Polymyositis associated with overlap syndrome (a case report).
Polymyositis identifies a group of patients in whom the mascular weakness is the principle clinical feature often associated with muscle pain, tenderness and wasting, or other form of connective tissue diseases; the muscle biopsy generally demonstrates areas of muscle fibre necrosis accompanied by interstitial and/ or perivascular cellular infiltrates. The presence of erythamatous skin rash in one third of cases makes the term dermatomyositis (DM) more appropriate. Most authors consider polymyositis and dermatomyositis as variants of same disorders, the Polymyositis-Dermatomyositis complex (PM-DM Complex).,
The rarity of this condition and good therapeutic response to steroids prompted us to report this case and highlight the diagnostic features of this condition.
A seven year old male child was brought with complaints of moderate and continuous fever and facial skin rash for ten days and puffiness of face in mornings followed by edema feet and oliguria for two days. There was a history of passing high coloured urine for a day prior to admission. On examination, the child was febrile and had maculopapular, erythematous, non-pruritic facial rash in a butterfly distribution. His blood pressure was 140/100 mm of Hg.
With a tentative diagnosis of acute glomerulonephritis with hypertension, the child was started on an appropriate treatment. The investigations showed urine with trace albumin but no other abnormalities, leucocyte count of 13,000/mm3 with 75% polymorphs and 25% lymphocytes and ESR of 25 mm at end of 1 hour. His throat swab was bacteriologically negative and ASLO titre was not raised. His BUN, serum creatinine, serum electrolytes, serum proteins, serum complements and cholesterol were within normal limits, whereas creatinine clearance was 45 ml/hr. During his stay in the ward, his urine out-put ranged between 200-400 ml/24 hrs., his edema feet increased, he had persistent fever upto 39°C. In view of these findings, a diagnosis of a collagen disorder of systemic lupus erythomatosus type was entertained. The report of ANA in serum was strongly positive and LE cell testing was negative. The child was given a trial with 2 mg/kg of steroids, and he showed dramatic response in form of disappearance of edema and skin rash with improvement in urine out-put within few days.
On abdominal ultrasound the kidney sizes were normal and no abnormality was detected on intravenous pyelography; kidney biopsy showed a normal histology.
During the course of stay in hospital, after the bed rest was omitted, the child showed marked muscle weakness without any pain or tenderness. Weakness was generalised but was more in lower limbs than upper and more proximal than distal. The child had typical Gower's sign. He was unable to climb stairs or raise his arms above head and had a very poor grip. There was no obvious wasting but he had generalised hypotonia even of neck and back muscles with absent deep tendon reflexes. Retrospectively, interrogation revealed a history of pain and tenderness of right thigh, with limping for ten days prior to admission. In view of these neurological findings, serum CPK was estimated which was raised to 10 µm/ml/hr. Nerve conduction was normal, EMG showed typical myopathic pattern but the muscle biopsy showed a normal histology.
In view of proximal and symmetrical muscle weakness, raised serum CPK, typical myopathic EMG and skin rash, this patient was diagnosed to have Polymyositis-Dematomyositis complex using criteria of Bohan and Peter. As the child presented like acute nephritis, with positive serum ANA, the complete diagnosis of Type V polymyositis associated with overlap syndromes was given, according to the classification suggested by Pearson and Bohan.
The patient was put on steroids (2 mg/kg) and showed a very good response in muscle weakness over weeks, in form of disappearance of Gower's sign, ability to climb up stairs and raise arms above head and improvement in grip with return of deep tendon reflexes. The patient was advised to follow-up for serum CPK and ANA investigations and to taper off steroids very gradually when the above reports were normal.
Myositis associated with overlap syndromes is usually of paroxysmal variety and has been associated with one or another of connective tissue disorders. Pearson and Bohan found an incidence of 21% of this type. The connective tissue disorders especially include progressive systemic sclerosis with typical sclerodermatous skin changes and Raynaud's phenomenon and occasionally systemic lupus erythematosus as in our case and rheumatoid arthritis.
Polymyositis may occur at any age from infancy to late adult life, majority in 40 to 60 years age. The onset may be acute with myoglobinuria, subacute or chronic with muscular, dermatological or articular manifestations. The diagnosis is clinical, confirmed by biochemical studies, EMG and muscle biopsy. Bohan and Peter have recommended that for establishing diagnosis of polymyositis certain criteria must be adopted.
Muscle biopsy is diagnostic if the muscle is carefully selected. In general, a proximal muscle that is partially weakened is the best choice. The EMG may be a useful guide for selecting a muscle for biopsy. The muscle biopsy may be normal in 10-15% of cases,,,, as in our case, where the diagnosis was based on other four criteria.
High dose corticosteroid therapy has proved to be the only form of effective therapy for polymyositis,,,,,, monitored by serum CPK and clinical improvement. In acute disease, the initial recommended dosage of prednisolone is 2 mg/kg/day. Once the enzyme levels return to normal, the dosage should be gradually lowered over a period of 5-6 months to an average maintainance dose of 5-15 mg which is continued indefinitely. If following reduction of dosage, the enzyme levels rise, the dose should be immediately increased by 10-15 mg and reduction programme should be followed more slowly thereafter. Very rarely it is possible to discontinue therapy completely even though complications of steroid therapy may pose a problem.
When there is no response to high dose steroid therapy for 3 to 4 months, patients are regarded as steroid resistant and immunosupressants like cyclophosphamide, methotrexate or azathioprine with low dose steroids, can be tried. Recently probenecid has been used in cases of Type V polymyositis with scleroderma and systemic calcification, with complete reversal of calcification.
Prognosis in an acute case is good when treatment is started early and restoration of near normal strength can be expected. DeVere and Bradley suggested that patients with Type V polymyositis, fared poorly, prognosis depending upon the nature of connective tissue disorder they have. In patients treated with steroids Rose and Walton have reported overall mortality of 30% which falls to 16% after exclusion of patients who had malignant neoplasms.
We are grateful to the Dean, Seth G.S. Medical College and K.E.M. Hospital, Parel, Bombay 400 012 for allowing us to publish this case.