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A previously healthy young man in his 20s developed ring-like lesions on his torso and other areas of his body and could no longer straighten out his fingers, clinicians recounted in .

When he presented for a dermatology evaluation, he reported that the affected skin was numb and tingling, according to the case report from Saadeddine Saad, MD, of Baylor Scott & White Health in Temple, Texas, and colleagues.

In taking the patient's history, clinicians learned that he had left his native Samoa 4 years previously to immigrate to the U.S. The lesions had first developed on his right ankle, he said, and then emerged on his face, trunk, and limbs over the prior 3 months. He denied use of prescribed medications or herbal supplements.

On performing a physical exam, the team noted that the patient had numerous tattoos and annular reddened plaques on his face, chest, back, arms, and legs. The affected areas of skin were insensitive to temperature changes. Both arms had palpable thickened auricular and ulnar nerves, and both hands were affected by a claw-hand deformity. Foot drop was evident in both feet.

The team ordered tests for rapid plasma reagin, antinuclear antibodies, and rheumatoid factor; all returned negative results.

The patient underwent punch biopsies of two plaques on his back. Evaluation of those tissue samples "revealed granulomatous periadnexal and perivascular dermatitis with diffuse granulomatous infiltrate and foamy histiocytes," the case authors noted.

Acid-fast bacilli stains and mycobacterial polymerase chain reaction (PCR) tests returned negative results. There was no evidence of fungal organisms or Mycobacterium leprae on a Fite Faraco stain.

The team performed a skin biopsy of the patient's arm and sent the tissue sample to the U.S. National Hansen's Disease Program; results of a quantitative PCR assay were positive for M. leprae and the patient was diagnosed with multibacillary leprosy.

"The key to the correct diagnosis was the presence of skin lesions with associated hypoesthesia and peripheral nerve abnormalities in a patient from Samoa, where leprosy is endemic," Saad and co-authors explained.

They treated the patient with prednisone (60 mg daily) for 5 days. Then treatment was switched to prednisone (5 mg daily) and methotrexate (20 mg weekly) after the patient developed a leprosy reaction marked by worsening of the paresthesia and erythema in the existing skin plaques.

Six days later, clinicians initiated monthly treatment with rifampin (600 mg), moxifloxacin (400 mg), and minocycline (100 mg), along with amitriptyline (10 mg) to manage his nerve pain. After 3 months of antibiotic treatment, they noted considerable improvement in both skin plaques and neuropathy symptoms.

Eleven months after he presented for care, "the patient underwent tendon transfer surgery with a fascia lata graft to the second through fifth fingers on his left hand," the clinicians said. This was followed by 3 months of occupational therapy.

At the patient's most recent follow-up visit to the clinic, the team reported that "he had taken 9 of 12 planned months of rifampin, moxifloxacin, and minocycline and was taking prednisone (5 mg daily) and methotrexate (20 mg weekly)."

Discussion

"Leprosy, also known as , is an infection caused by the acid-fast bacilli M. leprae and Mycobacterium lepromatosis, which are obligate intracellular organisms that cannot be cultured on artificial media," wrote Saad and co-authors.

Worldwide, leprosy is diagnosed in about 200,000 people every year. Humans are the main vectors of leprosy infection, with 200 to 300 individuals diagnosed yearly in the U.S. However, the nine-banded armadillo also acts as a zoonotic reservoir in the U.S., authors noted.

Notably, both M. leprae and M. lepromatosis DNA were found in red squirrels with leprosy-like lesions in the British Isles in 2016, leading those researchers to identify as a reservoir for leprosy there.

While infectious aerosols created by coughing and sneezing represent the most common transmission pathway, "skin contamination with tattooing and vertical transmission have been reported," the case report authors said.

Risk of infection is increased in those who have had close contact with a leprosy patient, are immunosuppressed or immunodeficient, individuals who are genetically predisposed to the infection, and those who have had exposure to armadillos, wrote Saad and colleagues.

There are several systems for leprosy. The Ridley-Jopling classification system is based on the clinical features of the disease, which range from a single hypopigmented skin macule to generalized disease. This system defines five categories of leprosy: tuberculoid, borderline tuberculoid, borderline, borderline lepromatous, and lepromatous.

The World Health Organization (WHO) developed a simplified classification with only two categories: multibacillary if there are six or more skin lesions and paucibacillary if there are fewer than six.

Differential diagnoses to consider include interstitial granulomatous dermatitis, granuloma annulare, granulomatous dermatitis of immune deficiency, granulomatous drug eruption, psoriasis, and mycobacterial or fungal infections.

Clinical features used to diagnose leprosy reflect typical signs of skin lesions with hypoesthesia and nerve enlargement, the authors noted. "Some patients may develop an immune response to M. leprae, called a leprosy reaction, which presents as urticarial swelling of skin lesions, fever, neuritis, erythema nodosum, and permanent loss of motor and sensory nerve function," they noted. These immune reactions due to an immune response between the host and M. leprae, can occur before, during, or after treatment for leprosy.

Of the various approaches to diagnosing leprosy, a skin biopsy is the only test that provides a definitive diagnosis. In cases where biopsy is nondiagnostic, Saad and colleagues suggested that use of PCR testing of a tissue sample may be helpful. The sensitivity of a PCR test ranges from 34% to 80% in patients with fewer than six skin lesions, and exceeds 90% in patients with six or more lesions. Specificity of PCR testing is up to 100% for both paucibacillary and multibacillary leprosy.

Case authors emphasized the important role of timely diagnosis and treatment, in order to minimize the transmission risk, as well as the disability and negative psychosocial effects associated with the disease.

According to WHO recommendations, patients with leprosy should receive treatment with dapsone, rifampin, and clofazimine for a duration of 6 months for paucibacillary leprosy and for 12 months for multibacillary disease. Saad and co-authors added that compared with the WHO regimen, 12 to 24 months of monthly treatment with rifampin, moxifloxacin, and minocycline is similarly effective, and associated with fewer side effects and better adherence, but at about four times the cost.

After treatment completion, relapse rates with the two regimens appear to be comparable, the authors noted. For the WHO multidrug therapy, 0.77% of patients with multibacillary leprosy and 1.07% of those with paucibacillary leprosy had relapses. Risk of a relapse is increased in patients with a high mycobacterial load, greater number of skin lesions, inadequate treatment duration or regimen, and poor adherence to treatment, the group concluded.

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