Patient Case: Borderline (Dimorphous) Leprosy
A 35-year-old farmer from a mountainous region presents to a dermatology clinic with multiple skin lesions that have been gradually increasing in size and number over the past two years. He describes areas of numbness and tingling in his arms and legs, along with muscle weakness in his hands. He has no history of fever or systemic illness but reports that his symptoms have progressively worsened.
On examination, the patient has several asymmetrically distributed, hypopigmented and erythematous plaques with poorly defined borders, some of which show partial loss of sensation. There is noticeable thickening of the right ulnar and left common peroneal nerves, with tenderness on palpation. His eyebrows appear sparse, and there is mild clawing of his right hand.
A slit-skin smear reveals a moderate number of acid-fast bacilli, and a skin biopsy shows both tuberculoid granulomas and foamy histiocytes, confirming borderline (dimorphous) leprosy. Given the unstable nature of the disease, the patient is started on multidrug therapy (MDT) with rifampicin, dapsone, and clofazimine for at least 12 months. He is counseled on the risk of disease progression or reversal reactions and referred for nerve function assessment to prevent further disability. Contact tracing is initiated to screen his close contacts for leprosy.
- What is a key clinical feature of borderline (dimorphous) leprosy?
A) Single, well-defined hypopigmented lesion with sensory loss
B) Multiple, asymmetrical hypopigmented and erythematous plaques with partial sensation loss
C) Diffuse skin infiltration with leonine facies
D) Painful vesicular rash with systemic symptoms - Why is borderline leprosy considered an unstable form of the disease?
A) It can shift toward either tuberculoid or lepromatous leprosy based on immune response
B) It resolves spontaneously without treatment
C) It is highly contagious and rapidly progresses to systemic disease
D) It is caused by a different strain of Mycobacterium leprae - Which nerve is commonly affected in borderline leprosy, leading to hand deformities?
A) Ulnar nerve
B) Phrenic nerve
C) Optic nerve
D) Radial nerve - What is the recommended treatment for borderline leprosy?
A) Rifampicin and dapsone for 6 months
B) Rifampicin, dapsone, and clofazimine for at least 12 months
C) Isoniazid and rifampicin for 9 months
D) Acyclovir and valacyclovir for 2 weeks
Answers
- Answer: B) Multiple, asymmetrical hypopigmented and erythematous plaques with partial sensation loss
- Borderline (dimorphous) leprosy presents with multiple asymmetrical skin lesions that show variable sensory loss due to partial nerve involvement. This differentiates it from tuberculoid leprosy, which has a single well-defined lesion (A), and lepromatous leprosy, which shows diffuse skin infiltration and leonine facies (C). Painful vesicular rashes (D) are not associated with leprosy.
- Answer: A) It can shift toward either tuberculoid or lepromatous leprosy based on immune response
- Borderline leprosy is immunologically unstable and can progress toward tuberculoid leprosy (stronger immune response) or lepromatous leprosy (weaker immune response). It does not resolve spontaneously (B) and is not the most contagious form (C). There is no evidence of it being caused by a different strain of M. leprae (D).
- Answer: A) Ulnar nerve
- The ulnar nerve is one of the most commonly affected nerves in leprosy, leading to hand deformities such as claw hand. The phrenic nerve (B) controls the diaphragm and is not affected in leprosy. The optic nerve (C) is rarely involved, and the radial nerve (D) is less frequently affected than the ulnar nerve.
- Answer: B) Rifampicin, dapsone, and clofazimine for at least 12 months
- Borderline leprosy is treated as a multibacillary form with rifampicin, dapsone, and clofazimine for at least 12 months due to the higher bacterial load and risk of progression. Rifampicin and dapsone for 6 months (A) is used for tuberculoid leprosy. Isoniazid and rifampicin (C) treat tuberculosis, and acyclovir with valacyclovir (D) treats viral infections like herpes, not leprosy.
