A 71-year-old woman with no past history of interest who, after 6 months of dermatitis on the face, trunk and extremities, was diagnosed in July 2013 by skin biopsy as having DM with skin involvement, without reporting muscle weakness. Muscle enzymes CK and aldolase were normal. ANA positive (1:320) and Mi-1:Mi-2 positive (1:320) with anti-P155/140 negative. Tumour markers and a complete CT scan do not demonstrate the presence of neoplasia. Acute phase reactants are elevated, CRP 44.2 mg/L [0 - 5] and ESR 73 mm/h [0 - 19]. He was treated with prednisone at a dose of 30 mg/24 h in various descending doses for 4 months. During this period, she progressively began to experience myalgia and muscle weakness that forced her to be bedridden, with fever, dysphagia and weight loss of 10 kg.
In December 2013, she was admitted on suspicion of DM with the appearance of myopathy. An electromyogram (EMG), magnetic resonance imaging (MRI) and muscle biopsy confirmed inflammatory myopathy in the proximal muscles of the extremities. An oesophagogram confirmed significant oesophageal motor impairment and delayed gastric emptying. She was diagnosed with MD with muscular and digestive involvement, as well as skin involvement. The pulmonary study and echocardiogram were normal.
For the first 8 days, corticosteroid therapy prior to admission was maintained. Cinitapride was prescribed as a prokinetic. On the ninth day, after confirming the myopathy, azathioprine 50 mg/24h was started. Intravenous (IV) methylprednisolone pulses were added for 3 days, followed by prednisone 30 mg/24h for 2 weeks (then a tapering schedule). On the seventh day after starting azathioprine, GOT/AST 160 U/L [2 - 35] and GPT/ALT 313 U/L [2 - 35] were detected, the previous levels being normal. It was decided to discontinue azathioprine due to hepatotoxicity and the pharmacist reported the suspected adverse reaction to the Pharmacovigilance Centre. Mycophenolate 500 mg/24h is started, for which the patient signs an informed consent form and the documentation for the use of drugs in special situations is completed. The dose was increased to 1 g/12h.

After 6 weeks of treatment, she reported improvement in muscle strength, increased physical activity, significant reduction in dysphagia and dermatitis, with normalisation of acute phase reactants and transaminases, continuing with normal CK and aldolase. It was decided to discontinue cinitapride and continue with a tapering prednisone regimen. After 9 weeks of therapy, she reported hair loss and paresthesia in the lower limbs, which are described as frequent adverse reactions in the mycophenolate data sheet. At week 12 the prednisone dose was lowered from 10 mg to 7.5 mg /24h. At the 14-week follow-up, the patient described a 10-cm pruritic erythematous plaque similar to those seen at the onset of the disease. The only change observed in the laboratory tests was an increase in CRP to 29.2 mg/L. The alopecia stabilised, the paraesthesia disappeared and it was decided to return to 10 mg of prednisone every 24 hours. At week 16, CRP normalised to 4.1 mg/L and the skin condition disappeared, returning to a dose of 7.5 mg /24h of prednisone. At week 20, CRP remained in range and there were no signs of dermatitis, and prednisone 7.5 mg /24h plus 1 g /12h of mycophenolate therapy was considered safe and effective in controlling the disease in this patient.