LONG CASE RESOURCE

Approach to Addison's Disease

Primary Adrenal Insufficiency • MRCP (UK) PACES

A structured PACES approach to the patient presenting with progressive tiredness due to primary adrenal insufficiency. Learn focused history taking, examination, differential diagnosis, investigations, management and examiner-focused discussion.

10 min read Presenting Complaint High Yield

At a Glance

Presentation Progressive fatigue with weight loss and postural dizziness

Most Likely Diagnosis Primary Adrenal Insufficiency (Addison's Disease)

Classic Examination Finding Generalised hyperpigmentation including buccal mucosa and palmar creases

Must Not Miss Addisonian Crisis

Diagnostic Test Short Synacthen Test

Treatment Hydrocortisone ± Fludrocortisone Replacement

Overview

Addison's disease (primary adrenal insufficiency) is a classic high-yield PACES topic. Patients usually present with progressive fatigue, weight loss, postural dizziness, gastrointestinal symptoms and characteristic hyperpigmentation. Candidates should demonstrate a structured history, recognise important examination findings, identify associated autoimmune disorders and explain lifelong steroid replacement with sick-day rules.

Structured History

Progressive fatigue and lethargy
Unintentional weight loss
Postural dizziness or syncope
Anorexia, nausea, vomiting or abdominal pain
Salt craving
Generalised weakness and reduced exercise tolerance
Skin darkening noticed by patient or relatives
Previous autoimmune disease (thyroid disease, T1DM, vitiligo)
History of tuberculosis, HIV or adrenal surgery
Current or previous corticosteroid therapy

Examination

General appearance and weight loss
Measure lying and standing blood pressure
Generalised hyperpigmentation
Buccal mucosal pigmentation
Pigmentation of palmar creases, scars and pressure areas
Look for vitiligo
Signs of dehydration
Examine for associated autoimmune disease

Differential Diagnosis

Secondary adrenal insufficiency Hypothyroidism Chronic infection Malignancy Depression Haemochromatosis Anorexia nervosa Chronic liver disease

Investigations

Morning serum cortisol
Plasma ACTH level
Short Synacthen Test (gold standard)
Urea, electrolytes and glucose
FBC (look for eosinophilia)
21-hydroxylase antibodies
Thyroid function tests
CT adrenal glands if indicated

Diagnosis

Primary Adrenal Insufficiency (Addison's Disease)

The diagnosis is suggested by progressive fatigue, weight loss, postural hypotension and characteristic hyperpigmentation. It is confirmed by an inadequate cortisol response to the Short Synacthen Test together with an elevated ACTH level.

Management

Hormone Replacement Hydrocortisone ± Fludrocortisone

Treat Underlying Cause Autoimmune disease, tuberculosis or adrenal pathology

Patient Education Sick-day rules, MedicAlert identification and emergency hydrocortisone

Explaining to the Patient

"Addison's disease occurs when the adrenal glands are unable to produce enough cortisol. This explains your tiredness, weight loss and dizziness. Treatment involves lifelong steroid replacement. During illness or surgery, you will need extra steroid doses to prevent an adrenal crisis, and we will teach you exactly how to adjust your medication."

Examiner's Corner

Common Causes of Primary Adrenal Insufficiency

Autoimmune adrenalitis Tuberculosis Metastatic malignancy Adrenal haemorrhage Fungal infection HIV Adrenoleukodystrophy Bilateral adrenalectomy

Why does hyperpigmentation occur?

Primary adrenal insufficiency causes increased ACTH production. ACTH is derived from POMC, which also produces MSH (Melanocyte Stimulating Hormone). Increased MSH stimulates melanin production leading to pigmentation of the skin, buccal mucosa, palmar creases and scars.

How do Primary and Secondary Adrenal Insufficiency differ?

Primary	Secondary
High ACTH	Low ACTH
Hyperpigmentation	No pigmentation
Hyperkalaemia	Potassium usually normal
Needs Fludrocortisone	Usually not required

Management of Addisonian Crisis

ABC assessment
IV Hydrocortisone 100 mg immediately
Rapid IV 0.9% saline
Treat hypoglycaemia if present
Correct electrolyte abnormalities
Identify and treat the precipitating cause

Pathfinder Pearls

Think Addison's in unexplained fatigue Check lying & standing BP Always inspect the buccal mucosa Palmar crease pigmentation is high yield Remember associated autoimmune disease Synacthen Test confirms diagnosis Teach sick-day rules Know Addisonian Crisis management

Common Pitfalls

Not examining the buccal mucosa.
Failing to measure postural blood pressure.
Missing vitiligo or other autoimmune disorders.
Confusing primary with secondary adrenal insufficiency.
Forgetting fludrocortisone replacement in primary disease.
Not counselling about sick-day rules.
Not recognising an Addisonian Crisis.

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