CHAPTER 16
CUTANEOUS MYCOBACTERIUM INFECTIONS
（皮膚抗酸菌感染症）
I. Cutaneous Tuberculosis（皮膚結核）
A. Definition
Cutaneous tuberculosis (CTb) is highly variable in its clinical presentation, dependent on the immunologic status of the patient and the route of inoculation of mycobacteria into the skin.
B. Classification
1. Exogenous Infection
a. Primary inoculation tuberculosis (PITb)（皮膚初感染微候）
Via percutaneous inoculaton, in a nonimmune host
b. Tuberculosis verrucosa cutis (TbVC)（皮膚疣状結核）
Via percutaneous inoculation, in an individual with prior tuberculosis infection
2. Endogenous Spread
a. Lupus vulgaris (LV)（尋常性狼瘡）
b. Scrofuloderma (SD)（皮膚腺病）
c. Metastatic tuberculosis abscess (MTbA)（転移性結核膿瘍）
d. Acute miliary tuberculosis (AMTb)（急性栗粒性結核）
e. Orficial tuberculosis (OTb)（粘膜皮膚移行部結核）
f. Tuberculosis due to BCG lmmunization
C. Epidemiology and Etiology
1. Age
a. AMTb were common in infants and in adults with advanced immunodeficiency.
b. Pltb, in infants. SD, in adolescents, LV, all age
2. Sex
a. LV more common in females
b. TbVC more common in males
3. Occupation
TbVC : in physicians, medical students and pathologists, and in butchers and farmers from M. bovis.
4. Etiology
The obligate human pathogenic mycobacteria; M.tuberculosis, M.bovis, and occasionally bacillus Calmette-Gverin (BCG)
5. Incidence
CTb has steadily declined worldwide, paralleling the decline of pulmonary tuberculosis, However the incidence of CTb has been increasing, often associated with AIDS.
D. Tuberculosis Verrucosa Cutis (TbVC)（皮膚疣状結核）
1. Type
a. Initial papule with violaceous halo, then evolve to hyperkeratotic, warty, firm plaque.
b. Cleft and fissures occur from which pus and keratinous material can be expressed. Border often irregular.
c. No lymphadenopathy.
2. Color
Base brownish-red to purplish.
3. Distribution
Commonly on groin, dorsolateral hands and fingers.
E. Lupus Vulgaris (LV)（尋常性狼瘡）
1. Type
a. Initial flat papule is ill-defined and soft and evolves into well-defined, irregular plaque. Surface is initially smooth but may become hyperkeratotic. Hypertrophic forms result in soft tumorous nodules. Ulceration may occur.
b. Involvement of underlying cartilage (ears, nose) but not bone results in its destruction.
c. Scarring is prominent and new brownish infiltrates occur within the atrophic scar.
d. Occasionally, squamous cell carcinoma may arise from the scar.
2. Color
Reddish brown. Diascopy reveals an "apple-jelly" (i.e, yellowish-brown) color of the infiltrate.
3. Distribution
Usually solitary but several sites may occur. Most lesion on the head and neck, most often on nose and ears or scalp.
F. Scrofuloderma (SD)（皮膚腺病）
1. Type
a. Firm subcutaneous nodule which initially is freely movable; the lesion then becomes doughy and evolves into an irregular, deep-seated plaque which liquefies and perforates.
b. Ulcers and irregular sinuses discharge pus or caseous material, and edges are undermined, inverted, and dissecting subctaneuous pockets alternate with soft fluctuating infiltrates and bridging scars.
3. Color
Reddish blue, brownish.
4. Distribution
Most often in the parotidal, submandibular,supraclavicular, or axillary regions.
S.D most often results from affected lymph nodes or tuberculous bones (phalanges, sternum, ribs) or joints.
5. Dermatopathology
a. PITb: initially non-specific inflammation, after 3 to 6 weeks, epitheloid cells, Langhans giant cells, lymphocytes and caseation necrosis; i.e. tuberculoid structure.
b. AMTb: nonspecific inflammation and vasculitis.
c. All other forms of CTb: typical tuberculous histopathology.
d. Mycobacteria are found in the lesional tissue.
6. Treatment
Prolonged antituberculous therapy with at least two drugs is indicated for all cases of cutaneous tuberculosis.
II. Cutaneous Atypical Mycobacterium Infection（皮膚非定型抗酸菌症）
A. Definition
Mycobacteria other than Mycobacterium tuberculosis are environmental mycobacteria,
commonly found in water and soil, have low-grade pathogenicity, and are never
transmitted person-to-person.
B. Synonyms
swimming pool granuloma, fish tank granuloma
C. Etiology
Mycobacterium marinum, most commonly
Mycobacterium avium infection increasing
D. Transmission
Mycobacterium marinum : Traumatic inoculation into skin during aquatic activity.
Mycobacterium avium: contamination of 24-hour hot bathtub
E. Season
1. Swimming pool granuloma: In summertime.
2. Fish tank granuloma: No seasonal variation.
F. History
1. Inoculation Period: Few weeks to few months following inoculation.
2. Duration of Lesions: Months to years.
3. Onset and Symptoms:
Lesion at site of injury while in aqueous environment, i.e., hands and fingers.
Asymptomatic, but local tenderness or painful when bumped.
G. Skin Lesions
1. Type of lesion
At site of inoculation, papules enlarging to inflammatory nodule or plaque 1.0 to 4.0 cm with scales, crust or ulcer. At the site of spontaneous regression, atrophic scarring follows.
2. Sporotrichoid Pattern
a. deep-seated subcutaneous nodules (1.0 to 2.0 cm) spread in linear confiquration proximal to the original lesions on the hands or forearm.
b. disseminated Cutaneous Infection: distinctly rare
H. Distribution
1. Following trauma while swimming: on elbow, finger, knee
2. Following aquarium exposure: commonly of right hand
I. General Examination
Regional lymphadenopathy and lymphangitis
J. Diagnosis
Confirmed by isolating Mycobactera (M, marium, M, fortuitam, M, kansasil, M. avium…etc.) by culture of lesional fissure or exudate.
K. Skin Test
PPD often positive
L. Skin Biopsy
Suggestive but not pathognomoric
1. Early: dermal inflammatory reaction with lymphocytes, polymorphonuclear cells, histiocytes.
2. Older lesion: tuberculoid architecture is developed with epitheloid cells and Langhans' giant cells:
3. No typical caseation necrosis.
4. In biopsy tissue, acid-fast bacillus are infrequent.
M. Course and Prognosis
Most usually benign and self limited but can remain active for a prolonged period (months to 3 years)
N. Treatment
a) Initially, minocycline. Once M. marinum has been isolated, sensitivity studies should be performed. In sporotrichoid form rifampin-ethanbutol should be given.
b) Surgical excision