Multiple nerve abscesses: An unusual manifestation of lepra reaction in a patient with borderline leprosy
Correspondence Address: Source of Support: None, Conflict of Interest: None DOI: 10.4103/0028-3886.193787
Source of Support: None, Conflict of Interest: None
Leprosy is still one of the common and treatable causes of peripheral neuropathy in many resource-constrained countries including India. Official figures from 103 countries from 5 World Health Organization regions show the global registered prevalence of leprosy to be at 180,618 at the end of 2013; during the same year, 215,656 new cases were reported.
Leprosy is characterized by a triad of hypoesthetic skin lesions, thickened peripheral nerves, and positive skin smear for Mycobacterium leprae. In leprosy, all functions of a peripheral nerve (sensory, motor, and autonomic) are impaired. Sensory functions are most severely and universally impaired. Different patterns of nerve involvement are seen in different types of leprosy. In tuberculoid leprosy, involvement of small cutaneous nerves of cooler parts of the body leads to a patchy sensory loss. Disease is restricted to the territory of single nerve trunk. In lepromatous leprosy, there is a widespread and extensive involvement. Patients with lepromatous leprosy usually have symmetrical, distal peripheral neuropathy. Damage to nerve trunks may initially be in the pattern of mononeuritis multiplex but later becomes bilaterally symmetric. Borderline leprosy has a very high propensity to involve multiple nerve trunks, producing a picture akin to mononeuritis multiplex. Usually, peroneal and posterior tibial nerves in the lower limbs, and ulnar nerve in the upper limbs, are most frequently affected., In fact, leprosy, in India, is still the most frequent cause of mononeuritis multiplex.
During the course of leprosy, immunologically mediated exacerbations of inflammation, known as reactions, occur in up to 25% of patients with paucibacillary leprosy, and in as much as 40% in multibacillary leprosy., Nerve abscesses are infrequently observed complications of tuberculoid and borderline leprosy. Most of incidences of nerve abscesses have been observed in the form of isolated case reports.,
We report an unusual case of a patient suffering from leprosy presenting with multiple abscesses of the median nerve as a manifestation of reversal reaction.
A 21-year-old farmer presented with complaints of weakness and sensory loss involving the right upper limb for 2 years. He had been diagnosed as a case of leprous mononeuritis multiplex and had been receiving a multidrug therapeutic regimen. Review of the old records revealed thickening of the right median nerve, along with weakness and sensory loss. Slit-skin smear test had demonstrated the Mycobacterium leprae baciili. Three days prior to the current admission, the patient developed painful cystic swellings along the long axis of the flexor surface of the right forearm; the swellings were tender, three in number, with erythema of the overlying skin. The swellings were along the course of the median nerve [Figure 1]. Exfoliation was noted over the right thumb. The median nerve was thickened; 4–5 days after admission, the tenderness as well as the size of the swellings increased. Slit-skin smear test was negative. All blood biochemical parameters were normal. Nerve conduction in the right upper limb was not recordable and was normal in the other limbs. Ultrasonography (USG) of the right median nerve revealed thickening of the nerve with loss of the normal fascicular pattern and multiple abscess formation along the course of the nerve. Magnetic resonance neurography also revealed the thickened right median nerve and multiple abscesses in the nerve trunk [Figure 2]. The patient at this stage was treated with methylprednisolone for 5 days but without much benefit. The abscesses increased in size. Percutaneous drainage of an abscess was attempted and about 5 ml of pus was drained. The pus was sterile; however, an acid-fast Bacilli was demonstrated [Figure 2]. The abscess again increased after a few days. The patient was subjected to surgery and all the abscesses were excised. The abscess tissue revealed a well-formed granuloma involving nerve fibers. Fite stain for lepra bacilli in the granuloma was negative. Multidrug therapy was continued. After 3 months of follow-up, the patient was symptomatically much better with intact motor functions of the right median nerve.
In our case, nerve abscesses developed almost 2 years after the initiation of the multidrug therapy for leprosy. This was an unusual presentation of a Type 1 lepra reaction.
Nerve abscesses are frequently reported in patients with paucibacillary leprosy, particularly in tuberculoid and borderline forms., Tuberculoid leprosy is characterized by an active immune reaction against M. leprae; active cell-mediated immunity restricts the disease to a few peripheral nerves or skin lesions. Borderline leprosy has features suggestive of the 2 polar forms. Borderline tuberculoid leprosy is close to tuberculoid leprosy, whereas borderline lepromatous leprosy is close to lepromatous leprosy. In tuberculoid and borderline leprosy, there is a T-cell orchestrated destruction of perineurium of a peripheral nerve along with damage of Schwann cells and axons, and formation of epithelioid granulomas., In severe cases, inflammatory changes and liquefaction of the granuloma lead to caseous necrosis. Multiple caseating lesions within the nerve may coalesce to form a nerve abscess, usually a cold abscess.
Patients with borderline leprosy have an unstable immune status against M. leprae. In borderline leprosy, the host's cell-mediated immunity can progress unpredictably to either pole (either towards the tuberculoid type or towards the lepromatous type). A downgrading reaction (a shift toward the lepromatous pole) with a deficient immunity allows extensive multiplication of the M. leprae in the nerve trunks. Following multidrug therapy, an upgrading or reversal reaction (a shift to the tuberculoid pole) takes place leading to an intense inflammatory response and subsequent extensive damage to the peripheral nerves. Reactions in leprosy are treated with oral corticosteroids.,, These inflammatory changes may, at times, be intense enough to produce nerve abscesses.
A type 1 lepra reaction or reversal reaction is a kind of delayed hypersensitivity reaction that is seen in both paucibacillary leprosy and multibacillary leprosy. During leprosy reactions, the cutaneous lesions become swollen, erythematous, and tender, whereas acute inflammatory changes of the peripheral nerves lead to pain, tenderness, and loss of function. Type 1 lepra reactions usually occur within the first 6 months of starting a multidrug therapeutic regimen. Infrequently, delayed reaction can be seen long after the completion of multidrug therapy. In a reversal reaction, there is an enhanced cell-mediated immune reaction against the M. leprae. Type 1; or, reversal reaction is seen in patients with tuberculoid and borderline leprosy. In its extreme form, Type 1 lepra reactions may cause severe nerve damage and may lead to nerve abscess formation, as has been seen in our patient. The histopathological changes of lepra-1 reaction are a marked increase in the size of the epithelioid granuloma, heavy fresh infiltration of the lymphocytes, and the occurrence of extracellular edema. Occasionally, there is liquefaction of the granuloma leading to caseous necrosis, and rarely, to the formation of nerve abscess.,
High-resolution ultrasound imaging is an important method to evaluate nerve abscesses in patients with leprosy. An ultrasound imaging in a nerve abscess shows diffuse thickening of the nerve with a hypoechoic texture and a cystic lesion with the internal debris. Magnetic resonance imaging is helpful in differentiating many mass lesions of peripheral nerves such as a schwannoma, neurofibroma, lipoma, ganglion cyst, and perineurioma. Leprosy-associated nerve abscess usually reveals signal changes of an abscess with peripheral contrast enhancement of the abscess wall and inflammatory thickening of the whole nerve trunk.,,
Once diagnosed, a leprosy-associated nerve abscess often requires surgical decompression and drainage of the abscess for possible restoration of nerve function. In our case, surgical drainage of the abscess led to prompt relief from symptoms and recovery of nerve functions.
In conclusion, a nerve abscess can be a disabling manifestation of lepra reaction in a patient with leprosy. A prompt diagnosis and surgical drainage of the abscess led to rapid restoration of nerve function.
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[Figure 1], [Figure 2]