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Spondyloenchondrodysplasia (SPENCD) is a rare skeletal dysplasia, characterized by metaphyseal lesions, neurological impairment and immune dysregulation associated with lupus-like features. SPENCD is caused by biallelic mutations in the ACP5 gene encoding tartrate-resistant phosphatase. We report on a child, who presented with spasticity, multisystem inflammation, autoimmunity and immunodeficiency with minimal metaphyseal changes due to compound heterozygosity for two novel ACP5 mutations. These findings extend the phenotypic spectrum of SPENCD and indicate that ACP5 mutations can cause severe immune dysregulation and neurological impairment even in the absence of metaphyseal dysplasia.
Hyper-IgM syndrome type 2 (HIGM2) is a B cell intrinsic primary immunodeficiency caused by mutations in AICDA encoding activation-induced cytidine deaminase (AID) which impair immunoglobulin class switch recombination (CSR) and somatic hypermutation (SHM). Whereas autosomal-recessive AID-deficiency (AR-AID) affects both CSR and SHM, the autosomal-dominant form (AD-AID) due to C-terminal heterozygous variants completely abolishes CSR but only partially affects SHM. AR-AID patients display enhanced germinal center (GC) reactions and autoimmune manifestations, which are not present in AD-AID, suggesting that SHM but not CSR regulates GC reactions and peripheral B cell tolerance. Herein, we describe two siblings with HIGM2 due to a novel homozygous AICDA mutation (c.428-1G > T) which disrupts the splice acceptor site of exon 4 and results in the sole expression of a truncated AID variant that lacks 10 highly conserved amino acids encoded by exon 4 (AID-ΔE4a). AID-ΔE4a patients suffered from defective CSR and enhanced GC reactions and were therefore indistinguishable from other AR-AID patients. However, the AID-ΔE4a variant only partially affected SHM as observed in AD-AID patients. In addition, AID-ΔE4a but not AD-AID patients revealed impaired targeting of mutational hotspot motives and distorted mutational patterns. Hence, qualitative defects in AID function and altered SHM rather than global decreased SHM activity may account for the disease phenotype in these patients.
Background
Chronic non-bacterial osteomyelitis (CNO) is an autoinflammatory disorder of the skeletal system of yet unknown etiology. Patients present with local bone pain and inflammation and - to our experience - often suffer from functional impairment with significant disabilities of daily life. The objective of this study was to assess physical activity, fitness and health-related quality of life (HRQOL) in adolescents with established diagnosis of CNO versus healthy controls (HC).
Methods
15 patients with CNO and 15 age and gender matched HC aged 13–18 years, completed questionnaires, performed an incremental exercise test with gas exchange measures up to voluntary fatigue and wore an accelerometer over 7 days at home to assess physical activity behavior.
Results
At the time of assessment, 5 CNO patients were in clinical, one in radiological and 5 in clinical and radiological remission. 7 did not receive any therapy at the time of assessment. The results of the exercise test and of the accelerometry did not show any significant difference between CNO and HC. However, reported sports participation was lower in patients with CNO and PedsQL3.0 and 4.0 showed significant lower values in most of the scores indicating reduced HRQOL.
Conclusion
Although most CNO patients showed a favorable course of disease without any relevant differences in objective measurements of physical activity and fitness versus HC at the time of assessment, questionnaires revealed perceived limitations. Further studies are needed to measure HRQOL and to validate questionnaires in patients with CNO against objective measures including more participants with a higher level of disease activity.