Answer to last month's Clinical Quiz

Question:

A 30 years old gentleman was diagnosed to have chancre (primary syphilis) and agreed to receive penicillin treatment. With no history of penicillin allergy, Procaine penicillin G 1.2gm IMI daily was started and the initial three doses were uneventful with only mild febrile reaction on the first day. On the fourth day, the patient presented with maculo-papular rash distributed over his trunk and proximal limbs. They were intensely itchy but the patient was otherwise well, afebrile, with neither mucosal involvement nor any systemic symptoms. He was not taking any other medication.

Answer: C. Penicillin reaction

The diagnosis of penicillin reaction is most likely in this patient. The early stage of syphilis makes rash of secondary syphilis unlikely; absence of systemic upset clinically ruled out viral exanthems; the maculopapular nature of the rash and sudden onset makes eczema unlikely.

Penicillin is the treatment of choice for all stages of syphilis. However problems might arise when patients are penicillin allergic or intolerant. The frequency of penicillin adverse reaction in the general population varies widely from 0.7% to 10%, depending much on the diagnostic and sampling method. Generally penicillin reactions are classified into immediate (type I), late (type II, III and IV), and idiopathic. The immediate (type I) is the most dangerous type which may be associated with systemic manifestations of anaphylaxis, hence could be life threatening. Our patient's penicillin action is the idiopathic type, with onset usually after 72 hours of exposure, presents as maculopapular or morbilliform rashes, which is reported to happen in 1% to 4% of patients and is relatively harmless.

The prevention of occurrence of penicillin reaction depends very much on a careful history taking. Questions to be asked may include: detail of the reaction, time lag between administration and reaction, route of administration, why the patient was receiving penicillin, what other medications the patient was concomitantly taking and whether the patient has other drug intolerance. Detailed explanation of treatment choices, benefits and risks to patients with syphilis is essential before deciding on the most appropriate treatment.