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A young man with acute paraparesis

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Q1: Describe the changes in the electrocardiogram

The electrocardiogram shows small P waves, broad QRS complexes, and peaked T waves, all of which are consistent with hyperkalaemia. Other electrocardiographic features of hyperkalaemia include prolongation of the PR interval, complete heart block, and atrial asystole. Ventricular fibrillation and standstill may occur with severe hyperkalaemia.

Q2: How would you explain the neurological symptoms and signs?

The acute paraparesis is due to hyperkalaemic paralysis. The patient was treated with intravenous calcium gluconate, sodium bicarbonate, and dextrose and insulin infusion. He made a quick symptomatic recovery within one hour after starting treatment. Hyperkalaemic paralysis which may mimic the picture of acute Guillain-Barré syndrome has been previously described.1Hereditary hyperkalaemic paralysis is a separate clinical entity. Causes of secondary hyperkalaemic paralysis is shown in box 1.

Box 1: Causes of hyperkalaemic paralysis

  • Renal failure.

  • Adrenal insufficiency.

  • Rhabdomyolysis.

  • Administration of potassium salts in intravenous infusions.

  • Aldosterone antagonist (spiranolactone).

Q3: What is the final diagnosis and how would you confirm it?

All the biochemical abnormalities are secondary to chronic autoimmune primary adrenal insufficiency (Addison's disease). The short Synacthen (tetracosactrin) stimulation test, is the most commonly used test for the diagnosis of primary adrenal insufficiency. Adrenal function is considered to be normal if the basal or postcorticotrophin (Synacthen) plasma cortisol is at least 500 nmol/l or preferably, at least 550 nmol/l.2 Basal plasma adrenocorticotrophic hormone concentration is usually raised in primary adrenal insufficiency. This patient showed a flat cortisol response after administration of Synacthen (cortisol concentration 107, 105, and 122 nmol/l at 0, 30, and 60 mins respectively). His antiadrenal cortex antibodies were strongly positive. He was treated with intravenous fluids, hydrocortisone, and fludrocortisone. He was well, and his electrolytes and renal function were normal when seen as an outpatient two weeks later. Causes of primary adrenal insufficiency are shown on box 2.3

Box 2: Causes of primary adrenal insufficiency Gradual onset

  • Autoimmune adrenalitis.

  • Tuberculosis.

  • Adrenomyeloneuropathy.

  • Systemic fungal infections (for example, histoplasmosis).

  • AIDS (opportunistic infections with viruses, fungi, bacteria, or protozoa).

  • Metastatic carcinoma (bronchial, breast, lymphoma).

  • Adrenal infiltration (amyloidosis, sarcoidosis, haemochromatosis).

  • Drugs (ketoconazole, aminoglutethimide, suramin, mitotane, metyrapone).Acute onset

  • Meningococcal and other septicaemias.

  • Warfarin therapy.

  • Coagulation disorders.

  • Antiphospholipid syndrome.

  • Abdominal trauma.

Discussion

The symptoms and signs of chronic primary adrenal insufficiency are non-specific and may vary depending on the chronicity and severity of the adrenal destructive process, and the relative deficiency of glucocorticoids and mineralocorticoids. Patients can present with fatigue, weakness, listlessness, orthostatic hypotension, and weight loss. Gastrointestinal symptoms such as abdominal cramps, nausea, anorexia, vomiting, and diarrhoea are often the presenting features. Hyperpigmentation which affects the skin and mucosal surfaces is the most specific sign of chronic primary adrenal insufficiency, but its absence does not exclude this diagnosis. Addison's disease my be misdiagnosed as anorexia nervosa4 or depression.5

Acute adrenal insufficiency is a life threatening medical emergency which needs immediate medical action. Once the diagnosis is suspected, treatment should be instituted and not delayed for investigations. Plasma samples can be saved for later analysis of the cortisol concentration to confirm the diagnosis. Hypotension, nausea, vomiting, and diarrhoea are prominent features.

In the early stages of chronic adrenal failure, the serum electrolytes are normal, but abnormalities such as hyponatraemia, hyperkalaemia, metabolic acidosis, and renal impairment occur in the later stages of the disease when adrenal destruction is advanced. The hyponatraemia is due to aldosterone deficiency and vasopressin secretion secondary to hypovolaemia. Hyperkalaemia is due to a combination of aldosterone deficiency, acidosis, and renal impairment.

Our patient presented with the acute neuromuscular manifestations of hyperkalaemia (hyperkalaemic paralysis) in the absence of the classical symptoms of chronic adrenal failure, which is a very unusual presentation of Addison's disease.

The predominance of hyperkalaemia in this patient could be partly explained by the absence of vomiting and diarrhoea, which tend to lower the serum potassium level. In addition the severity of metabolic acidosis in the presence of renal impairment is an other contributing factor.

The management of primary adrenal insufficiency consists of glucocorticoid and mineralocorticoid replacement, usually in the form of hydrocortisone and fludrocortisone respectively. Patients should carry a card containing information on current therapy, and they should also wear a bracelet or necklace, such as those issued by Medic Alert.6

Patients must also be advised to double up the dose of hydrocortisone for a few days if they develop a febrile illness, and they should keep ampoules of hydrocortisone in the fridge at home for intramuscular injection, or hydrocortisone suppositories to be used in case of vomiting.7

This case emphasises the importance of excluding metabolic abnormalities in patients presenting with acute neurological symptoms as the response to treatment is usually prompt, and the outcome rewarding.

Final diagnosis

Hyperkalaemic paralysis secondary to chronic autoimmune primary adrenal insufficiency (Addison's disease).

References

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