Fibromuscular hyperplasia of the pulmonary artery in sudden infant and perinatal death

INTRODUCTION : The purpose of this study was to describe cases presenting with fibromuscular hyperplasia of the pulmonary arteries that could belong to the group of sudden infant death syndrome (SIDS) and sudden unexpected perinatal death "gray zone" or borderline cases. METHODS: In a total of 12 cases, eight females and four males, ranging in age from 39 gestational weeks to 93 postnatal days, dying suddenly and unexpectedly, a fibromuscular hyperplasia of the pulmonary artery was detected. Postmortem examinations were requested with a clinical SIDS or sudden unexpected perinatal death. A complete autopsy was performed, including close examination of the brainstem and cardiac conduction system. RESULTS: Histological examination showed the presence of various degrees of fibromuscular hyperplasia with fibrosis of the right (six cases), left (five cases) or both (one case) pulmonary arteries. CONCLUSIONS: In our cases, fibromuscular hyperplasia of the pulmonary artery alone might or might not have accounted for the sudden deaths, if it had not been for the concomitant presence of hypoplasia of the arcuate nucleus in the brainstem and/or cardiac conduction system abnormalities. Therefore, they were classified as SIDS/sudden unexpected perinatal death gray zone or borderline cases. Necropsy studies of sudden infant and perinatal death should always include an accurate gross and histological examination of the pulmonary arteries, as well as of the brainstem and cardiac conduction system.