Infectious Diseases Case of the Month #8

A 47 yo hispanic male was seen in infectious diseases clinic for a rash.

The patient was born in Puerto Vallarta, Mexico where he had resided the entirety of his life until moving to Warden, Washington (Central Washington) approximately seven months prior to his clinic visit.

He had first developed a rash on his right cheek five months prior to his clinic presentation. Subsequently, he developed focal areas of rash above his left eyebrow and on his extremities. There may have been numbness or discomfort associated with areas of the rash. At the time of his examination there was a raised erythematous plaque encompassing most of his right cheek, a 2-3 cm plaque over his left eyebrow, a 3-4 somewhat annular lesion of his proximal right thigh (similar to that pictured at left). Several smaller areas of rash were elsewhere on his extremities. The rash had not responded to prior courses of oral antibiotics nor topical corticosteroids.

The patient had worked with dairy cattle as his occupation both in Mexico and currently in Warden. He often would drink the fresh unpasteurized milk. Some of the cattle at Warden had recently died but he did not think their rate of death was excessive. He was unaware of tuberculosis amongst the cattle either in Mexico or in Washington.

The patient was married though his wife and children remained in Mexico. He had not previously had significant medical illnesses, had received no blood transfusions, and denied risky sexual behaviors. He felt well, was afebrile, and denied chills, sweats, weight loss, cough, or other indications of systemic illness.

Laboratory evaluation included WBC 5.4, Hgb 14.8, Plts 204. ANA was negative.

The patient underwent a skin biopsy. Routine H & E stains showed areas of vaguely granulomatous inflammation. Ziehl-Neelsen stains were negative. A photomicrograph of the Fite stain is pictured at left. Cultures were subsequently negative.

What organism is most likely to have caused this patient's illness?
Diagnosis: Mycobacterium leprae

This patient had Hansen's Disease caused by Mycobacterium leprae.

Hansen's Disease or leprosy is a disease of great antiquity and one whose deformities and disabilities have been associated with great social stigmatization. Formerly a disease of considerable prevalence, its prevalence has been significantly reduced through WHO programs providing aggressive MDT regimens. Currently it remains endemic only in Brazil, and areas of Africa and the Indian subcontinent. In the United States there is an incidence of leprosy of 100-200 cases per year, almost exclusively in immigrants.

The mode of transmission of leprosy remains incompletely known. It is believed that it is spread from human to human primarily via droplet aerosols. Incubation period is uniquely long amongst bacterial diseases averaging 5 to 7 years and can be up to 40 years.

The disease primarily involves the skin with morbidity relating to the organism's unique tropism for peripheral nerves. Nerve damage results in neuropathic deformities with resultant disabilities. A spectrum of illness occurs likely related to host immunologic factors. Disease ranges from a paucibacillary form (tuberculoid leprosy) to a multibacillary form (lepromatous leprosy) with intermediate borderline forms of disease.

The patient described likely had a borderline form of disease. Diagnosis was based on clinical and pathologic findings including the patient's altered sensation, the somewhat linear inflammatory infiltrates (suggesting occurrence along peripheral nerves (see upper photomicrograph at left)), and observed perineural inflammation, (see lower photomicrograph at left). Staining characteristics of the organism (negative Ziehl-Neelsen, positive Fite) were also suggestive. Unlike the other mycobacteria species listed in the preceding vignette, Mycobacterium leprae cannot be cultured on laboratory media so negative cultures were further evidence for the diagnosis of leprosy.

The patient was referred to the Hansen's Disease Clinic in Seattle for further evaluation and therapy. The Seattle clinic is one of 16 such clinics of the National Hansen's Disease Programs (see map at left). There he received treatment with dapsone, clofazimine, and rifampin. Within six months of initiation of treatment his skin lesions had dramatically faded. He was lost to follow-up when he returned to Mexico several months later.

Ref:   Bogglid, AK, et al, Leprosy: A primer for Canadian physicians, CMAJ, 170 (1): January 6, 2004

Myron Whitehead, MD (WVC) and James Harnisch, MD (Seattle NHDP) also contributed to this vignette.


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