E023 Intimomedial mucoid degeneration. A rare vascular disease mimicking giant cell arteritis presentation
Authors: Black Sarah , Wray Maria , Stewart Helen , Durkan Ellen , Serafimov Viktor , Davey Philip , Smith Lisa 
Published: April 2024

Abstract

Background/Aims
The accuracy of giant cell arteritis (GCA) diagnosis has greatly improved in recent years with increasing use of fast track clinics and vascular ultrasound. The “halo” sign is recognised as confirmation of a positive test and is considered virtually pathognomonic of GCA in the setting of a correlating clinical presentation. There are caveats to this and “false halos” have been reported associated with arterial thickening seen in other conditions including atherosclerosis and lymphoma. In this case a focal area of arterial wall thickening mimicking a halo on ultrasound was due to a rare vascular condition called intimomedial mucoid degeneration.

Methods
A 63 year old female presented via the direct assessment unit to the fast track GCA service. She reported an 8 week history of a tender right forehead lump and a 3 week history of associated new headache with marked tenderness at the site of the lump. The headache was severe and had become persistent. Mild shoulder stiffness was present. No jaw claudication. Blurring while wearing glasses noted but no definite visual change. CRP 2mg/L, ESR at usual baseline of 30mm/hr. Other indices normal. On examination: No shoulder restriction. No visual field deficit. Palpable pulsatile area of artery right side of forehead that was exquisitely tender with less marked tenderness of the artery adjacent to this. No symptoms on left side. GCA probability score (GCAPS) 10 indicating intermediate probability of GCA.

Results
Temporal artery ultrasound performed using GE Logiq e and 10-22mHz probe. Left side imaged entirely normally. Right side symptomatic area imaged as a focal asymmetric thickened area of frontal branch artery measuring 1.5mm maximally in compression. The frontal branch artery imaged normally proximal and distal to this as did the right common superficial and parietal branches. Features were unusual however she was commenced on prednisolone 40mg daily pending further investigations. Eye assessment detected no ischaemic concerns. She returned for reassessment after 4 days. There was some symptomatic improvement however the tender lump persisted. A second opinion on the ultrasound was sought from the interventional radiologist, who felt the focal area may be a lymph node, with thickened artery adjacent. Surgical exploration and temporal artery biopsy was subsequently performed.

Conclusion
Histology showed there was actually mucoid change with eccentric thickening of the artery with aneurysmal change in keeping with the rare diagnosis of intimomedial mucoid degeneration. This is a very rare condition which causes predisposition to arterial aneurysm formation, and typically presents with acute pain of the artery involved. This lady had developed an aneurysm which was excised at the time of the biopsy, relieving her symptoms. This case is a reminder to pursue additional investigations and tissue diagnosis in the setting of unusual clinical and imaging findings.

Disclosure
S. Black: None. M. Wray: None. H. Stewart: None. E. Durkan: None. V. Serafimov: None. P. Davey: None. L. Smith: None.