What is the diagnosis?

Long QT Syndrome. Long QT syndrome is a prototypic cardiac channelopathy characterized by profound genetic and phenotypic heterogeneity. The incidence may be as high as 1 in 3,000 persons and it is a common cause of autopsy negative sudden unexplained death. The typical presentation is a child or young adult with unexplained fainting that is precipitated by physical exertion or auditory startle.

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If the initial ECG was normal, what further test may reveal the underlying diagnosis?

Epinephrine QT stress test. Researchers from Mayo clinic have reported their experience in using epinephrine infusion to unmask concealed Long QT syndrome, especially LQT 1 syndrome. In this test, epinephrine was infused in a 25 minutes protocol from dose of 0.025 to 0.3 ug/kg/min. The change of QT interval was then measured. A sensitivity of 92.5% and a specificity of 86% were reported for LQT1 status.

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About 500 LQTS-associated mutations have been reported in 5 genes encoding essential channel subunits, including KCNQ1 (LQT1), KCNH2 (LQT2), SCN5A (LQT3), KCNE1 (LQT5), and KCNE2 (LQT6).

What are the treatment modalities available?

Beta-blocker therapy is the mainstay of treatment. It prevents cardiac events in about 70% of patients. Patients who have experienced cardiac arrest, especially if already on beta-blocker therapy or who continue to have syncope might benefit from device therapy with an implantable cardioverter-defibrillator (ICD).

What is the clinical diagnosis?

The clinical diagnosis is allergic contact dermatitis to hair dye. The most likely chemical present in a hair dye that would cause allergic contact dermatitis is para-phenylenediamine (PPD). PPD hair dye usually comes in a 2-bottles preparation, one with PPD and the other with oxidizer. It is the partially oxidized state that may cause allergy.

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How would you confirm the diagnosis?

A patch test should be performed to confirm the clinical diagnosis and identify the contact allergen. (Please refer to Dermatology series Dec 2005 issue for detail.)

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What is the treatment?

The hair and scalp should be washed thoroughly to remove excessive PPD. Diluted hydrogen peroxide or potassium permanganate solution help to oxidize the remaining PPD. Treatment with topical corticosteroid and antihistamine should be used. Systemic corticosteroid may be required in severe cases.

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How would you advise the patient against recurrence of the rash?

He should avoid further contact with PPD by checking against the ingredient composition of hair dye products. Semi-permanent hair dyes, metallic hair dyes or vegetable rinse hair dyes may be considered instead of using permanent hair dye.

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Are there any possible associations?

PPD may also be found in dark coloured cosmetics, black rubber, printing ink, photo developer and lithography plate and occasionally in textile or fur dyes. Patients allergic to PPD may also be sensitive to para-aminobenzoic acid (used in sunscreen), benzocaine (used in local anaesthetics) and sulfa drugs.

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