PHACE(S) Syndrome With Absent Intracranial Internal Carotid Artery and Anomalous Circle of Willis

[Research progresses in the pathogenesis, diagnosis and treatment of infantile hemangioma with PHACE syndrome]

Infant hemangioma, the most common benign tumor in children, is characterized by rapid proliferation, followed by slower spontaneous involution. However, some patients with facial segmental hemangioma are associated with PHACE syndrome. PHACE syndrome is characterized by vascular nerve and vascular cutaneous lesions of multiple systemic systems, often resulting in structural and functional impairments. Recent studies have demonstrated that the possible pathogeneses of PHACE syndrome mainly include hypoxia, abnormality of mesodermal vascular endothelial cells, genetic abnormality, and abnormality of interstitial mesenchymal stem cells. The current medications for hemangioma with PHACE syndrome include beta blockers, glucocorticoids, and mTOR inhibitors. This review article mainly describes the pathogenesis, diagnoses and treatments of PHACE syndrome, in order to provide directions for diagnosis and treatment of this disorder.

Does hypoxia play a role in infantile hemangioma?

Infantile hemangioma (IH), the most common tumor of infancy, is characterized by rapid growth during infancy, followed by spontaneous involution over 5-10 years. Certain clinical observations have led to the suggestion that IH is triggered and maintained by hypoxia. We review the literature on the possible role of hypoxia in the etiology of IH, in particular, (1) the role of hypoxia inducible factor-1α (HIF-1α) and its downstream targets including GLUT-1 and VEGF; (2) the pathophysiological link between IH and retinopathy of prematurity; (3) hypoxic events in the early life including placental insufficiency, pre-eclampsia and low birthweight that have the potential to promote hypoxic stress; and (4) the evidence supporting the development of IH independent of HIF-1α. We also discuss these observations in the context of recent evidence of the crucial role of stem cells and the cytokines niche that governs their proliferation and inevitable differentiation, offering novel insights into the biology of IH. We propose that various triggers may simultaneously up-regulate HIF-1α, which is downstream of the renin-angiotensin system, specifically angiotensin II, which promotes production of HIF-1α. These developments shed light to the understanding of this enigmatic condition.

PHACE syndrome--clinical features, aetiology and management

PHACE syndrome comprises a spectrum of anomalies including posterior fossa malformations, haemangioma, arterial anomalies, cardiac defects and eye anomalies. PHACE should be considered in any patient with a large facial segmental infantile haemangioma (IH), and multidisciplinary management is crucial. Low-dose propranolol is effectively for the treatment of IH associated with PHACE syndrome. Recent evidence suggests IH is comprised of mesoderm-derived haemogenic endothelium.

CONCLUSION

The embryonic developmental anomaly nature of IH provides an insight into the origin of PHACE syndrome.