Dermatomyosite et pneumopathie interstitielle rapidement évolutive associées aux auto-anticorps anti-MDA-5 : une présentation clinique atypique

Abstract

A new antibody known as anti-MDA-5 has recently been identified in association with a specific phenotype of dermatomyositis (DM), in which muscular involvement is minimal or absent, but where there is a particularly high risk of onset of aggressive interstitial lung disease. Below, we report a case associated with the presence of anti-MDA-5 antibodies complicated by aggressive interstitial lung disease ; the cutaneous phenotype of this patient is novel due to the constitution of diffuse ichthyosis and of profuse subcutaneous calcinosis. A 35-year-old man was hospitalised for a skin rash associated with arthralgia, dry cough, asthenia and weight-loss of 8 kg in 5 months. The dermatological examination revealed purple erythema of the upper eyelids and cheeks, diffuse acquired ichthyosis of the trunk and limbs, and striated erythema on the proximal and distal metacarpal and interphalangeal joints of the fingers. A diagnosis of DM was suspected in patients treated with prednisolone, 1.5 mg/kg/d. Immunological tests identified the presence of anti-MDA-5 antibodies. One month later, the cutaneous signs continued to progress and were marked by the development of painful ulcers on the back of the fingers, as well as dyspnoea accompanying the slightest effort. Chest images showed constituted pulmonary fibrosis lesions. At the same time, within several months, diffuse, pseudo-tumoural calcifications developed in the subcutaneous tissue of the trunk and limbs. The patient was treated successively with intravenous gammaglobulins, cyclophosphamide, mycophenolate mofetil, azathioprine and rituximab in combination with oral corticosteroids, but with no improvement in respiratory function or in the skin lesions. Because of the decline in the patient's respiratory status, a lung graft was envisaged but subsequently abandoned because of the patient's excessively precarious state of health. Anti-MDA-5 antibody appears to constitute a specific immunological marker for a special dermatological phenotype of adult DM, significantly associated with the presence of: 1) keratotic papules in the skin folds of the palms and fingers ; 2) cutaneous ulcers along the periungueal edges, Gottron's papules on the back of the hands and on the extensor surface of the elbows and knees ; 3) pain and ulceration in the oral mucosa, diffuse alopecia, and appearance of "mechanic's hands" and Gottron's sign on the elbows and knees. To our knowledge, the presence of extensive ichthyosis and profuse subcutaneous calcinosis has not been previously reported in this particular form of DM. The risk of aggressive interstitial lung disease is particularly high and worsens the prognosis, since 40% of patients with anti-MDA-5 die, usually within the first year. Herein, we describe a patient presenting amyopathic DM complicated by aggressive interstitial lung disease associated with the presence of anti-MDA-5 antibodies, but with a hitherto unreported cutaneous phenotype combining diffuse ichthyosis and profuse subcutaneous calcinosis.