According to data from the World Health Organization (WHO), the number of new cases of Hansen’s disease (HD, or leprosy) identified worldwide declined by about 20% from 2003 to 2004. At least 116 of 122 countries once considered leprosy—endemic have achieved a prevalence rate of less than one case per 10,000 population.1,2
Meanwhile, the number of active HD infections in the United States catalogued through the CDC and the National Hansen’s Disease Program (NHDP) rose from 76 cases in 2000 to 166 in 2005, with an additional 137 cases in 2006 (the most recent year for which complete figures are available).3,4 Currently, 6,500 US residents are known to have HD, of whom 3,300 require care for active disease.3
Accurate diagnosis and straightforward, aggressive treatment can mean certain cure for this dreaded disease, as it is responsive to a combination of available drugs. For primary care providers in the US, familiarity with this condition can play a role in eliminating it altogether.
Background and Etiology
HD is believed to have originated in East Africa with the pseudonym of leprosy, from the Greek lepi, meaning “fish scales.” Although HD is one of the oldest known human infections, it is not well understood by many Western health care providers. Once considered highly contagious and easily transmissible, HD has proven to be neither: 95% of the human population is not susceptible to the responsible pathogen.3 HD retains its reputation as a devastating illness when left untreated, however, with sequelae often including significant sensory and motor dysfunction.5
Leprosy is a chronic bacterial disease caused by Mycobacterium leprae. Mycobacterium is the same rod-shaped, acid-fast bacillus (AFB) implicated in pulmonary tuberculosis, cutaneous tuberculosis, and numerous cutaneous nontuberculoid infections.6,7
HD transmission is believed to occur almost exclusively by nasal droplet, inhaled by way of others’ nares or lungs. Research continues in possible transmission by skin-to-skin contact.8,9
Leprosy is particularly challenging for immunocompromised persons, such as those with HIV/AIDS or tuberculosis. According to data from the NHDP, HD in the US is found primarily among undocumented immigrants who live in close quarters. Cases considered “home-grown” rather than “imported”5 are most commonly diagnosed in Hawaii and in a swath from Texas to Georgia and south toward Florida. Pockets of HD incidence are also found in California, New York, and Massachusetts.4
Clinicians’ lack of familiarity with HD and its relative rarity in the US help explain why diagnosis and treatment are commonly delayed. As a patient’s disease progresses from an insidious, gradual, and relatively painless onset, the primary care provider may be grappling with an extensive differential diagnosis (see “Differential Diagnosis for Hansen’s Disease [Leprosy],”10,11 below). Even after confirming a diagnosis of HD, the provider must contend with a lack of information and misinformation about HD among staff members, the patient’s family, and society at large, as well as the associated stigma. Patient education and effective treatment are of comparable importance.
Patient Presentation and History
A 40-year-old Latino man presented to a primary care provider with a well-demarcated, erythematous patch on his right upper back that had raised outer edging and faint flaking. The patch was surrounded by several smaller but similar asymmetrical macules. The patient denied pruritus but stated that the area “felt funny.” He said the lesion might have been spreading during the previous several months, but he could not be certain because of its location.
The man denied any medication use except for a topical antibiotic ointment he had applied to the affected area with no improvement. His provider made a diagnosis of tinea corporis and prescribed an antifungal cream, naftifine. After two weeks without results, the patient was referred to a dermatologist.
During the assessment, it became apparent that the patient was experiencing numbness in his fingertips and general muscle weakness in his arms. A KOH prep was difficult to obtain, as the lesion site was somewhat smooth. Any dermatophytes that may have been present had been eliminated by the naftifine, and KOH results were negative.
A 5.0-mm punch biopsy from the largest lesion was ordered. A preliminary diagnosis of sarcoidosis (chronic inflammation with an unusual skin manifestation) was made, with serious consideration given to early cutaneous T-cell lymphoma (mycosis fungoides). A high-potency steroid was prescribed for five days’ use, twice daily.
On his return to the dermatologist, the patient reported that the site was no better. He was informed that the dermatologist and the pathologist, both with considerable experience, had detected no bacilli or dermal nerve infiltration in the tissue sample but had observed abundant lymphocytic infiltration. This finding, coupled with the patient’s decreased sensation, muscle fatigue, and status as a recent immigrant from a South American country, led to an initial diagnosis of borderline leprosy (BB).