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Skin nontumor

Infectious disorders

Leprosy

Author: Mowafak Hamodat, M.B.Ch.B., M.Sc.

Last author update: 1 March 2011

Last staff update: 21 June 2022

Copyright: 2002-2024, PathologyOutlines.com, Inc.

PubMed Search: Leprosy infection [title]

Table of Contents

Cite this page: Hamodat M. Leprosy. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/skinnontumorleprosy.html. Accessed December 25th, 2024.

Definition / general

Chronic cutaneous infection caused by Mycobacterium leprae and Mycobacterium lepromatosis (CDC: Mycobacterium lepromatosis Lepromatous Leprosy in US Citizen Who Traveled to Disease-Endemic Areas [Accessed 26 November 2018])

Terminology

Also called Hansen disease

Epidemiology

Most U.S. cases occur in immigrants
Worldwide distribution due to travel and migration but endemic in tropics

Clinical features

Mycobacterium leprae is an obligate intracellular gram positive and weakly acid fast organism
The complexity of presentation is related to the varied immunologic responses
The incubation period is usually 3 - 5 years
Tuberculoid leprosy occurs in individuals with good cell mediated immunity; patients develop granulomatous response
Lepromatous leprosy occurs in individuals with poor cell mediated immunity; do not develop a granulomatous response
Borderline leprosy is an intermediate form between tuberculoid and lepromatous leprosy
Transmitted by nasal discharge and digital impregnation of skin, as bacilli can be carried under nails and are inoculated under the skin by scratching
Lucio phenomenon is seen in Mexican and Central American patients who present with untreated, diffuse, non nodular lepromatous leprosy with hemorrhagic infarct
Planter lesions are at increased risk to develop squamous cell carcinoma (Indian J Lepr 1998;70:179)
Diagnosis is by PCR; most skin lesions have no identifiable bacteria (J Lab Physicians 2011;3:21)
Mitsuda reaction: intradermal injection of an armadilloderived lepra bacilli, is useful for classification
Description:
- Tuberculoid leprosy has hypopigmented center and raised erythematous border
- Lepromatous leprosy has macules, papules and plaques, but firm nodules may also be seen in the face
- Borderline leprosy has hypopigmented macules

Diagnosis

16S ribosomal RNA gene PCR assay (can use paraffin block)

Case reports

59 year old white man born in the United States with an extensive travel history presenting with progressive skin lesions, prior peripheral neuropathy and arthritis due to M. lepromatosis (CDC: Mycobacterium lepromatosis Lepromatous Leprosy in US Citizen Who Traveled to Disease-Endemic Areas [Accessed 26 November 2018])

Treatment

Clarithromycin, rifampin and dapsone

Microscopic (histologic) description

Tuberculoid leprosy: epithelioid histiocytes surround small cutaneous nerves; Langhans giant cells may be seen but without necrosis; the infiltrate may involve the papillary dermis up to the epidermis; may destroy arrectores pilorum muscle; bacilli are usually scarce
Lepromatous leprosy: macrophages (Virchow cells, lepra) are found in poorly circumscribed masses in the dermis, with few / no lymphocytes; macrophages may be distended with large groups of leprosy bacilli (globi); bacteria are present in large numbers in cutaneous nerves and in endothelium and media of small and large vessels; may invade arrectores pilorum muscle; may have subcutaneous nodules (erythema nodosum leprorum)
Borderline leprosy: perineural fibrosis with lamellar or onion skin pattern; more circumscription of the granulomatous response, more lymphocytes and closer relationship to nerves
Indeterminate leprosy: scanty superficial and deep lymphohistiocytic infiltrate in the dermis with some tendency to localize around appendages; increased mast cells
Histiocytoid leprosy: spindle cell proliferation with storiform pattern suggestive of fibrous histiocytoma
Lucio phenomenon: leukocytoclastic vasculitis and epidermal infarction

Microscopic (histologic) images

Contributed by Mowafak Hamodat, M.Sc.