Dermatology Online Journal

Clinical pearl for the diagnosis of Hansen disease
Sunaina Bhuchar MD, C Stanley Chan MD, Mohsin R Mir MD, Paul Subrt MD, Jaime A Tschen MD, W Edward Collins MD, Sylvia Hsu MD
Dermatology Online Journal 15 (12): 7

Department of Dermatology, Baylor College of Medicine, Houston, Texas. shsu@bcm.edu

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Introduction

Leprosy is an indolent progressive disease caused by infection with Mycobacterium leprae. The primary skin lesion is hypopigmented or erythematous and often associated with decreased sensation due to its predilection for peripheral cutaneous nerves. However, the clinical presentation is highly variable and determined by the type of immune response mounted against the bacteria. Leprosy may thus be initially misdiagnosed as other dermatologic conditions and should be considered in the differential diagnosis of recalcitrant dermatoses sparing the axillary vault.

History

A 71-year-old Caucasian man presented to the dermatology clinic with a diffuse, non-pruritic rash on his back and abdomen, and he complainted of swollen hands. The rash initially began as a small patch on his right buttock and left arm with eventual progression to his abdomen and back over several months, despite the use of potent topical corticosteroids. Review of systems was significant for pain and loss of sensation in his left foot for over 5 years which had been worked-up by numerous physicians with varying diagnoses. However, there were no sensory changes within the skin lesions. Otherwise, the patient's past medical and surgical history were unremarkable. His medications, clothing, soaps, and level of sun exposure had not recently changed. Of note, the patient is a missionary who had previously spent fourteen years in rural and urban areas of Guyana, South America.

Figure 1	Figure 2
Figure 1. Ill-defined, symmetric erythematous plaques of trunk. (previous biopsy sites are present) Figure 2. Note the axillary vault sparing

Figure 3	Figure 4
Figure 3. Predominantly foamy histiocytes located within the dermis with a Grenz zone present Figure 4. Lymphohistiocytic infiltrate surrounding a nerve fiber

Figure 5
Figure 5. Fite stain demonstrating numerous acid fast bacilli arranged in globi

Physical exam showed extensive ill-defined symmetric, erythematous, eczematous plaques involving his back and extending to his abdomen and proximal extremities. The axillae were notably spared. Basic musculoskeletal and neurologic examination revealed edema of the digits and decreased sensation of the left foot. Punch biopsy from the back revealed a lymphohistiocytic infiltrate, notably tracking along a cutaneous nerve. Fite stain demonstrated numerous bacilli with globi formation.

Discussion

Leprosy, also known has Hansen disease, is a slowly progressive granulomatous disease caused by Mycobacterium leprae, a highly infective organism of relatively low virulence and pathogenicity [1]. Known to have a predilection for the cooler areas of the body, M. leprae affects mostly the skin, superficial peripheral nerves, anterior chamber of the eyes, and the testes.

Although the global prevalence of leprosy has decreased significantly over the past 20 years [2], it still remains an endemic problem in some tropical and subtropical countries [3]. In 2005, Guyana-where our patient had lived for fourteen years-reported the second highest prevalence of leprosy in the Americas of 1.3 per 10,000 people [4].

The Seventh Meeting of the WHO Expert Committee on Leprosy in 1997 defined three cardinal signs by which to diagnose leprosy [5]:

1) Hypopigmented or reddish skin lesions with loss of sensation

2) Involvement of the peripheral nerves as demonstrated by their thickening and associated loss of sensation

3) Skin-smear positive for acid-fact bacilli.

The dermatological manifestations of leprosy vary widely and reflect the type of immune response-cell-mediated versus humoral-mounted by the host against the bacteria [6, 7]. The polymorphic nature of Hansen disease has inspired the development of various classification systems. The most comprehensive of these is the Ridley-Jopling system, which characterizes leprosy along a granulomatous continuum from tuberculoid to lepromatous leprosy (see Table 1) [8].

Our patient appears to fit the clinical description of borderline lepromatous disease, given his extensive, ill-defined skin lesions, his intractable nerve involvement, and the fusiform changes of his digits. His biopsy findings of lymphocytes and macrophages perineurally and numerous bacilli visualized on Fite stain support a diagnosis of borderline leprosy.

The range of cutaneous manifestations in leprosy is clearly vast, and thus it can be initially misdiagnosed as other skin diseases [9], especially in non-endemic areas. While our patient exhibited many of the classic findings of Hansen disease, his dermatologic presentation was notable for axillary-sparing. Leprosy tends to favor cooler areas of the body, and thus axillary sparing can be a clue to aid in its diagnosis. Allergic contact dermatitis due to clothing and textiles classically also spares the axillary vault [10]. This case supports the significance of Hansen disease in the differential diagnosis of contact dermatitis, especially when the patient presents with neuropathy, or when the dermatitis is recalcitrant to conventional therapies.

References

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2. Moschella SL. An update on the diagnosis and treatment of leprosy. J Am Acad Dermatol. 2004; 51(3):417-26. [PubMed]

3. Canizares O, Harman R, Adriaans B. Leprosy. In: Canizares O, Harman R, editors. Clinical tropical dermatology. 2nd ed. Boston: Blackwell Scientific, 1992: 165-200.

4. Status of Leprosy in the Region of the Americas. Brochure. World Health Organization. < http://www.paho.org/English/AD/DPC/CD/lep-americas.pdf >.

5. WHO Expert Committee on Leprosy. Rep. no. 7. 1997. World Health Organization. https://www.who.int/lep/resources/Expert.pdf>

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7. Anderson H, Stryjewska B, Boyanton BL, Schwartz MR. Hansen disease in the United States in the 21st century: a review of the literature. Arch Pathol Lab Med. 2007;131(6):982-6. [PubMed]

8. Ridley DS, Jopling WH. Classification of leprosy according to immunity. A five-group system. Int J Lepr Other Mycobact Dis. 1966;34(3):255-73. [PubMed]

9. Hartzell JD, Zapor M, Peng S, Straight T. Leprosy: a case series and review. South Med J. 2004; 97(12):1252-6. [PubMed]

10. Vivier, AD. Atlas of clinical dermatology. 3rd edition. Churchill Livingstone, 2002.

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