Purpose or Case Report: Infantile myofibromatosis (IM) is a rare congenital disease of early childhood. Approximately 50% of cases are diagnosed prenatally, and 90% are diagnosed prior to 2 years of age. Solitary IM, multicentric IM without visceral involvement, and generalized IM with cutaneous and visceral involvement have been described, with generalized IM carrying a poor prognosis and high mortality rate. The following reported case demonstrates an unusually high disease burden.
The patient was a monochorionic diamniotic twin fetus found to have a cystic and solid left facial mass on routine prenatal anatomy scan. Initial differential included congenital hemangioma, as well as lymphatic malformation and teratoma. Multiple prenatal ultrasounds and fetal MRI were obtained between gestational age 22w0d and delivery. At 32w2d, a new large paraspinal mass extending from the thoracic spine to the proximal right lower extremity was noted. During retrospective review, mild soft tissue thickening was noted in this region on fetal MRI. At this point, a vascular malformation was favored, with a differential of congenital rhabdomyosarcoma less likely. Ultrasound surveillance for the remainder of the pregnancy showed enlargement of the paraspinal mass with extension into the right retroperitoneal space.
The patient was delivered at 35w0d gestation via cesarean-section. On physical examination, she was found to have multiple masses involving the face, and the paraspinal, buttock, and bilateral lower extremity soft tissues. While atrophic papules were present, there were no overlying skin changes as would be expected with vascular malformations. Given the firmness of the masses and atrophic papules, the diagnosis of infantile myofibromatosis was suspected.
Whole-body MRI with contrast was obtained, demonstrating extensive heterogeneously enhancing soft tissue masses involving the left check, lower back extending into the retroperitoneal space, bilateral gluteal muscle and lower extremities.
The patient’s clinical status declined, and given the poor prognosis, was transitioned to comfort care and expired at age 2 months. Post-mortem autopsy confirmed the diagnosis of generalized infantile myofibromatosis with innumerable myofibromas of the right atrium, ventricles, intercostal muscle, diaphragm, thyroid, lungs, pancreas, adrenal glands, vertebrae, and paraspinal muscles.
The surviving twin is currently 2 years of age and is screened with whole-body MRI annually without evidence of disease.
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