Background: Macrocephaly can be a component manifestation of several monogenic conditions, in association with intellectual disability/developmental delay (ID/DD) behaviour abnormalities, including autism spectrum disorders (ASD), and variable additional features. On the other hand, idiopathic ASD can present with developmental delay and macrocephaly. Methods: We carried out a retrospective analysis of a cohort of 78 patients who were tested from February 2017 to December 2024 by high-throughput sequencing of a panel of 27 genes (ABCC9, AKT1, AKT2, AKT3, BRWD3, DIS3L2, DNMT3A, EZH2, GPC3, GPC4, HERC1, MED12, MTOR, NFIA, NFIX, NSD1, PDGFRB, PIK3CA, PIK3R1, PIK3R2, PPP2R1A, PPP2R5D, PTEN, RAB39B, RNF135, SETD2, and TBC1D7) because of neurodevelopmental impairment, including ID/DD, ASD/behaviour abnormalities associated with macrocephaly, mimicking to a large extent idiopathic ASD. Results: Pathogenic variants leading to the diagnosis of monogenic conditions were detected in 22 patients (28%), including NSD1 (2), PTEN (16), and PPP2R5D (4). Distinctive of the PTEN-associated phenotype were true macrocephaly (100%), ASD or behaviour abnormalities (92%), mild/borderline ID (79%), and no facial dysmorphisms. Typical of the PPP2R5D-associated phenotype were relative macrocephaly (75%), a few unspecific peculiar facial characteristics (50%), and a more variable presentation of the neurodevelopmental phenotype. Conclusions: Pathogenic variants in PTEN and PPP2R5D are the most recurrent gene mutations in a patient-oriented procedure for the genetic diagnosis of apparently idiopathic ASD and behaviour abnormalities associated with macrocephaly. The clinical applicability of the presented diagnostic strategy is discussed.

We describe the complex case of a 44-year-old man with polycystic kidney disease, mild cognitive impairment, and tremors in the upper limbs. Brain MRI showed lesions compatible with leukodystrophy. The diagnostic process, which included clinical exome sequencing (CES) and chromosomal microarray analysis (CMA), revealed a triple diagnosis: autosomal dominant polycystic kidney disease (ADPKD) due to a pathogenic variant, c.2152C>T-p.(Gln718Ter), in the PKD1 gene; late-onset phenylketonuria due to the presence of two missense variants, c.842C>T-p.(Pro281Leu) and c.143T>C-p.(Leu48Ser) in the PAH gene; and a 915 Kb duplication on chromosome 15. Few patients with multiple concurrent genetic diagnoses are reported in the literature; in this ADPKD patient, genome-wide analysis allowed for the diagnosis of adult-onset phenylketonuria (which would have otherwise gone unnoticed) and a 15q11.2 duplication responsible for cognitive and behavioral impairment with incomplete penetrance. This case underlines the importance of clinical genetics for interpreting complex results obtained by genome-wide techniques, and for diagnosing concurrent late-onset monogenic conditions.

Richard Peto’s paradox, first described in 1975 from an epidemiological perspective, established an inverse correlation between the probability of developing cancer in multicellular organisms and the number of cells. Larger animals exhibit fewer tumors compared to smaller ones, though exceptions exist. Mice are more susceptible to cancer than humans, while elephants and whales demonstrate significantly lower cancer prevalence rates than humans. How nature and evolution have addressed the issue of cancer in the animal kingdom remains largely unexplored. In the field of medicine, much attention has been devoted to cancer-predisposing genes, as they offer avenues for intervention, including blocking, downregulating, early diagnosis, and targeted treatment. Predisposing genes also tend to manifest clinically earlier and more aggressively, making them easier to identify. However, despite significant strides in modern medicine, the role of protective genes lags behind. Identifying genes with a mild predisposing effect poses a significant challenge. Consequently, comprehending the protective function conferred by genes becomes even more elusive, and their very existence is subject to questioning. While the role of variable expressivity and penetrance defects of the same variant in a family is well-documented for many hereditary cancer syndromes, attempts to delineate the function of protective/modifier alleles have been restricted to a few instances. In this review, we endeavor to elucidate the role of protective genes observed in the animal kingdom, within certain genetic syndromes that appear to act as cancer-resistant/repressor alleles. Additionally, we explore the role of protective alleles in conditions predisposing to cancer. The ultimate goal is to discern why individuals, like Winston Churchill, managed to live up to 91 years of age, despite engaging in minimal physical activity, consuming large quantities of alcohol daily, and not abstaining from smoking.

The ABCB11 gene encodes for the bile salt export pump (BSEP)—the main exporter of bile acids expressed on the canalicular membrane of the hepatocyte [ 1–3]. Pathogenic variants in the ABCB11 gene can lead to a range of clinical conditions. These conditions vary from benign recurrent intrahepatic cholestasis type 2 (BRIC2), which is a non-severe disorder characterized by occasional episodes of low levels of gamma-glutamyl transferase (GGT) cholestasis, to progressive familial intrahepatic cholestasis type 2 (PFIC2), which is more severe and may necessitate liver transplantation. Recently, odevixibat—an inhibitor of the ileal bile acid transporter—was able to reduce itching and serum bile acid concentrations in a randomized–controlled study, including patients with PFIC2. Odevixibat provide treatment benefits in a disease with high unmet medical needs [ 4].