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Phaeochromocytoma

What is phaeochromocytoma?

Basically a tumour that originates from chromaffin cells of the adrenal medulla. Chromaffin calls are also called phaeochrome bodies due to their dark colour (phaeo=dark, chromo=colour) when stained with chromium salts, hence the long winded name of chromaffin cell tumours.

These tumours commonly arise from the adrenal medulla as that's where chromaffin cells are found, however sometimes extra-adrenal chromaffin cells (found outside of the adrenal gland that fail to regress after birth) can lead to extra-adrenal phaeochromocytomas (aka paragangliomas).

The job of chromaffin cells is to produce catecholamines (fight-or-flight hormones), so having a tumour of chromaffin cells will lead to a huge increase in catecholamines, which as you've guessed will lead to a clinical presentation exemplary of an exaggerated fight-or-flight/sympathetic response.

What causes phaeochromocytoma?

It can happen sporadically (90%!) or in certain familial syndromes (10%)

Familial causes of phaeochromocytoma (autosomal dominant)

  • Type 1 neurofibromatosis
  • Multiple endocrine neoplasia (MEN) syndrome
  • von Hippel-Lindau (VHL) syndrome

(A quick visual aid I made to remember the causes: 1 brainy man riding a hippo :)

The indivdual causes of the above conditions are pretty boring, but the main take-home stuff is:

  • Type 1 neurofibromatosis: Mutation to Neurofibromin tumour suppressor gene
  • MEN syndrome: Mutation to overexpress RET-proto-oncogene
  • VHL syndrome: Mutation to VHL tumour suppressor gene

    How does the patient present?

    As mentioned before, the patient will have an over-excited sympathetic response, which can lead to a plethora of clinical features.

    Symptoms tend to occur intermittently (most likely due to the intermittent release of catecholaimes from the chromaffin cell tumour).

    The main episodic hyperadrenergic symptoms are:

    1. Pressure: Hypertension!, due to arterial vasoconstriction to give elevated BP.
    2. Pain: Abdominal pain and Headaches, due to the increased sympathetic drive
    3. Perspiration
    4. Palpitation
    5. Pallor: Due to the arterial vasoconstriction

    (Don't confuse with the 6P's of acute ischaemia!)

    Phaeochromocytomas are a very rare (<0.1%) cause of hypertension; and so failure to exclude phaeochromocytoma can lead to a hypertensive crisis!

        How do you confirm for phaeochromocytoma?

        • Blood: Raised catecholamine and metanephrines (catecholamine metabolites)
        • Urine: 3 x 24hr urinary collection to check for raised catecholamines and their metabolities
        • CT/MRI scan: Adrenal or extra-adrenal masses
        • Clonidine suppression test: Clonidine is an α2-agonist. The α2-receptor (found in brain) is activated with raised catecholamine levels, and negatively feedbacks to decrease catecholamine release from chromaffin cells. In a normal person, clonidine adminstration will decrease catecholamine levels, however in phaeochromocytoma, the tumour acts independently of the α2-receptor, and so is not suppressed by clonidine.

           (Cl looks like α and clonIdIne has two "i"s, so α2 agonist :) 

        How is phaeochromocytoma treated?

        • Surgical resection of tumour (definitive treatment)
        • Phenoxybenzamine: a non-selective irreversible α-blocker that antagonises the effects of the phaeochromocytoma. Given two weeks prior to surgery.

        (phenOXybenzamine, An ox is really heavy; so hard to move it out of the α-receptor :)

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