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Polymyositis and pregnancy: report of a case with three pregnancies
  1. University Department of Neurology, Medical School of Patras University, Greece
  1. Professor Thodoros Papapetropoulos, Department of Neurology, Medical School of Patras University, Regional University Hospital of Patras, PO Box 1045, 26 500 Rion, Greece.

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Reports of polymyositis and dermatomyositis during pregnacy are uncommon and the available data referring to the possibility of recurrence as well as to the risks for the pregnant woman and the fetus are limited.

The association of polymyositis-dermatomyositis and pregnancy is very rare, and this has been attributed to the low percentage (14%) of cases in which the disease begins during the reproductive period of a woman’s life1; it is also probable that family planning policy after the clinical manifestation of the disease lowers the association of polymyositis-dermatomyositis and pregnancy.

A 35 year old woman was admitted to our neurological department (May 1992) after 16 weeks of pregnancy, with a six week history of fatigue, myalgia, and proximal muscle weakness of all four limbs which was progressively worsening.

At the age of 17 years she had been investigated (blood biochemistry, EMG, and muscle biopsy) at the University Department of Neurology in Athens where the diagnosis of polymyositis (first episode) was established. After three years of steroid treatment she recovered completely and five years later, when already married, she had a normal male baby without any relapse of her illness during gestation or postpartum. On admission to our department neurological examination showed bilateral weakness of the sternocleidomastoid and proximal muscle weakness of all four limbs (grade 3-4 of MRC scale). The rest of the cranial nerves were normal, there was no dermal rash or Reynaud’s phenomenon and her general physical examination was normal. Laboratory investigations showed an erythrocyte sedimentation rare of 25 mm/hour, creatine kinase 3760 IU/l (normal value<190 IU/l), lactate dehydrogenase 415 (normal 80-260 IU/l),serum glutamic oxalacetic transaminase 115 IU/l (normal 5-35 IU/l), serum glutamic pyruvic transaminase 103 IU/l (normal 5-35 IU/l); antinuclear antibodies were negative and thyroid function tests were normal. Electromyography of deltoid, biceps, and quadriceps muscles showed myopathic changes (short duration, low amplitude, and polyphasic motor unit potentials) and a few neuropathical findings (spontaneous fibrillation potentials and positive sharp waves). Conduction velocity studies of the upper and lower limbs were normal. Muscle biopsy of the left deltoid (paraffin and cryostat sections) showed muscle fibre necrosis, phagocytosis, regeneration, diameter variation, interstitial fibrosis, mild infiltrates of chronic inflammatory cells which were mainly perivascular, and occasional perifascicular muscle fibre atrophy. The diagnosis of polymyositis was confirmed according to the criteria of Swash and Schwartz and the patient was started on steroid treatment (62.5 mg prednisone/day). A few days later, her muscle weakness deteriorated rapidly. At this stage both her husband and the patient became very anxious about the probable complications and the decision was taken for an emergency termination of pregnancy by caesarian section at the end of 16 weeks. Three weeks after the termination of pregnancy she was discharged home with considerable improvement. The steroid treatment was continued on a schedule of reducing doses (every other day) for the next two years when it was discontinued due to her complete recovery. Thirty months after the last pregnancy and without any clinical or laboratory evidence of relapse she had her second normal baby (female) by caesarian section. She has remained in remission.

Polymyositis-dermatomyositis is rarely a life threatening disease for pregnant women and there is only one case report of maternal death which was attributed to severe exacerbation of the disease.2 Women in remission at the time of conception tend to have a more favourable outcome and exacerbations can usually be controlled with costicosteroids.2

In active polymyositis-dermatomyositis associated with pregnancy healthy infants resulted only in 30% of cases, premature babies in 30%, and fetal death or abortion in 40%, whereas during inactive or improved polymyositis-dermatomyositis the figures were 57%, 21.5%, and 21.5% of cases respectively.3 Most authors who have reviewed the literature on the association of polymyositis-dermatomyositis and pregnancy advocate, when this is clinically required, steroid treatment.4 The criteria for initiation and discontinuation of steroids as well as steroid dosage should be identical during pregnancy and in the non-pregnant state.3 The risk to the fetus of steroid administration seems very low, as placental enzymes inactivating prednisolone decrease the fetal steroid blood concentration to 10% of the mother’s blood concentrations.4 Finally for patients on steroids at the time of delivery, additional hydrocortisone is recommended to prevent acute adrenal insufficiency.5

In our present case it is not clear whether the improvement was due to the pregnancy termination or was a slightly delayed response to treatment. If it was the termination which had the positive effect on the patient’s condition this might be of interest from an immunological point of view.

In conclusion the present case report shows that the occurrence of polymyositis during one pregnancy does not necessarily dictate its recurrence with subsequent pregnancies. Women should be discouraged to become pregnant during the active phase of the disease and if pregnancy does occur during remission a close follow up is necessary by frequent creatine kinase estimations.