Plexiform lesion

This section is from a 15 year old obese girl with primary pulmonary hypertension. Plexiform lesions are glomus-like structures that emerge at right angles from a muscular artery and bulge into a plexus of channels whose walls consist of fibrous tissue covered by endothelial cells.

This section from the same patient shows a dilation lesion evolving from a plexiform lesion.  The patient had no history of ingestion anti-obesity medication.

Pulmonary hypertension can be secondary to various cardiac and infectious diseases and, when severe, plexiform lesions can be present. Primary pulmonary hypertension is a rare disease characterized by markedly elevated pulmonary artery pressure of undetermined cause and plexiform lesions. The typical patient is a woman between the ages of 20 and 40 years. She usually presents with dyspnea and chest pain. The disease carries a poor prognosis with death usually ensuing within 2-5 years. About 10% of cases are familial with autosomal dominance. Mutations in the bone morphogenic protein receptor type 2 have been noted. This protein normally downregulates endothelial proliferative response after injury. Before making a diagnosis of primary pulmonary hypertension, one must exclude cardiac causes, HIV positivity, CREST syndrome, drugs such as anorexigens or cocaine or amphetamines, and recurrent pulmonary emboli. Treatment with calcium channel blockers and vasodilators has been less than satisfactory but newer therapies are being developed. Lung transplantation can be considered.

Plexiform lesions were seen in an hydropic stillborn with pulmonary hypertension secondary to premature closure of the ductus arteriosus. Trichrome stain.

Premature closure of the ductus arteriosus results in pulmonary hypertension. The fetal lungs which are receiving no inhaled oxygen offer much vascular resistance to blood flow. Normally in fetal life most of the blood entering the pulmonary trunk from the right ventricle traverses the ductus to enter the descending aorta with only a small amount going into the lungs. With closure of the ductus all of the right ventricular output must enter the lungs resulting in pulmonary hypertension because of the high vascular resistance. Pulmonary hypertension is reflected in right heart pressures and ultimately right heart failure, i.e. fetal hydrops. A case such as this suggest that no more than several months of pulmonary hypertension can lead to plexiform lesions.