Institute of Rheumatology and
Institute of Neurologic Sciences, University of Siena, 53100 Siena, Italy
SIR, Focal myositis (FM) is a rare, benign, self-limiting inflammation of the skeletal muscle, of unknown aetiology, initially described by Heffner et al. [1] in 1977. It is typically characterized by a localized, painful swelling of the soft tissues without a systemic involvement, frequently mimicking a sarcoma or thrombophlebitic disease [2]. Infectious aetiology, traumatic or ischaemic events have been suggested to explain the focal nature of the muscle injury in predisposed subjects. The muscle MRI and muscle serum enzyme evaluation are useful tools for diagnosis, which must be confirmed by muscle biopsy examination [24]. We describe one case of a young man with recurrent episodes of bilateral localized FM of the gastrocnemius muscle after a BCG vaccination.
A healthy 22-yr-old man, 3 weeks after a BCG vaccination, developed a sudden pronounced exertional weakness, pain and swelling of the calves with referred increased serum level of CK and erythrocyte sedimentation rate (ESR). The patient was treated with non-steroidal anti-inflammatory drugs and methylprednisolone (8 mg/day). Recovery was complete within a month and the patient stopped drug therapy. One year later, he experienced a further episode of acute calf pain. The EMG showed myopathic changes in the gastrocnemius muscle, bilaterally. Laboratory investigation showed a polyclonal hyper--globulinaemia, increased CK serum level (350 IU/l; normal value 20170) and circulating immunocomplexes, and ESR (27 mm/h). The patient was treated with methylprednisolone (4 mg/day) with a progressive clinical amelioration in a few weeks. The dosage of the drug was tapered and stopped within 1 yr. At the time, laboratory tests were normal.
At 27 yr of age, the patient was admitted to our hospital for walking difficulty, bilateral calf swelling and pain. He denied a history of external trauma and had not had any constitutional symptoms such as fever, malaise or rashes. There was no personal or familial history of connective tissue disorders. Clinical examination showed a tender enlarging mass of the postero-lateral region of the calves, more pronounced on the left side. The subcutaneous tissue did not appear to be involved in the lesion; no regional lymph node enlargement was found. Neurological examination showed difficulty in walking on tip-toe. Laboratory investigation showed an increased level of: CK (2813 IU/l; normal value 20170); aldolase (20 U/l; normal value 1.010); SGOT (52 U/l; normal value 540); SGPT (70 U/l; normal value 540). The ESR was increased (26 mm/h). The Tyne test was strongly positive. The following tests were negative or normal: electrophoresis and renal function, rheumatoid factor, antinuclear, anti-Scl 70, anti-SSA, anti-SSB, anti-Rnp, anti-Jo-1, anti-DNAn and anti-Sm antibodies. Serology for trichinosis, echinococcosys, cysticercosis, toxoplasmosis, Lyme borreliosis, hepatitis and common viral infections were all negative. The chest radiograph was normal. Electromyographic examination only showed myopathic changes with slight denervation in the gastrocnemius muscle, bilaterally. Muscle MRI in the upper and lower limbs showed a focal lesion, with an increased signal on T2 weighted images, confined to the gastrocnemii (Fig. 1). A biopsy of the right lateral gemellus muscle was performed. Histological examination revealed a severe variation in fibre size with clusters of hypotrophic degenerating fibres and some hypertrophied fibres. Six to eight percent of nuclear centralization, some pale necrotic fibres, often undergoing phagocytosis, and several endomysial inflammatory cells, sometimes forming slight perivascular infiltrates, were observed. In addition, there was a slight increase in the endomysial connective tissue (Figs 2 and 3
). Using a NADH-TR stain, some fibres showed areas devoid of activity. A combined treatment with methylprednisolone (8 mg/day) and methotrexate (10 mg/week i.m.) was started, followed by a complete regression of the mass lesion and normalization of inflammation indexes and CK level, within a few months. Two years later, clinical and laboratory data were normal. A further MRI examination showed residual gastrocnemius lesions and the EMG showed myopathic changes. At that time, drug therapy was stopped, and the clinical and serological remission persisted 6 months later.
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In our patient the clinical and histological features, the muscle MRI and the EMG were consistent with the diagnosis of FM. The clinical course usually presents a high rate of spontaneous regression, but focal recurrence in other muscles or a progression to polymyositis have been reported [2, 3, 58]. Such evolution can be suggested by the early increase in serum level of the muscle enzymes as well as the acute phase reactants [28]. In the present case, the bio-humoral abnormalities were associated with a particular recurrent form, always confined to the gastrocnemii. Although the majority of previously reported cases were carefully screened for an infectious cause, the aetiology of FM remains unknown. A study using the polymerase chain reaction failed to find any viral agents [9]. Recently, a case of FM caused by Campylobacter infection has been reported [10], and a possible infectious trigger such as Borrelia burgdorferi has also been described [11]. The BCG vaccination has been suggested as a possible trigger for dermatomyositis [12, 13], but not for FM. In the reported cases [12, 13], muscle symptoms began some weeks after vaccination. In the present case, there may also be a significant temporal relationship between the vaccination and the onset of symptoms. Therefore, our work could support the hypothesis that the BCG vaccination is a possible trigger for FM.
Notes
Correspondence to: S. Manganelli.
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