World-Renowned "Swiss" Pediatricians, Their Syndromes, and Matching Imaging Findings: A Historical Perspective

The goal of this manuscript is to present and summarize several rare pediatric syndromes (Zellweger syndrome, Kartagener syndrome, Prader-Willi syndrome, Schinzel-Giedion syndrome, Fanconi anemia, Joubert-Boltshauser syndrome, Poretti-Boltshauser syndrome, and Langer-Giedion syndrome) who have been named after luminary "Swiss" physicians (pediatricians, pediatric neurologists, or pediatric radiologists) who recognized, studied, and published these syndromes. In this manuscript, a brief historical summary of the physicians is combined with the key clinical symptoms at presentation and the typical imaging findings. This manuscript is not aiming to give a complete comprehensive summary of the syndromes, nor does it ignore the valuable contributions of many "Swiss" scientists who are not included here, but focuses on several rare syndromes that benefit from imaging data.

Case Report: Zellweger Syndrome and Humoral Immunodeficiency: The Relevance of Newborn Screening for Primary Immunodeficiency

BACKGROUND

Zellweger syndrome (ZS) is a congenital autosomal recessive disease within the spectrum of peroxisome biogenesis disorders, characterized by the impairment of peroxisome assembly. The presence of peroxisome enzyme deficiencies leads to complex developmental sequelae, progressive disabilities, and multiorgan damage, due to intracellular accumulation of very-long-chain fatty acids (VLCFAs).

CASE PRESENTATION

We report the case of an infant affected by ZS in which agammaglobulinemia, detected through neonatal screening of congenital immunodeficiencies, appeared as a peculiar trait standing out among all the other classical characteristics of the syndrome. The exome analysis through next-generation sequencing (NGS), which had previously confirmed the diagnostic suspicion of ZS, was repeated, but no mutations causative of inborn error of immunity (humoral defect) were detected.

CONCLUSION

In this case, no genetic variants accountable for the abovementioned agammaglobulinemia were detected. Given that the scientific literature reports the involvement of peroxisomes in the activation of Nuclear Factor κ-light-chain-enhancer of activated B cells (NF-κB) pathway, which is crucial for B-cell survival, with this work, we hypothesize the existence of a link between ZS and humoral immunodeficiencies. Further studies are required to confirm this hypothesis.

Peroxisomal Disorders and Their Mouse Models Point to Essential Roles of Peroxisomes for Retinal Integrity

Peroxisomes are multifunctional organelles, well known for their role in cellular lipid homeostasis. Their importance is highlighted by the life-threatening diseases caused by peroxisomal dysfunction. Importantly, most patients suffering from peroxisomal biogenesis disorders, even those with a milder disease course, present with a number of ocular symptoms, including retinopathy. Patients with a selective defect in either peroxisomal α- or β-oxidation or ether lipid synthesis also suffer from vision problems. In this review, we thoroughly discuss the ophthalmological pathology in peroxisomal disorder patients and, where possible, the corresponding animal models, with a special emphasis on the retina. In addition, we attempt to link the observed retinal phenotype to the underlying biochemical alterations. It appears that the retinal pathology is highly variable and the lack of histopathological descriptions in patients hampers the translation of the findings in the mouse models. Furthermore, it becomes clear that there are still large gaps in the current knowledge on the contribution of the different metabolic disturbances to the retinopathy, but branched chain fatty acid accumulation and impaired retinal PUFA homeostasis are likely important factors.

Structural Mapping of Missense Mutations in the Pex1/Pex6 Complex

Peroxisome biogenesis disorders (PBDs) are nontreatable hereditary diseases with a broad range of severity. Approximately 65% of patients are affected by mutations in the peroxins Pex1 and Pex6. The proteins form the heteromeric Pex1/Pex6 complex, which is important for protein import into peroxisomes. To date, no structural data are available for this AAA+ ATPase complex. However, a wealth of information can be transferred from low-resolution structures of the yeast scPex1/scPex6 complex and homologous, well-characterized AAA+ ATPases. We review the abundant records of missense mutations described in PBD patients with the aim to classify and rationalize them by mapping them onto a homology model of the human Pex1/Pex6 complex. Several mutations concern functionally conserved residues that are implied in ATP hydrolysis and substrate processing. Contrary to fold destabilizing mutations, patients suffering from function-impairing mutations may not benefit from stabilizing agents, which have been reported as potential therapeutics for PBD patients.

Peroxisomal Disorders and Retinal Degeneration

Peroxisomal disorders are a group of inherited metabolic diseases, which can be incompatible with life in the postnatal period or allow survival into adulthood. Retinopathy is a recurrent feature in both the severely and mildly affected patients, which can be accompanied with other ophthalmological pathologies. Thanks to next-generation sequencing, patients originally identified with other inherited blinding diseases were reclassified as suffering from peroxisomal disorders. In addition, new peroxisomal gene defects or disease presentations exhibiting retinal degeneration were recently identified. The pathogenic mechanisms underlying retinopathy in peroxisomal disorders remain unresolved.

Defining the genetic basis of early onset hereditary spastic paraplegia using whole genome sequencing

We performed whole genome sequencing (WGS) in nine families from India with early-onset hereditary spastic paraplegia (HSP). We obtained a genetic diagnosis in 4/9 (44 %) families within known HSP genes (DDHD2 and CYP2U1), as well as perixosomal biogenesis disorders (PEX16) and GM1 gangliosidosis (GLB1). In the remaining patients, no candidate structural variants, copy number variants or predicted splice variants affecting an extended candidate gene list were identified. Our findings demonstrate the efficacy of using WGS for diagnosing early-onset HSP, particularly in consanguineous families (4/6 diagnosed), highlighting that two of the diagnoses would not have been made using a targeted approach.

Zellweger syndrome: an older child with progressive foot deformity

Zellweger spectrum disorders result from defects in the assembly of the peroxisome and are sometimes referred to as peroxisome biogenesis disorders. Orthopedic manifestations of this condition are variable. This case report illustrates an ambulatory child with Zellweger syndrome and progressive foot deformity. The course of treatment consisted of initial soft tissue surgery, early recurrence of the deformity, followed by successful arthrodesis.