Adult-onset inflammatory myopathy: North Canterbury experience 1989-2001.
OBJECTIVE
To perform a clinical audit of all patients diagnosed with inflammatory myopathy in the North Canterbury region.


METHODS
A retrospective case note audit of patients with a discharge diagnosis of inflammatory myopathy from June 1989 to June 2001 was performed. The audit was based at Christchurch Hospital, New Zealand, which services a population of 430,000.


RESULTS
Of 77 case notes reviewed, 44 patients were identified who were considered to fulfil clinical criteria for inflammatory myopathy. There was a female preponderance (80% female, 20% male). Diagnostic categories in descending order of frequency included: dermatomyositis (41%), polymyositis (39%), inclusion body myositis (IBM) (14%) and overlap syndromes (6%). Malignancy-associated myositis occurred in 20% overall (dermatomyositis 11%, polymyositis 9%). Delays in diagnosis and late age at presentation (average 72 years) were seen in the IBM group. Proximal limb weakness was common, but not universal at presentation (80%). A muscle biopsy was performed in all patients and electromyography in 82%. All were treated with high dose prednisone (0.5-1 mg/kg) of whom 29% were maintained on prednisone alone. Immunosuppressives/immunomodulators used included: azathioprine (58%), methotrexate (31%), intravenous immunoglobulin (13%), chlorambucil (13%), and cyclophosphamide (9%). Thirteen patients (42%) required more than one agent, with three trialling five agents. There were 59 relapses in 20 patients (45%), with mean time to first relapse of 7.8 months. At audit completion, 33% had deceased with malignancy and respiratory failure the main causes.


CONCLUSIONS
Inflammatory myopathy is a challenging condition in both diagnosis and management. Our audit has shown delays in the diagnosis of IBM, a relatively high incidence of malignancy and a notable risk of relapse and mortality.
Lynn
S J
SJ
Department of Rheumatology, Christchurch Hospital, Christchurch, New Zealand.
Sawyers
S M
SM
Moller
P W
PW
O'Donnell
J L
JL
Chapman
P T
PT
D000368:Aged; D001706:Biopsy; D003951:Diagnostic Errors; D004359:Drug Therapy, Combination; D004576:Electromyography; D005260:Female; D005938:Glucocorticoids / Q000627:therapeutic use; D006801:Humans; D007166:Immunosuppressive Agents / Q000627:therapeutic use; D015994:Incidence; D008297:Male; D008485:Medical Audit; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000473:pathology; D009220:Myositis / Q000175:diagnosis* / Q000188:drug therapy / Q000453:epidemiology; D009520:New Zealand / Q000453:epidemiology; D010351:Patient Discharge; D011241:Prednisone / Q000627:therapeutic use; D012189:Retrospective Studies; D012720:Severity of Illness Index; D016896:Treatment Outcome
D005938:Glucocorticoids; D007166:Immunosuppressive Agents; D011241:Prednisone