Infantile myositis presenting in the neonatal period.

Infantile myositis, observed in the neonatal period, is rare and may be confused with congenital muscular dystrophy. The patient presented here showed evidence of a myopathy with in utero onset with intrauterine growth retardation and decreased fetal movements. A muscle biopsy demonstrated characteristic perifascicular atrophy and inflammatory infiltrates. Initial magnetic resonance (MR) examination revealed high signal intensity in several proximal muscle groups. With subsequent corticosteroid treatment, the patient's symptoms, clinical course and MR findings have gradually improved. The diagnosis of infantile myositis should be established as early as possible, since proper treatment can lead to resolution of clinical symptomatology and MR findings.