Which of the following diseases is related to Fernandez's reaction?

Appeared in: DSSSB 12 August 2024

Explanation

Fernandez's reaction is the early phase of the lepromin test, a skin test used in the assessment of leprosy.
It manifests as redness and swelling (erythema and induration) at the injection site, peaking at around 48 hours.
This reaction is a classic example of a delayed-type (Type IV) hypersensitivity response to antigens from Mycobacterium leprae.
A positive Fernandez reaction indicates that the patient has some level of cell-mediated immunity against the leprosy bacillus.

Option B: Rubella, a viral disease, is diagnosed using serological tests to detect specific IgM and IgG antibodies in the blood, not with a skin reaction test like Fernandez's.
Option C: Malaria is a parasitic disease caused by Plasmodium species. Its diagnosis relies on identifying the parasite in a peripheral blood smear or using rapid antigen detection tests.
Option D: Cholera is a bacterial infection of the intestine. It is diagnosed by isolating Vibrio cholerae from a stool sample via culture or by using rapid dipstick tests on stool.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Lepromin test and its biphasic reactions (Fernandez and Mitsuda) in Leprosy as background academic context rather than a clinical decision trigger.
The lepromin test, including the Fernandez reaction, is not for diagnosing leprosy but for classifying it and determining prognosis. It helps differentiate between the paucibacillary (Tuberculoid) and multibacillary (Lepromatous) forms of the disease.
A positive reaction (good cell-mediated immunity) is seen in Tuberculoid leprosy, which has a better prognosis. A negative reaction (poor immunity) is characteristic of Lepromatous leprosy, which is more severe and infectious.
This classification is crucial for determining the correct multidrug therapy (MDT) regimen and duration of treatment for the patient.

How to Approach the Question

First, identify the key term in the question stem: 'Fernandez's reaction'.
Recognize this as a specific clinical test or sign.
Access your knowledge base to recall that the Fernandez reaction is the early phase of the lepromin test.
Connect the lepromin test to its specific disease association, which is Leprosy (Mycobacterium leprae).
Systematically evaluate the given options. Rule out Rubella, Malaria, and Cholera by recalling their primary diagnostic methods (serology, blood smear, and stool culture, respectively).
Confirm that Leprosy is the only disease on the list associated with the lepromin test and, by extension, Fernandez's reaction.

Concept Tested & Keywords

Concept Tested: Lepromin test and its biphasic reactions (Fernandez and Mitsuda) in Leprosy.
Stem keywords: Fernandez's reaction, diseases
Lead-in keywords: related to

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E6 Medicine Harrison 22e Part 1 p. 1449-1451

E6 Microbiology Essentials Sastry 4e Part 2 p. 88-90

Practise the full DSSSB 12 August 2024

Attempt every question from this paper in a timed mock, then review the full solution for each one.