Teaching Case

A 20-year-old female with swelling and redness on the left side face since birth. She presented with similar findings 3 years back and underwent surgical excision of a part of the lower lip on the left side with limited documentation. The swelling has now recurred (Figures 1a, 1b, 1c).

CT

Increased thickness of left buccal and premaxillary fat (Figures 2a and 2b). Left half of tongue shows fatty infiltration (Figure 2c). Areas of fatty infiltration seen in left parotid gland.

MRI

Ill-defined soft tissue proliferation of the left cheek appearing T1/T2W hyperintense and hypointense on fat-saturated images, suggesting fatty infiltration without abnormal flow voids or enhancement (Figures 3a to 3f).

Asymmetrical enlargement of left half of the tongue with T1/T2W hyperintense signal within suppressing on fat-saturated images suggesting fatty infiltration (Figure 4a).

Fatty infiltration into left masseter, medial pterygoid muscle and parotid gland (Figure 4b).

Mild enlargement of left zygoma, left maxilla and mandible:

• Increased thickness of left ramus of mandible compared to the right (Figure 5a).
• Increased thickness of left condylar process of mandible (Figure 5b).

USG

Increased thickness and echogenicity of subcutaneous tissue of left cheek showing no abnormally increased vascularity ( Figures 6a and 6b).

Background

Congenital infiltrating lipomatosis of the face (CILF), also called facial infiltrating lipomatosis is a rare congenital disorder characterised by infiltration of mature lipocytes in the soft tissues of the facial region [1]. Clinically, it manifests as unilateral facial hypertrophy, capillary blushing with hypertrophy of both soft and hard structures like the tongue and mandible. It may progress with age, gradually causing enlargement of the affected side with resultant facial asymmetry. Pathophysiology is not that clear, but recent studies have shown associations with a somatic mutation in the PIK3CA gene [2]. Some of the features of the condition like facial hypertrophy and capillary blush are evident clinically, other features require imaging with CT and MRI. These imaging features include fatty infiltration in facial soft tissues, unilateral macroglossia with fatty infiltration, infiltration into the parotid gland, hypertrophy of bones and macrodontia [3]. There may be associated neurological abnormalities like hemimegalencephaly of the same side, band heterotopia and hypertrophy of the brainstem and cerebellum [4].

Imaging perspective

This patient presented with swelling of the left cheek and lips since birth, which has progressed gradually with an increase in facial redness. USG, CT and MRI performed on the patient revealed soft tissue proliferation on the left side of the face involving the cheeks and lips with fatty infiltration. Ipsilateral fatty hypertrophy of the tongue with fatty infiltration into the left masseter, medial pterygoid muscles and left parotid gland was also noted. Involvement of bony structures was noted in the form of enlargement of the left zygoma, maxilla and mandible. These features are consistent with congenital infiltrating lipomatosis of the face. Treatment of this condition is surgical resection, which has a high rate of recurrence [5]. This patient had undergone a surgical resection 3 years back, followed by recurrence, consistent with the diagnosis.

Take home message

Congenital infiltrating lipomatosis of the face is a rare condition, but awareness of this condition is necessary for the proper evaluation of patients who present with facial asymmetry. Imaging with CT and MRI plays an important role in the diagnosis of this condition, ruling out other possibilities and also helping in proper surgical planning.

Written, informed patient consent for publication has been obtained.