2 autoantibody-associated syndromes have caused substantial concern regarding necessity of autoantibody testing in patients with movement disorders. Therefore, we aimed to systematically assess their prevalence and manifestation in patients with CASPR2 autoimmunity. This international, retrospective cohort study included patients with CASPR2 autoimmunity from participating expert centres in Europe. Patients with ataxia and/or movement disorders were analysed in detail using questionnaires and video recordings. We recruited a comparator group with anti-LGI1 encephalitis from the GENERATE network. Characteristics were compared according to serostatus. We identified 164 patients with CASPR2 autoantibodies. Of these, 149 (90.8%) had only CASPR2 and 15 (9.1%) both CASPR2 and LGI1 autoantibodies. Compared to 105 patients with LGI1 encephalitis, patients with CASPR2 autoantibodies more often had movement disorders and/or ataxia (35.6 versus 3.8%; P < 0.001). This was evident in all subgroups: ataxia 22.6 versus 0.0%, myoclonus 14.6 versus 0.0%, tremor 11.0 versus 1.9%, or combinations thereof 9.8 versus 0.0% (all P < 0.001). The small group of patients double-positive for LGI1/CASPR2 autoantibodies (15/164) significantly more frequently had myoclonus, tremor, 'mixed movement disorders', Morvan's syndrome and underlying tumours. We observed distinct movement disorders in CASPR2 autoimmunity (14.6%): episodic ataxia (6.7%), paroxysmal orthostatic segmental myoclonus of the legs (3.7%) and continuous segmental spinal myoclonus (4.3%). These occurred together with further associated symptoms or signs suggestive of CASPR2 autoimmunity. However, 2/164 patients (1.2%) had isolated segmental spinal myoclonus. Movement disorders and ataxia are highly prevalent in CASPR2 autoimmunity. Paroxysmal orthostatic segmental myoclonus of the legs is a novel albeit rare manifestation. Further distinct movement disorders include isolated and combined segmental spinal myoclonus and autoimmune episodic ataxia.

Autoimmune polyendocrinopathy-candidiasis-ectodermal-dystrophy (APECED) or autoimmune polyglandular syndrome Type 1 is a rare autosomal recessive syndrome. The disorder is caused by mutations in the AIRE (AutoImmune Regulator) gene. According to the classic criteria, clinical diagnosis requires the presence of at least two of three main components: chronic mucocutaneous candidiasis, hypoparathyroidism and primary adrenal insufficiency. Furthermore, patients are often affected by other endocrine or non-endocrine associated autoimmune conditions. The enrichment of the non-classical triad seems to occur differently in different cohorts. Screenings of the population revealed that homozygous AIRE mutations c.769C > T, c.415C > T and c.254A > G have a founder effect in Finnish, Sardinian and Iranian Jew populations respectively. We report here the clinical and genetic characteristics of two new Serbian APECED siblings, one male and one female, actual age of 27 and 24 respectively, born from non-consanguineous parents. Addison's disease was diagnosed in the male at the age of 3.5 and hypoparathyroidism at the age of 4. The female developed hypoparathyroidism at 4 years of age. She presented diffuse alopecia, madarosis, onychomycosis, teeth enamel dysplasia. She further developed Addison's disease at the age of 11 and Hashimoto's thyroiditis at the age of 13.5. She had menarche at the age of 14 but developed autoimmune oophoritis and premature ovarian failure at the age of 16. A treatment with hydrocortisone, fludrocortisone and alfacalcidiol was established for both siblings; L-T4 (levo-thyroxine) for thyroid dysfunction and levonorgestrel and etinilestradiol for POF were also administered to the female. Genetic screening revealed a homozygous c.769C > T (R257X (p.Arg257X)) AIRE mutation. We additionally reviewed the literature on 11 previously published Serbian patients and evaluated the frequency of their main diseases in comparison to Finnish, Sardinian, Turkish, Indian and North/South American cohorts. A founder effect was discovered for the R257X genotype detected in the DNA of 10 homozygous and 2 heterozygous patients. Of note, all Serbian APECED patients were affected by adrenal insufficiency and 10 out of 13 patients presented CMC.

ANA are the most extensively used test for the diagnosis of systemic autoimmune diseases. However, testing by indirect immunofluorescence assays (IIFAs) on HEp-2 cells, the gold standard test, is time-consuming and needs expertise. Thus there is a trend to replace it with other automated solid-phase assays directed against specific ANA. Nonetheless, the Hep-2 cell is an autoantigen array and ANA have been classified into 29 types, some of them with no clear association with a specificity to be detected. It is especially in these uncommon patterns where no clinical relationship is found and no antigenic specificity is detected. Here we retrospectively collected clinical data from patients with confirmed uncommon HEp-2 IIFA patterns to search for an associated clinical condition. We conducted an observational retrospective study including 608 patients with organ-specific and non-organ-specific autoimmune diseases (OSADs and NOSADs, respectively) with a confirmed rare pattern of ANA detected by IIFA on HEp-2 cells in the routine practice of the Spanish European Autoantibodies Standardization Initiative laboratories. Inclusion criteria are the existence of a minimum follow-up of 2 years and the availability of clinical data. Nuclear patterns were more frequent in SLE (P = 0.001) and SS (P = 0.001), whereas the cytoplasmic ones were significantly higher in SSc (P = 0.022) and inflammatory myositis (P = 0.016). Mitotic patterns did not show any preferences for a specific disease and 62.7% of them corresponded to the nuclear mitotic apparatus pattern (AC-26). The most frequent NOSADs in patients with the AC-26 pattern were SLE (28.6%), SS (11.9%) and RA (11.9%). The cytoplasmic HEp-2 IIFA patterns were equally distributed in both groups of patients. In the OSAD patients there was no predominant pattern, except for AC-6 in primary biliary cholangitis due to Sp-100 antibodies (P < 0.001). Detection of infrequent ANA might be a unique finding with no disease-associated specificities and could lead to the suspicion of an autoimmune disease.

To report the prevalence of anti-neuronal antibodies in a prospective whole-nation cohort of children presenting with seizures before their third birthday. This was a prospective population-based national cohort study involving all children presenting with new-onset epilepsy or complex febrile seizures before their third birthday over a 3-year period. Patients with previously identified structural, metabolic, or infectious cause for seizures were excluded. Serum samples were obtained at first presentation and tested for 7 neuronal antibodies using live cell-based assays. Clinical data were collected with structured proformas at recruitment and 24 months after presentation. In addition, patients with seizures and clinically suspected autoimmune encephalitis were independently identified by a review of the case records of all children <3 years of age in Scotland who had undergone EEG. Two hundred ninety-eight patients were identified and recruited and underwent autoantibody testing. Antibody positivity was identified in 18 of 298 (6.0%). The antibodies identified were GABA receptor B (n = 8, 2.7%), contactin-associated protein 2 (n = 4, 1.3%), glycine receptor (n = 3, 1.0%), leucine-rich glioma inactivated 1 (n = 2, 0.7%), NMDA receptor (n = 1, 0.3%), and GABA receptor A (n = 1, 0.3%). None of these patients had a clinical picture of autoimmune encephalitis. Seizure classification and clinical phenotype did not correlate with antibody positivity. Autoimmune encephalitis is very rare in early childhood. However serum neuronal antibodies are identified in 6.4% of children presenting with seizures at <3 years of age. Antibody testing should not be a routine clinical test in early childhood-onset epilepsy because, in the absence of other features of autoimmune encephalitis, antibody positivity is of doubtful clinical significance. Antibody testing should be reserved for patients with additional features of encephalitis.