Tumor of chromaffin tissue (neuroectodermal origin),
most commonly affecting the adrenal medulla (90% of patients), but may
occur in any tissue derived embryologically from the neuroectoderm,
including any sympathetic ganglia, the GI tract, bladder, and thorax.
Total incidence: 2 to 8 cases per 1 million people of
which 10% occur in children. It is the cause of 1 to 2% of systemic
hypertension cases in the pediatric population. Compared to adults, children
are more likely to present tumors that are bilateral, multiple, or
extraadrenal in origin. Familial cases are also more common in children and
adolescents. It is more frequent in boys than in girls.
Autosomal dominant. Mutation of RET
protooncogene that is located on chromosome 10. Pheochromocytoma can be
associated with Neurofibromatosis type I, von Hippel-Lindau Disease,
Multiple Endocrine Neoplasia type IIa (Sipple syndrome), Tuberous Sclerosis
(Bourneville disease), Sturge-Weber Disease, or Carney triad (gastric
leiomyosarcoma, pulmonary chondroma, and extraadrenal pheochromocytoma).
Ninety percent of tumors are benign; multiple
sites occur in approximately 35% of children and in 8% of adults.
Epinephrine can only arise from the adrenal medulla, norepinephrine can
arise from any sympathetic tissue. Elevated catecholamines cause an increase
supraventricular rhythm, hypertension, increased cardiac contractility, and
rate. Hyperglycemia may result from alpha-2 antagonism of insulin secretion.
The catecholamines are metabolized by monoamine oxidase and
catechol-O-methyltransferase, 5% of norepinephrine being excreted
unchanged; urinary levels reflect plasma levels.
History and examination, especially finding of
paroxysmal or sustained hypertension at a young age. Demonstration of
elevated urine catecholamine levels.
Symptoms include sweating, palpitations,
headache, pallor, vomiting, weight loss, polyuria, polydipsia, and chest
pain, which may be cardiac in origin. Examination reveals hypertension,
which may be sustained or paroxysmal tachycardia, hypertensive retinopathy,
and possibly signs of ventricular failure caused by dilated cardiomyopathy.
The ECG may reveal dysrhythmia. In childhood, other catecholamine-secreting
tumors, such as neuroblastoma, ganglioneuroblastoma, and ganglioneuroma,
should be considered in the differential diagnosis. The tumor may be defined
by ultrasonography, CT scan, or MRI scan. Laboratory investigations may
reveal a raised hematocrit. Urinary vanillylmandelic acid (VMA) and
metanephrines are elevated, as are plasma catecholamine levels. Extraadrenal
sites of tumor should be excluded by 131metaiodobenzylguanidine (MIBG)
uptake scan. In children, norepinephrine is usually the predominant
catecholamine. In case of metastatic malignant tumor, therapeutic doses of
131I-MIBG are administered.
History: Inquire for symptoms of
dysrhythmia or ventricular dysfunction. Catecholamine-induced cardiomyopathy is present
in approximately 58% of patients. Cardiovascular assessment: ECG, echocardiography. Start alpha
blockade. Competitive alpha-antagonists (e.g., phentolamine, prazosin) have
been used but do not give the same stability as noncompetitive blockade
(phenoxybenzamine). Beta blockade may be started after alpha blockade to
control dysrhythmias. The minimum duration for alpha blockade is 36 hours,
although the optimal period is not defined. End points used for adequate
blockade have included a 5% drop in hematocrit or the maximum dose of ...