Combined capillary-venous-lymphatic malformations without overgrowth in patients with Klippel-Trénaunay syndrome

Segmental undergrowth is associated with pathogenic variants in vascular malformation genes: A retrospective case-series study

Segmental overgrowth has been widely described in patients with congenital vascular anomalies. However, segmental undergrowth has been poorly characterized, and no large series of patients have been published. We present the clinical and molecular characteristics a cohort of 37 patients with vascular malformations and segmental undergrowth. True undergrowth was only considered when the musculoskeletal system was involved to avoid confusion with other causes of segmental reduction, as in lipodystrophy or the long-term osteopenia seen in patients with Servelle-Martorell syndrome. Deep high-throughput sequencing was performed in tissue samples from 20 patients using a custom panel. We identified three groups: undergrowth associated with (1) venous, (2) capillary-venous, and (3) lymphatic-capillary-venous malformations. Congenital or early childhood onset undergrowth can occur with or without associated overgrowth. Different likely pathogenic or pathogenic variants were detected in 13 of 20 (65%) tissue samples in the PIK3CA, TEK, GNAQ, or GNA11 genes. In conclusion, the eponymous Servelle-Martorell syndrome should not be used as a synonym for undergrowth. Segmental undergrowth should be considered a characteristic associated with vascular malformations. Patients with PIK3CA variants show all different combinations of overgrowth and undergrowth. Thus, the term PROS (PIK3CA-related overgrowth spectrum) does not cover the entire spectrum.

Imaging of benign cervicofacial vascular anomalies and associated syndromes

Cervicofacial vascular anomalies can result in morbidity, pain, and cosmetic concerns in affected individuals. Each anomaly has its own unique natural history, treatment, and associations with underlying genetic syndromes. For optimal patient care, it is important for the neuroradiologist to accurately recognize and characterize these entities to ensure appropriate treatment and management. In this review, we discuss the general characteristics, classifications, and imaging features associated with the most common vascular anomalies such as hemangiomas, arteriovenous malformations and fistulas, capillary malformations, venous malformations, and lymphatic malformations in the context of associated syndromes. Additionally, we discuss novel imaging techniques that aid in identifying these vascular anomalies.

A review of mechanisms of disease across PIK3CA-related disorders with vascular manifestations

BACKGROUND

PIK3CA-related disorders include vascular malformations and overgrowth of various tissues that are caused by postzygotic, somatic variants in the gene encoding phosphatidylinositol-3-kinase (PI3K) catalytic subunit alpha. These mutations result in activation of the PI3K/AKT/mTOR signaling pathway. The goals of this review are to provide education on the underlying mechanism of disease for this group of rare conditions and to summarize recent advancements in the understanding of, as well as current and emerging treatment options for PIK3CA-related disorders.

MAIN BODY

PIK3CA-related disorders include PIK3CA-related overgrowth spectrum (PROS), PIK3CA-related vascular malformations, and PIK3CA-related nonvascular lesions. Somatic activating mutations (predominantly in hotspots in the helical and kinase domains of PIK3CA, but also in other domains), lead to hyperactivation of the PI3K signaling pathway, which results in abnormal tissue growth. Diagnosis is complicated by the variability and overlap in phenotypes associated with PIK3CA-related disorders and should be performed by clinicians with the required expertise along with coordinated care from a multidisciplinary team. Although tissue mosaicism presents challenges for confirmation of PIK3CA mutations, next-generation sequencing and tissue selection have improved detection. Clinical improvement, radiological response, and patient-reported outcomes are typically used to assess treatment response in clinical studies of patients with PIK3CA-related disorders, but objective assessment of treatment response is difficult using imaging (due to the heterogeneous nature of these disorders, superimposed upon patient growth and development). Despite their limitations, patient-reported outcome tools may be best suited to gauge patient improvement. New therapeutic options are needed to provide an alternative or supplement to standard approaches such as surgery and sclerotherapy. Currently, there are no systemic agents that have regulatory approval for these disorders, but the mTOR inhibitor sirolimus has been used for several years in clinical trials and off label to address symptoms. There are also other agents under investigation for PIK3CA-related disorders that act as inhibitors to target different components of the PI3K signaling pathway including AKT (miransertib) and PI3K alpha (alpelisib).

CONCLUSION

Management of patients with PIK3CA-related disorders requires a multidisciplinary approach. Further results from ongoing clinical studies of agents targeting the PI3K pathway are highly anticipated.

Clinical and genetic evaluation of six children with diffuse capillary malformation and undergrowth

BACKGROUND

Diffuse capillary malformation with overgrowth (DCMO) has been well described. However, capillary malformation with undergrowth (CMU) has been less reported in the literature.

OBJECTIVES

We sought to describe the clinical features and determine associated somatic mutations in patients with CMU.

METHODS

We searched our multidisciplinary vascular anomalies clinic database for patients with CMU. Girth and length limb measurements were performed. In case of discrepancies in length, long leg radiograph studies were obtained. Whole-exome sequencing of blood and involved tissue DNA was carried out.

RESULTS

We included six patients with CM and soft-tissue and bone undergrowth. CMs were patchy, reticulated, segmental, poorly demarcated, pink-red stains affecting the lower limb (five patients) or the whole hemibody (one patient). In five patients, the stain was diffuse, affecting more than one anatomic region. Prominent superficial veins were observed in three patients. Five patients presented with lower limb girth discrepancy; in three of them, there was also lower limb length discrepancy. In the remaining patient, only lower limb length discrepancy was found. Whole-exome sequencing from DNA tissue/blood detected previously described pathogenic somatic mutations on DDR2 (c.314G > A; p.Arg105His), GRHL2 (c.791A > G; p.Glu264Gly), and PIK3CA (c.2740G > A; p.Gly914Arg) genes.

CONCLUSION

We propose the term "diffuse capillary malformation with undergrowth" for extensive reticular CMs associated with proportionate undergrowth. All our patients had a favorable outcome, and no genotype-phenotype association was found.

Constitutively active PIK3CA mutations are expressed by lymphatic and vascular endothelial cells in capillary lymphatic venous malformation

Capillary lymphatic venous malformations (CLVM) are complex vascular anomalies characterized by aberrant and enlarged lymphatic and blood vessels. CLVM appear during fetal development and enlarge after birth, causing life-long complications such as coagulopathy, pulmonary embolism, chronic pain, and disfigurement. Treatment includes surgical debulking, amputation, and recurrent sclerotherapy. Somatic, mosaic mutations in the 110-kD catalytic α-subunit of phosphoinositide-3-kinase (PIK3CA) gene have been previously identified in affected tissues from CLVM patients; however, the cell population harboring the mutation is still unknown. In this study, we hypothesized that endothelial cells (EC) carry the PIK3CA mutations and play a major role in the cellular origin of CLVM. We isolated EC from the lesions of seven patients with CLVM and identified PIK3CA hotspot mutations. The CLVM EC exhibited constitutive phosphorylation of the PI3K effector AKT as well as hyperproliferation and increased resistance to cell death compared to normal EC. Inhibitors of PIK3CA (BYL719) and AKT (ARQ092) attenuated the proliferation of CLVM EC in a dose-dependent manner. A xenograft model of CLVM was developed by injecting patient-derived EC into the flanks of immunocompromised mice. CLVM EC formed lesions with enlarged lymphatic and vascular channels, recapitulating the patient histology. EC subpopulations were further obtained by both immunomagnetic separation into lymphatic EC (LEC) and vascular EC (VEC) and generation of clonal populations. By sequencing these subpopulations, we determined that both LEC and VEC from the same patient express the PIK3CA mutation, exhibit increased AKT activation and can form lymphatic or vascular lesions in mouse.