Hemifacial hyperplasia or hemifacial hypertrophy is a rare developmental anomaly characterized by asymmetric growth of hard and soft tissues of the face 1.
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Epidemiology
These asymmetries are often noted at birth and are usually accentuated with increasing age, especially around puberty 2.
The disorder occurs more commonly in females (ratio 3:2) 1.
Pathology
Various theories have been proposed. These include vascular lymphatic, hormonal, and asymmetric development of the neural fold, with hyperplasia of neural crest cells 3.
It is a condition that appears to affect the derivatives of the first pharyngeal arch, though the middle ear structures seem spared 3.
Hemifacial hypertrophy (HFH) is classified as 4:
- true hemifacial hypertrophy (THFH): unilateral viscerocranial enlargement
- partial hemifacial hypertrophy (PHFH): not all structures are enlarged
Radiographic features
Unilateral enlargement of all the viscerocranial structures bounded by the frontal bone, excluding the eye; inferiorly by the inferior border of the mandible and the midline; and laterally by the ear.
Enlargement and deformity of all tissue of the face, including teeth and their related tissues in the jaw, are the key findings in the diagnosis of hemifacial hypertrophy 5.
Differential diagnosis
Isolated hemifacial hyperplasia is a diagnosis of exclusion, because there are other conditions that can cause facial asymmetry including 1:
- Proteus syndrome
- Beckwith-Wiedemann syndrome
- neurofibromatosis type 1
- vascular malformations such as Klippel-Trenaunay syndrome and lymphaticovenous malformations
History and etymology
Hemifacial hyperplasia was first mentioned by Meckel in 1822 4.
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