Brown tumours in association with ulcerative colitis: An unusual case

Clinical History

A 23-year-old male patient presented with abdominal pain, nausea, vomiting, rectal bleeding and weight loss. A series of investigations were undertaken including sigmoidoscopy with biopsy, CT & MRI of the small bowel which all showed active colitis. Multifocal lytic lesions in ilium bilaterally were picked up on CT incidentally.

Imaging Findings

CT examination showed active inflammation in sigmoid and descending colon in the form of wall thickening, an imaging hallmark of ulcerative colitis (UC) [5]. Bilateral sacroiliitis was noted along with an unexpected finding of discrete lytic lesions with a fluid density in both iliac bones.

MRI study of the bowel revealed similar findings and confirmed the cystic nature of the osseous lytic lesions.

Radiographically brown tumours are discrete low attenuating cystic lesions [5] with irregular outline on CT & fluid signal on MRI [1]. These can occur frequently in the pelvis, ribs, and clavicles [1].

Brown tumours may simulate giant cell tumour (GCT), giant cell granuloma (GCG) and metastatic carcinoma [1], knowledge of certain key imaging features can however aid in differentiation. On imaging, GCT lesions are usually epiphyseal & eccentric with pseudotrabeculations, GCG lesions are trabecular with sharp margins and metastatic lesions exhibit surrounding invasion [1].

Discussion

Brown tumours are non-neoplastic lesions, seen as a musculoskeletal manifestation of hyperparathyroidism. They occur more commonly in primary hyperparathyroidism than in secondary hyperparathyroidism [4]. Primary hyperparathyroidism is characterised by a spontaneous abnormal secretion of parathyroid hormone (PTH) and is diagnosed clinically by the presence of hypercalcaemia with increased PTH levels [2]. Gastrointestinal manifestations mostly include vague abdominal complaints and disorders of the stomach and pancreas [3], and do not include involvement of the bowel.

This case had clinical symptoms suggestive of ulcerative colitis (UC), which was confirmed on sigmoidoscopy. However, the clinical diagnosis of primary hyperparathyroidism was not present at the time of radiological imaging. Patient was advised to undergo CT abdomen to delineate the complete extent of large bowel involvement.

The presented case is one of its kind, because in this case brown tumours were seen in a patient diagnosed with UC initially and hyperparathyroidism was subsequently confirmed.

To investigate further, patient’s serum calcium and PTH levels were checked. Results showed hypercalcaemia and increased levels of PTH, consistent with primary hyperparathyroidism in the background of UC. Patient did not have any bone complaints. The hypercalcaemia is asymptomatic in more than 90% of patients with primary hyperparathyroidism [3].

On our literature search, we found no article describing an observation of brown tumours co-existing with UC. Although there are reports of co-existing hyperparathyroidism and ulcerative colitis, most had parathyroid adenoma [6-9] and none had brown tumours.

The initial report of hyperparathyroidism in a patient of ulcerative colitis was documented by Grek & Senior in 1961 [8]. It is postulated that as the calcium levels are reduced in longstanding UC, possibly long term steroid usage can cause an increase in quantities of PTH, which can result in either hypoparathyroidism or hyperparathyroidism (adenoma formation). However, definite pathophysiology still remains unclear.

UC and hyperparathyroidism can co-exist in a same individual and this is being increasingly reported [6-9]. Hence, a clear look out for any additional findings on imaging should be attempted. This case showed lytic lesions in iliac bones in addition to UC findings, & prior knowledge of the coexistence of UC & primary hyperparathyroidism instigated us to investigate further. Early detection & treatment can prevent a cascade of parathyroid crisis.

Differential Diagnosis List

Final Diagnosis

Brown tumours secondary to primary hyperparathyroidism on a background of ulcerative colitis

URL:	https://eurorad.org/case/15281
DOI:	10.1594/EURORAD/CASE.15281
ISSN:	1563-4086