Discussion:
Pure neuritic leprosy is an uncommon presentation of leprosy. However,
in Indian subcontinent, 4.6-17.7% of leprosy patients present with
nerve involvement without skin lesions [4]. Sensory, motor and/or
autonomic deficit occurs along the distribution of the affected
nerve.[5] Ulnar nerve and lateral popliteal nerve are the most
common nerves involved in upper limbs and lower limbs respectively,
though, any nerve can be involved [3].They are frequently
misdiagnosed because of absence of skin lesions and negative slit skin
smear and can present with Grade II disability as initial presentation
[6]. Nerve biopsy is the gold standard for diagnosis but it is an
invasive procedure with possible complications like nerve damage. The
non-invasive high quality electrophysiological studies are helpful in
the diagnosis of leprosy. [7]
On follow up, 15-35% of pure neuritic leprosy patients develop visible
skin lesions which may indicate prolonged neuritic phase preceding the
appearance of cutaneous lesions and most of these lesions are confirmed
as borderline tuberculoid type histopathologically [8-11]. Sudden
appearance of new lesions can occur due to fluctuations of cell mediated
immunity in untreated or treated cases of leprosy. Some authors
considered that the new skin lesions developed were possibly
manifestation of reversal reaction [9-12]. Absence of visible skin
lesions in patients is probably related to the deep location of
granuloma in the dermis which could be manifested during reactions. This
is yet to be proven. Due to absence of preexisting lesions to manifest
inflammatory process, the diagnosis of type 1 reaction in pure neuric
leprosy is often missed, under-recorded and under-reported [3].
In our patient, the diagnosis of pure neuritic leprosy was made by
clinical examination performed by an experienced clinician combined with
nerve conduction studies and the type 1 lepra reaction by increased
tingling sensation with the development of edematous and erythematous
new lesion over left cheek and pedal edema. This was correlated
histopathologically with biopsy from these sites and resolution of pedal
edema and lesion over the cheek after administration of oral
corticosteroids. The clinicians should be aware about unusual
presentation of type 1 reaction in pure neuritic leprosy so that
unnecessary work-ups are avoided and disabilities are prevented.