Objective: The most common presentation of Klinefelter syndrome (KS) is infertility and features of hypogonadism. Currently no consensus exists on the risk of malignancy in this syndrome. Several case reports show an incidence of extragonadal germ cells tumors (eGCT) of 1.5 per 1000 KS patients (OR 50 against healthy population). Malignant germ cell tumors are rare in children. They account for 3% of all children cancers. Young patients with a germ cell tumor are not routinely tested for Klinefelter syndrome. This can therefore result in underdiagnosing. Literature data suggest a correlation between eGCT and KS. To the best of our knowledge there is no precise description of the primary locations of germ cell tumors in KS patients. The purpose of this study is to evaluate age groups and primary locations of extragonadal germ cell tumors in Klinefelter patients. With this data we investigate whether it is necessary to perform a cytogenetic analysis for KS in every eGCT patient. Study design: This study is based on case report publications in PubMed/Medline published until march 2020 that described “Klinefelter Syndrome (MeSH) AND/OR extragonadal germ cell tumors”. Publications were included when patients age, location and histology of the germ cell tumor was known. Two double blinded reviewers selected the studies.Results: 141 KS patients with eGCTs were identified. Mean age at presentation was 17.3 years (StDev + − 10.2). In contrast to the extragonadal germ cell tumors in adults, most eGCT in children were mediastinal or in the central nervous system (respectively 90/141; 64% and 23/141; 16% of all tumors). Distribution of histologic subtypes showed that the largest fraction represented a teratoma, mixed-type-non-seminomateus GCT and germinoma, respectively 34/141; 24%, 26/141; 18% and 20/141; 14% of all tumors. Conclusion: These data suggest a correlation between primary extragonadal germ cell tumors and Klinefelter syndrome. There appears to be an indication for screening on KS in young patients with an eGCT in the mediastinum. A low threshold for radiologic examinations should be considered to discover eGCT. We emphasize the need for genetic analysis in all cases of a male with a mediastinal germ cell tumor for the underdiagnosed Klinefelter syndrome.

Key Clinical Message: 22q11.2DS is a significant health problem because of its fairly high incidence. It is relevant to be vigilant regarding the diagnosis of cancer amongst 22q11.2 patients as there might be an increased risk, especially amongst patients with the 22q11.2 distal deletion syndrome.

Key Clinical Message: Glucose‐6‐phosphate (G6PD) deficiency is the most common human enzyme defect, often presenting with neonatal jaundice and/or acute hemolytic anemia, triggered by oxidizing agents. G6PD deficiency is an X‐linked, hereditary disease, mainly affecting men, but should also be considered in females with an oxidative hemolysis.

Imerslund-Gräsbeck syndrome (IGS) is a rare autosomal recessive disorder characterized by vitamin B12 malabsorption. Most patients present with non-specific symptoms attributed to vitamin B12 deficiency, and proteinuria. Patients may if untreated, develop severe neurocognitive manifestations. If recognized and treated with sufficient doses of vitamin B12, patients recover completely. We provide, for the first time, an overview of all previously reported cases of IGS. In addition, we provide a complete review of IGS and describe two new patients.

Background: It is not uncommon that an infant with a disease of unknown etiology is presented to a physician. Facial dysmorphic features lead to a different diagnosis. It is a challenge to link the presentation to the newfound diagnosis. Case presentation: A 37-day-old Yemenite Jewish girl was presented to our institution with a clinical picture of pseudohypoaldosteronism due to abnormal facial features and a psychomotor developmental delay. Further investigation led to the diagnosis of CDK13-related disorder. According to the literature, CDK13 has a key role in the cell cycle, but no interference with the aldosterone signaling pathway or electrolyte balance was described. No mutations in the previously described gene NR3C2 (cytogenetic location 4q31.23), encoding the mineralocorticoid receptor, were found. Although the clinical presentation corresponded to pseudohypoaldosteronism type 1, we could not genetically confirm this. Conclusions: Probably pseudohypoaldosteronism was a coincidental finding in this girl with a CDK13 mutation, but because only limited information is known about CDK13-related disorders, further investigation could be more informative to clarify this presentation.