Background Inflammatory myopathy with abundant macrophages (IMAM) is a rare and recently discovered clinical condition, which has been proposed as one of the causes of inflammatory myopathy. IMAM is characterized by the diffuse infiltration of macrophages into muscle and fascia with fiber damage. The underlying mechanism responsible for IMAM remains unknown. Severe forms of IMAM might be associated with macrophage activation syndrome (MAS).
Objectives In this report, a very rare condition, a case of childhood IMAM with MAS is presented.
Methods An 11-year-old girl was suffering from fever, generalized erythematous rush, severe musculoskeletal pain and edema in lower extremities. Physical examination showed fever causing elevated body temperature up to 40° C, generalized maculopapular rash, swelling, pain and limitation of motion in the legs. Heliotrope rash and Gottron's papules were not detected. After admission, laboratory tests revealed the following: white blood cell (WBC) count of 3.3x103/μL, platelet (plt) count of 120 x103/μL, C reactive protein (CRP) level of 10.8 mg/dl, lactate dehydrogenase level of 937 U/l, ALT level of 77 U/l, AST level of 194 U/l, creatine kinase (CK) level of 1021 U/l, fibrinogen level of 1.44 g/L, erythrocyte sedimentation rate of 2 mm/h, ferritin level of 3414 ng/ml and triglyceride level of 447 mg/dl. Bone marrow aspiration was performed for differential diagnosis and revealed hemophagocytosis. Bacterial cultures of blood and bone marrow were negative. EBV, CMV, Parvovirus, hepatitis A, B, and C infections were ruled out according to specific Ig G and M levels. Magnetic resonance imaging of lower extremities revealed thickening of the fascia, fasciitis and myositis.
Results MAS in association with myositis led to the diagnosis of IMAM. The patient was treated with intravenous methylprednisolone (30 mg/kg/day) for three days. On third day of treatment, fever, rash and swelling of legs subsided. At the end of the first week, patient was discharged with prednisolone and did not show a relapse of symptoms thereafter.
Conclusions As far as we know, this is the first reported IMAM case with MAS during childhood. It should be kept in mind that, in the evaluation phase of inflammatory myositis, laboratory findings of MAS should be searched for.
Fujikawa K, Migita K, Shigemitsu Y, Umeda M, Nonaka F, Tamai M, et al. MEFV gene polymorphisms and TNFRSF1A mutation in patients with inflammatory myopathy with abundantmacrophages. Clin Exp Immunol. 2014 Nov;178:224-8.
Hara S, Henmi T, Kawakami A, Fujikawa K, Mukae H, Ishimatsu Y, et al. Clinical, serologic and magnetic resonance imaging of 3 cases of inflammatory myopathy with abundantmacrophages in the Japanese population. Rheumatol Int. 2013 Apr;33:1059-64.
Disclosure of Interest None declared