Online Clinical Case Study (May 2003)

Clinical Cardiology Series
臨床心臟科個案研究

Which of the following statements concerning digoxin is true, please explain?

The content of the Office Cardiology Series is provided by:
Dr. Wong Shou Pang, Alexander
F.R.C.P., F.H.K.A.M.(Med.), F.H.K.C.P., Specialist in Cardiology
Dr. Li Siu Lung, Steven
M.B.,B.S.(H.K.), M.R.C.P.(U.K.), F.H.K.A.M., F.H.K.C.P., F.R.C.P.(Glasg.), Specialist in Cardiology
臨床心臟科個案研究之內容誠蒙王壽鵬醫生及李少隆醫生提供。

Answers

1.

It is principally metabolized in the liver.

False. 70% of the drug is eliminated unchanged through the kidney.
 

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2.

Dialysis is the first line emergency treatment during digoxin overdose.

False. It has a large apparent volume of distribution mostly bound to skeletal muscle receptors and thus is not effectively removed by peritoneal dialysis or hemodialysis.
 

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3.

Digoxin is useful in treating atrial fibrillation.
 

True. It enhances vagal effect over AV node, thus slowing resting heart rate. However, in conditions with high sympathetic tones, it should be used concomitantly with calcium channel blockers or beta-blockers.
 

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4.

Due to its negative chronotropic effect, digoxin should be avoided in patients with congestive heart failure.
 

False. Its inotropic action enhances cardiac output, improves symptoms and hemodynamics. However, it does not reduce mortality.
 

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5.

Digoxin is useful in patients with Wolff-Parkinson-White syndrome and atrial fibrillation.
 

False. It may accelerate antegrade conduction over the accessory pathway and may precipitate ventricular fibrillation.
 

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6.

Digoxin is useful in patients with hypertrophic obstructive cardiomyopathy.
 

False. The inotropic effect may worsen the outflow gradient.
 

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7.

In treating atrial fibrillation, dose of digoxin should be increased if it is used concomitantly with amiodarone.

 

False. Amiodarone, quinidine, propafenone and flecainide would all increase the serum digoxin level due to a decreased clearance.
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Dermatology Series 皮膚科病例研究

A four year old girl presented with itchy skin rash over trunk and limbs since she was few months of age. The rash was itchy and may swell after scratching or bathing. Her family history was unremarkable. Physical examination revealed multiple yellow-tan maculopapular lesions mainly on her trunk. A wheal was formed upon rubbing (See arrow).
The content of the Dermatology Series is provided by:
Dr. Tang Yuk Ming, William and Dr. Chan Loi Yuen
Specialist in Dermatology & Venereology
皮膚科病例研究之內容誠蒙鄧旭明醫生及陳來源醫生提供。

 

Answers

1. What is the clinical diagnosis?

The diagnosis is urticaria pigmentosa (UP). UP is a form of mastocytosis with mast cell proliferation mainly in the skin.
 

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2.

What is the diagnostic clinical sign in this condition?

Darier's sign. It refers to the urtication, erythema and itch after the skin lesion is being rubbed or scratched. Release of histamine and other mediators from mast cells may be provoked by skin friction; extremes of heat or cold; exercise; ingestion of hot beverages, spicy food, ethanol and drugs (such as NSAIDs, opiate analgesics, quinine, iodine-containing X-ray contrast media); and insect's sting.
 

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3. How would you confirm your clinical diagnosis?

The diagnosis of UP can be confirmed by skin biopsy which shows increased mast cells in the dermal papillae, particularly near blood vessels. Mast cells can be more clearly demonstrated by special stains such as toluidine blue and Giemsa.
 

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4. What are the possible complications of this dermatoses?

Mastocytosis can also involve other organs such as gastrointestinal tract, liver, spleen and bone marrow.

Massive release of histamine may cause flushing sensation, abdominal pain, vomiting, diarrhoea, headache, palpitation, tachycardia, hypotension, syncope and even anaphylaxis. Gastric hypersecretion due to elevated plasma histamine may cause gastritis and peptic ulceration. Bone marrow involvement can cause anaemia, bone pain and pathological fracture. Mast cell leukaemia may rarely occur.
 

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5.

What is the treatment?

Patients should avoid precipitating factors. First line treatment is with antihistamines. H2 antagonists may be required in addition to H1 antagonists. Topical corticosteroid under occlusion is also effective. Disodium cromoglycate can inhibit degranulation of mast cells. Photochemotherapy has been shown to be effective. Epinephrine may be needed in case of anaphylaxis as may occur after insect's sting. Half children with UP will have resolution by adulthood.
 

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