The exact etiology and pathogenesis of IH is unknown but is an area of vigorous investigation that has been accelerated by the development of an IH mouse model.
IH is neoplasm of benign endothelial-like cells that possess the markers GLUT-1, Lewis Y antigen, Fc®RII, and merosin and stem cells, and pericytes.
The etiology is unknown, but popular theories include a placental embolus, a somatic mutation in a gene-mediatingendothelial cell proliferation, or origination from an endothelial progenitor cell (CD34+, CD133+).
They present in the first few weeks of life with a precursor lesion that can appear as a bluish bruise-like patch, telangiectasias with a rim of pallor, or a red flat stain.
IHs have a characteristic natural history consisting of three phases:
The rapid proliferation phase: 3 weeks until 6 to 7 months of age; IHs experience rapid volumetric growth and appear red, firm and have a rubbery texture (Fig. 1.13).
The plateau (or late proliferative) phase: variable length, usually 7 to 12 months of age; IHs have a slower rate of growth and color changes to a dull red to gray and begins to break apart and lesions feel soft or spongy.
The involution phase: usually starts at 1 year of age and is a gradual process that can last for years; the color continues to fade, some lesions involute completely while others leave fibrofatty residua (Fig. 1.14).
IH can be superficial (Fig. 1.15), deep or mixed (superficial and deep) (Fig. 1.16).
Lesions with a deep component will grow for about month longer than superficial IH.
More recent studies show that most IH growth is complete by 5 months of age and that involution ends at median age 3 years.
Ulceration is the most common complication and is heralded by a gray-white color during the proliferative phase (Fig. 1.17).
IHs in certain locations and of certain morphologies are at higher risk for development of complications and/or associated systemic involvement (see Table 1.2, for a list of high-risk IHs and intervention required). For example, IHs in the perineum are at highest risk for early ulceration, IHs in the central face can lead to permanent cosmetic disfigurement, and large segmental IHs (configuration corresponding to a recognizable and/or significant portion of a developmental segment) on the face should prompt workup for PHACES syndrome.
Early recognition of high-risk IH will allow for more timely intervention.
Topical Treatments
Propranolol
Dosing
Systemic Corticosteroids Treatments for Ulceration
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