Lymphatic disorders caused by mosaic, activating KRAS variants respond to MEK inhibition.

Central conducting lymphatic anomaly (CCLA) due to congenital maldevelopment of the lymphatics can result in debilitating and life-threatening disease with limited treatment options. We identified 4 individuals with CCLA, lymphedema, and microcystic lymphatic malformation due to pathogenic, mosaic variants in KRAS. To determine the functional impact of these variants and identify a targeted therapy for these individuals, we used primary human dermal lymphatic endothelial cells (HDLECs) and zebrafish larvae to model the lymphatic dysplasia. Expression of the p.Gly12Asp and p.Gly13Asp variants in HDLECs in a 2­dimensional (2D) model and 3D organoid model led to increased ERK phosphorylation, demonstrating these variants activate the RAS/MAPK pathway. Expression of activating KRAS variants in the venous and lymphatic endothelium in zebrafish resulted in lymphatic dysplasia and edema similar to the individuals in the study. Treatment with MEK inhibition significantly reduced the phenotypes in both the organoid and the zebrafish model systems. In conclusion, we present the molecular characterization of the observed lymphatic anomalies due to pathogenic, somatic, activating KRAS variants in humans. Our preclinical studies suggest that MEK inhibition should be studied in future clinical trials for CCLA due to activating KRAS pathogenic variants.

Cerebrofacial vascular metameric syndrome is caused by somatic pathogenic variants in PIK3CA.

Disorganized morphogenesis of arteries, veins, capillaries, and lymphatic vessels results in vascular malformations. Most individuals with isolated vascular malformations have postzygotic (mosaic), activating pathogenic variants in a handful of oncogenes within the PI3K-RAS-MAPK pathway (Padia et al., Laryngoscope Investig Otolaryngol 4: 170-173 [2019]). Activating pathogenic variants in the gene PIK3CA, which encodes for the catalytic subunit of phosphatidylinositol 3-kinase, are present in both lymphatic and venous malformations as well as arteriovenous malformations in other complex disorders such as CLOVES syndrome (congenital, lipomatous, overgrowth, vascular malformations, epidermal anevi, scoliosis) (Luks et al., Pediatr Dev Pathol 16: 51 [2013]; Luks et al., J Pediatr 166: 1048-1054.e1-5 [2015]; Al-Olabi et al., J Clin Invest 128: 1496-1508 [2018]). These vascular malformations are part of the PIK3CA-related overgrowth spectrum, a spectrum of entities that have regionalized disordered growth due to the presence of tissue-restricted postzygotic PIK3CA pathogenic variants (Keppler-Noreuil et al., Am J Med Genet A 167A: 287-295 [2015]). Cerebrofacial vascular metameric syndrome (CVMS; also described as cerebrofacial arteriovenous metameric syndrome, Bonnet-Dechaume-Blanc syndrome, and Wyburn-Mason syndrome) is the association of retinal, facial, and cerebral vascular malformations (Bhattacharya et al., Interv Neuroradiol 7: 5-17 [2001]; Krings et al., Neuroimaging Clin N Am 17: 245-258 [2007]). The segmental distribution, the presence of tissue overgrowth, and the absence of familial recurrence are all consistent with CVMS being caused by a postzygotic mutation, which has been hypothesized by previous authors (Brinjiki et al., Am J Neuroradiol 39: 2103-2107 [2018]). However, the genetic cause of CVMS has not yet been described. Here, we present three individuals with CVMS and mosaic activating pathogenic variants within the gene PIK3CA We propose that CVMS be recognized as part of the PIK3CA-related overgrowth spectrum, providing justification for future trials using pharmacologic PIK3CA inhibitors (e.g., alpelisib) for these difficult-to-treat patients.

Misdiagnosis of capillary malformations in darker skin phototypes.

In the dermatologic medical literature, there is an underrepresentation of conditions in individuals of color. Due to the lack of representation, it may be harder for clinicians to recognize certain diagnoses in patients with darker skin phototypes leading to misdiagnosis and affecting overall patient management, outcomes, and satisfaction. Here, we present four Black or Indigenous People of Color who were initially referred for hyperpigmentation, hemihyperplasia, or café au lait spots and found to have syndromic capillary malformations.

Variants in the degron of AFF3 are associated with intellectual disability, mesomelic dysplasia, horseshoe kidney, and epileptic encephalopathy.

The ALF transcription factor paralogs, AFF1, AFF2, AFF3, and AFF4, are components of the transcriptional super elongation complex that regulates expression of genes involved in neurogenesis and development. We describe an autosomal dominant disorder associated with de novo missense variants in the degron of AFF3, a nine amino acid sequence important for its binding to ubiquitin ligase, or with de novo deletions of this region. The sixteen affected individuals we identified, along with two previously reported individuals, present with a recognizable pattern of anomalies, which we named KINSSHIP syndrome (KI for horseshoe kidney, NS for Nievergelt/Savarirayan type of mesomelic dysplasia, S for seizures, H for hypertrichosis, I for intellectual disability, and P for pulmonary involvement), partially overlapping the AFF4-associated CHOPS syndrome. Whereas homozygous Aff3 knockout mice display skeletal anomalies, kidney defects, brain malformations, and neurological anomalies, knockin animals modeling one of the microdeletions and the most common of the missense variants identified in affected individuals presented with lower mesomelic limb deformities like KINSSHIP-affected individuals and early lethality, respectively. Overexpression of AFF3 in zebrafish resulted in body axis anomalies, providing some support for the pathological effect of increased amount of AFF3. The only partial phenotypic overlap of AFF3- and AFF4-associated syndromes and the previously published transcriptome analyses of ALF transcription factors suggest that these factors are not redundant and each contributes uniquely to proper development.

Cervical spinal cord compression in infants with achondroplasia: should neuroimaging be routine?

PURPOSE: To examine results of magnetic resonance imaging (MRI), polysomnograms (PSG), and patient outcomes in patients with achondroplasia in light of recent screening recommendations for infants with achondroplasia. METHODS: We reviewed medical records of 49 patients with achondroplasia followed at our institution between September 1997 and January 2017, including physical exams, MRIs, PSGs (when available), and surgical histories. Appropriate PSG data were available for 39 of these patients. RESULTS: Twenty-seven of 49 patients had cervical cord compression on MRI, and 20 of those patients required surgery. Central apnea was detected in 2/23 patients with cervical cord compression in whom PSG data was available. Physical exam revealed depressed deep-tendon reflexes in two patients with cord compression and one patient without cord compression. Besides hypotonia in some, the neurological exams of these patients were unremarkable. CONCLUSIONS: Cervical cord compression is a common occurrence in infants with achondroplasia and necessitates surgical intervention in some patients. Physical exam and PSG are poor predictors of the presence of cord compression or the need for surgery. All infants with achondroplasia should have MRIs of the craniocervical junction in the first 6 months of life.

Ocular findings in a patient with oculofaciocardiodental (OFCD) syndrome and a novel BCOR pathogenic variant.

PURPOSE: To report a case of OFCD associated with a de novo BCOR pathogenic variant and highlight the ocular findings and possible mechanisms. METHODS: A retrospective chart review of the patient's ocular and systemic findings was performed. The patient underwent diagnostic whole exome sequencing (WES). RESULTS: The patient had a comprehensive eye exam in infancy demonstrating bilateral congenital cataracts consisting of posterior lenticonus with a posterior cortical opacity. She also had blepharoptosis with a hooded appearance and retinal pigment hypertrophy of the inferior retina bilaterally. Systemic findings include atrial septal defect, patent ductus arteriosus, congenital clubfoot, syndactyly, tethered cord, and laryngeal cleft. WES identified a de novo heterozygous R1136X pathogenic variant in the BCOR gene. CONCLUSION: The typical ocular manifestation of OFCD syndrome is congenital cataracts, which can have a significant impact on visual development and so should be considered in patients with multiple medical issues that may fit the diagnosis. A comprehensive eye exam in these patients is thus warranted.