Abstract
Introduction
Calcium pyrophosphate disease (CPPD) can present both acutely with hot, swollen and painful joints, often with an underlying trigger, or with chronic forms of arthritis resulting in slower joint destruction. A rare and often misdiagnosed presentation is crowned dens syndrome (CDS). Classically, these patients present with neck pain, possible fever and raised inflammatory markers. Peripheral joints may also flare with CPPD simultaneously and there may be a precipitating event. We describe two cases of CDS recently encountered at Poole Hospital in Dorset.
Case description
Case 1: A 74-year-old male presented with acute onset foot pain, neck pain, fever, elevated CRP (192 mg/l) and normal urate (226micromol/l). He had hypomagnesaemia (0.22mmol/l) and hypocalcaemia (1.99mmol/l). He reported three months of diarrhoea and took omeprazole 20 mg twice daily. He had a negative infection screen with normal vitamin D and parathyroid hormone levels. CT C-spine showed soft tissue calcification around the odontoid peg and down to C2. However, initially the radiology reporting did not clearly identify CDS as a possible differential; an input from the rheumatologist was required for re-reporting of the scan with CDS in mind. He was successfully treated with a weaning course of oral prednisolone starting at 15 mg daily, weaning by 5 mg weekly and switching his omeprazole to famotidine.
Case 2: An 85-year-old lady presented to the community team with 10 months of intractable cervical pain, headaches and difficulty sleeping. An MRI of the C-spine showed erosive and hypertrophic changes at the C1/2 articulation; a CT showed calcification of the ligaments posterior to the odontoid PEG. Following a spinal MDT discussion, a more chronic form of CDS was thought to be the most likely diagnosis. She was treated with non-steroidal anti-inflammatory drugs (lack of response), colchicine (intolerance) and targeted injection.
Discussion
We describe two patients with CDS - one presenting acutely and the other with a more chronic history. This highlights the challenge in diagnosing CPPD as the clinical picture can be highly variable. A high index of suspicion is required, especially in elderly patients presenting with neck pain; in such situations, a CT scan of the cervical spine allows rapid exclusion of fractures, identification degenerative disease and diagnosis of CDS. Another interesting observation was that one of our patients had hypocalcaemia and hypomagnesaemia, both of which could potentially be involved in the pathogenesis of CPPD/CDS. Although hyperparathyroidism and resulting hypercalcaemia can cause CPPD in its more chronic form, hypocalcaemia may result in the mobilisation of calcium pyrophosphate crystals, triggering an inflammatory response and acute CPPD. Magnesium is a cofactor for alkaline phosphatase which is involved in breakdown of pyrophosphate; a deficiency in magnesium can result in pyrophosphate build up, which can trigger pseudogout attacks. Furthermore, magnesium is involved in parathyroid hormone and thereby calcium regulation; a significant deficiency in magnesium can cause a hypocalcaemia which can precipitate acute pseudogout as well. Common causes for low magnesium include the use of proton pump inhibitors and chronic diarrhoea, which can be addressed to reduce the risk of future attacks of CPPD. This case highlights the importance of investigating for an underlying cause for CDS. We suggest that all patients with CDS and acute CPPD have a bone profile and magnesium performed, both of which are easily available; identifying and addressing these electrolyte abnormalities and their causes can help treat the CDS and prevent future attacks. From our cases, a weaning course of prednisolone over weeks appears to be successful in treating CDS. Shorter courses may risk a relapse and treatment-resistant cases may benefit from the addition of colchicine.
Key learning points
Our cases highlight four key learning points:
• Elderly patients presenting with acute neck pain without any history of trauma and raised inflammatory markers, a high index of suspicion for CDS and an early investigation with CT of the cervical spine allows rapid diagnosis of this condition and exclusion of other differentials.
• CDS can often have an underlying trigger precipitating the CPPD. Two important causes we highlight here are low calcium and low magnesium, both of which can play a role in the pathogenesis of acute CDS presentations.
• Despite having had reported CT scans on the cervical spine, CRS was not initially reported by the reporting radiologist suggesting under-recognition of this condition.
• We suggest the use of a weaning regime of prednisolone initially as a successful treatment option with lower chance of relapse. Colchicine and targeted injections can be alternatives.