Pediatric macrophagic myofasciitis associated with motor delay

Macrophagic myofasciitis (MMF) is a rare inflammatory myopathy characterized by accumulation of perifascicular macrophages without muscle fiber necrosis. Few sporadic pediatric cases have been described, and MMF is recognized as a possible reaction to intramuscular injections of aluminum-containing vaccines. The association of MMF and motor delay is unclear in the pediatric population. We report the clinical evaluation and follow-up of 4 young children with MMF and review of 4 cases previously reported of sporadic, pediatric MMF to better determine the possible association of sporadic MMF in children presenting with motor delay.

Described our 4 case reports in which we observed children presenting for evaluation of motor delay with unrevealing clinical and laboratory evaluations for common causes of motor delay and histopathological evaluations consistent with macrophagic myofasciitis. Muscle data was obtained by quadriceps muscle biopsy.

Clinical presentations were similar in all children and were characterized by motor delay, hypotonia, and failure to thrive with an unrevealing evaluation for central nervous system disease, congenital, and mitochondrial myopathies.

Our cases and those previously reported in the literature demonstrate MMF should be considered in the evaluation of children with failure to thrive, hypotonia, and muscle weakness, as clinical outcome appears to be favorable.