clinic visit by the isolation of characteristic calcium pyrophos-

Letters to the Editor
9 Hemminki K, Fo¨rsti A, Lorenzo Bermejo J. Etiologic impact of known cancer
susceptibility genes. Mut Res Rev 2008;658:42–54.
10 Alamanos Y, Drosos AA. Epidemiology of adult rheumatoid arthritis. Autoimmun Rev
2005;4:130–6.
Rheumatology 2008;47:551–552
doi:10.1093/rheumatology/ken016
Advance Access publication 12 February 2008
Pseudoneuropathic CPPD arthropathy: magnesium matters
A
B
clinic visit by the isolation of characteristic calcium pyrophosphate dihydrate crystals from left knee synovial fluid.
His thiazide diuretic was stopped and he was reviewed by a
nephrologist who prescribed magnesium replacement therapy.
His serum magnesium level has remained between 0.63 and
0.68 g/l since.
He has undergone a successful left ankle arthrodesis that has
improved his pain and functional status with a plan for a rightsided arthrodesis in the future.
There are few reports in the literature of pseudoneuropathic
arthropathy caused by calcium pyrophosphate crystal deposition.
It was first reported by McCarty and Haskin in 1963 [1]. There
is no distinctive pattern of pseudoneuropathic arthropathy, but
it does have a distribution that is atypical for OA. It affects both
weight-bearing joints and non-weight-bearing joints as there
have been a number of cases of destructive arthropathy of the
temporomandibular joint reported [2, 3]. The natural history of
this form of CPPD arthropathy has not been well documented;
however, it does lead to pronounced joint destruction over a
relatively short period of time. It is unclear whether pseudoneuropathic arthropathy has a distinct pathological process or whether
it represents end-stage pseudogout-like CPPD.
Hypomagnesaemia has been strongly associated with CPPD
crystal deposition [4].
Low-serum magnesium can be due to a variety of disorders
including Gitelman’s syndrome [5], short bowel syndrome [6] and
familial forms of renal magnesium wasting [7] all of which have
been reported as causes of chondrocalcinosis and CPPD arthropathy. The use of thiazide diuretics can also predispose to the
development of chondrocalcinosis [4]. The impairment of the
activity of pyrophosphatases that occurs in the relative absence of
magnesium is the proposed pathological mechanism by which
magnesium deficiency produces calcium pyrophosphate crystal
production [8]. The clinical presentation of CPPD associated with
hypomagnesaemia is generally severe and of early onset as was the
case here [8]. There is an opinion that magnesium levels need
not be checked in patients presenting after the age of 50 as any
disorder of magnesium homeostasis is likely to have become
clinically obvious before this [9]. This case illustrates the need to
determine magnesium levels in patients with CPPD at all ages,
particularly in the presence of thiazide diuretic use.
The distinction between a true neuropathic joint and pseudoneuropathic joint is an important one. The presence of denervation obviously has a large bearing on the likelihood of successful
surgery. Surgeons are naturally slow to operate on joints that have
been denervated due to the risks of poor healing and infection [10]
that exist in such cases. There is also evidence that the longterm outcome from arthrodesis procedures in patients with
persistent neuropathy is poor. Those with even severe destructive
arthropathy who have preserved neurological function do well
post-operatively [10]. As this case illustrates, the absence of
neuropathy should be established as it opens up the possibility
of operative interventions in patients with severe destructive
arthropathy.
Rheumatology key message
Hypomagnesaemia as a cause of CPPD should be considered in
the context of thiazide diuretic use.
Disclosure statement: The authors have declared no conflicts
of interest.
B. R. WHELAN, F. O’SHEA, G. MCCARTHY
FIG. 1. (A) Posterior clinical image of the ankle joints (right ankle post-arthrodesis).
Note the gross deformity of the left ankle. (B) The radiograph is an anteroposterior
view of left ankle showing severe joint destruction and subluxation.
Department of Rheumatology, Mater Hospital, Dublin, Ireland
Accepted 8 January 2008
The Author 2008. Published by Oxford University Press on behalf of the British Society for Rheumatology. All rights reserved. For Permissions, please email: [email protected]
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SIR, Pseudoneuropathic calcium pyrophosphate deposition
(CPPD) arthropathy is a rare form of arthropathy caused by
deposition of calcium pyrophosphate crystals within the joint
space.
We wish to present a case of severe destructive pseudoneuropathic CPPD of the ankles due to hypomagnesaemia, treated
successfully with ankle arthrodesis. A 56-yr-old man with a 2-yr
history of bilateral ankle joint pain and swelling of sudden onset
was referred to rheumatology services from orthopaedics because
of the suspicion of an underlying inflammatory arthropathy. He
had previously had a right total knee replacement aged 48 for
what was diagnosed as early degenerative OA. His only other
significant medical history was of hypertension for which he had
received a thiazide diuretic (bendroflumethiazide 5 mg once daily)
for the previous 4 yrs and quinapril 10 mg o.d. for the previous
2 yrs. He had no family history of early onset OA or other
inflammatory arthropathy.
Initial assessment by rheumatology revealed him to have a
markedly antalgic gait. He had a 158 fixed flexion deformity of his
left knee with a genu varus but with no clinically appreciable joint
effusion. His right knee, which had previously been replaced, was
of normal alignment and moved well. He had marked deformity
of his ankles with his feet held in eversion and in prominence of his
medial malleoli (Fig. 1A).
Investigations revealed normal full blood count, renal profile,
serum calcium, free T4 and TSH, fasting glucose and glycosylated
haemoglobin. Alkaline phosphatase was normal at 101 mmol/l.
A glucose tolerance test was also normal. Initial ESR was 4, ferritin
was on the upper limit of normal at 336 g/l, but transferrin
levels were normal. Genetic screening for haemochromatosis
revealed no characteristic polymorphisms. He was found to be
hypomagnesaemic at 0.48 g/l (normal range 0.64–0.87 g/l).
Plain radiographs (Fig. 1B) showed a severe destructive
arthropathy of both ankles.
Radiographs of the left knee revealed evidence of articular
chondrocalcinosis. Formal sensory nerve conduction studies and
EMG of the lower limbs were within normal limits.
He was diagnosed with pseudoneuropathic calcium pyrophosphate deposition arthropathy that was confirmed at a subsequent
551
552
Letters to the Editor
Correspondence to: B. R. Whelan, Department of Rheumatology, Mater Hospital, Eccles St, Dublin 7, Ireland.
E-mail: [email protected]
Rheumatology 2008;47:552–553
doi:10.1093/rheumatology/kem357
Advance Access publication 15 February 2008
Successful treatment of resistant scleroderma-associated
interstitial lung disease with rituximab
SIR, We report the case of a 57-yr-old patient who presented with
an 18-month history of scleroderma. This had been diagnosed
previously in another institution where she was treated with i.v.
infusion therapy of methylprednisolone at 10 mg/kg and cyclophosphamide 15 mg/kg. She failed to respond to the initial six
courses of therapy, and had a further five infusions. Unrelated to
her medical condition, she moved to our region where she
presented to the respiratory service in February 2004 with
worsening dyspnoea. She reported hand pain, stiffness and
swelling and restriction of shoulder movements, with worsening
Raynaud’s phenomenon, and was also referred to rheumatology.
When she attended the rheumatology clinic in August 2004, she
was wheelchair bound due to dyspnoea and had an intermittent
cough, but not productive of sputum. There was no chest pain or
haemoptysis. The patient was in respiratory distress and had
difficulty talking, with a resting respiratory rate of 40/min and
oxygen saturation of 92% on room air. She was not centrally
cyanosed and had bibasal coarse crackles, but her jugular venous
FIG. 1. HRCT showing (A) pre-retreatment with rituximab and (B) post-treatment with the second course of rituximab, demonstrating a reduction of the ground glass
appearance and resolution of the air bronchograms in midzones (arrows). At this stage, the lung bases demonstrated irreversible fibrotic changes with honeycombing.
The Author 2008. Published by Oxford University Press on behalf of the British Society for Rheumatology. All rights reserved. For Permissions, please email: [email protected]
Downloaded from http://rheumatology.oxfordjournals.org/ by guest on September 9, 2014
1 McCarty D, Haskin M. The roentgenologic aspects of pseudogout (articular
chondrocalcinosis). An analysis of 20 cases. Am J Roentgenol 1963;90:1248–57.
2 Osano H, Matsumoto K, Kusama M. Calcium pyrophosphate dihydrate
arthropathy with condylar destruction of the temporomandibular joint. J Oral Sci
2003;45:223–6.
3 Onodera K, Ichinohasama R, Saito M, Ooya K. A case of the calcium pyrophosphate
dihydrate (CPPD) deposition disease without condylar destruction of the temporomandibular joint. Pathol Int 1997;47:622–6.
4 Jones AC, Chuck AJ, Arie EA, Green DJ, Dohrerty M. Diseases associated with
calcium pyrophosphate deposition disease. Semin Arthritis Rheum 1992;22:188–202.
5 Punzi L, Calo L, Schiavon F, Pianon M, Rosada M, Todesco S. Chondrocalcinosis
is a feature of Gitelman’s variant of Bartter’s syndrome. A new look at the
hypomagnesemia associated with calcium pyrophosphate dihydrate crystal deposition disease. Rev Rhum Engl Ed 1998;65:571–4.
6 Richette P, Ayoub G, Bardin T, Bouvet S, Orcel P, Badran AM. Hypomagnesemia
and chondrocalcinosis in short bowel syndrome. J Rheumatol 2005;32:2434–6.
7 Milazzo SC, Ahern MJ, Cleland LG, Henderson DR. Calcium pyrophosphate
dihydrate deposition disease and familial hypomagnesemia. J Rheumatol
1981;8:767–71.
8 Rosenthal A. Crystal induced arthropathies. In: Wortmann RL, Schumacher HR,
Becker MA, Ryan LM, eds. New York: Taylor and Francis, 2006; 104 (chapter 3).
9 Becker MA. Clinical manifestations and diagnosis of calcium pyrophosphate crystal
deposition disease. UptoDate, v. 15.3, 2007. (http://patients.uptodate.com/topic.
asp?file¼crystald/3066, date last accessed 15 February 2007).
10 Wetmore RS, Drennan JC. Long-term results of triple arthrodesis in CharcotMarie-Tooth disease. J Bone Joint Surg Am 1989;71:417–22.
pulse was not elevated, heart sounds were normal, no murmurs
were detectable and she had no dependent oedema. She had puffy
scleroderma of the hands with marked synovitis and bilateral
shoulder capsulitis. There was extensive telangiectasia on her
hands and face, and facial skin tightening with beaking of the
nose. She also had symptoms of heartburn and was taking
omeprazole 20 mg daily.
The chest X-ray demonstrated signs of pulmonary fibrosis at
both bases. Her blood count was normal, ESR and CRP were
30 mm/h and 28 mg/l (normal <10 mg/l), respectively; rheumatoid
factor was negative but ANA was strongly positive at a titre of
1 : 2560 with a homogeneous pattern; extractable nuclear antigens
including Scl-70 were negative. High-resolution CT (HRCT)
performed before her rheumatology review showed basal honeycombing and a ground glass appearance compatible with
scleroderma-related interstitial lung disease (ILD). Her pulmonary function test showed a forced vital capacity (FVC) of 1.84 l
(100% predicted), forced expiratory volume in 1 s (FEV1) to FVC
ratio was 88.01, and the diffusing capacity of the lung for carbon
monoxide (DLCO) was 1.1 mmol/min/kPa (62.7% predicted).
In September 2004, she was treated with rituximab 1000 mg
2 weeks apart with 100 mg of methylprednisolone premedication
prior to the infusions. She improved within 3 weeks and managed
to walk up to 500 m. Her FVC improved to 2.01 l (109.5%).
Her arthropathy resolved completely. She started prednisolone
5 mg daily and cyclosporin 50 mg twice daily. In late 2005,
there was deterioration in her symptoms, and in February 2006 a
repeat HRCT showed ground glass changes compatible with midzone pneumonitis (Fig. 1A). Her FVC had reduced to 1.69 l
(93.5% predicted) and her DLCO was 0.62 mmol/min/kPa (34.3%
predicted). She was developing cor pulmonale; an echocardiogram
performed confirmed an enlarged right ventricle with impaired
function with right ventricular systolic pressure of 132 mmHg and
raised pulmonary artery pressures. In view of the success of the
original infusion she was retreated with the same rituximab
regimen. Following therapy she resumed her walking distance of
500 m. Her repeat FVC and DLCO improved to 2.02 l (113%
predicted) and 0.84 mmol/min/kPa (48% predicted), respectively,
and the repeat HRCT (Fig. 1B) showed an improvement. Air
bronchograms evident on HRCT in the upper and mid-zones were
less conspicuous following therapy.
Peripheral blood cytometric evaluation using a sensitive assay
after the second treatment was determined. Following therapy the
B-cells were 0.0001 109/l (normal levels 0.060.66 109/l) and
pre-plasma cells 0.0002 109/1. The good clinical response noted
in the face of peripheral blood B-cell lymphopenia likely reflects
the presence of pathogenic B cells in the lymphoid and possibly
pulmonary tissues.
The monoclonal antibody rituximab is directed against the
CD20 antigen that is expressed on B lymphocytes. Rituximab has
been used to treat non-Hodgkin’s lymphoma where it has good