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BORRELIA INFECTIONS

Cat scratch disease

Etiology and pathogenesis

Cat scratch disease (CSD) is an infection acquired from cats and is caused by Bartonella henselae (formerly Rochalimaea henselae ). Patients are more likely (than a healthy cat owner) to have a kitten; to have been scratched, licked on the face, or bitten by a kitten; or to have a kitten with fleas.

Clinical

A scratch on the hand or arm by a cat, followed weeks later by painful lymphadenopathy that may suppurate, is characteristic (Fig.24.56). There may be a granulomatous nodule at the original scratch site. Rarely, secondary cutaneous lesions (e.g. erythema nodosum or erythema multiforme) or systemic involvement (e.g. of the liver, spleen, central nervous system, or bone) may occur. Encephalitis is rare, occurring in 1–7% of cases, and typically develops 2–6 weeks after the classic CSD pattern.

Figure 24.56 Cat scratch disease: papule at cat scratch. A scratch on the hand or arm by a cat, followed weeks later by painful lymphadenopathy that may suppurate is characteristic.

Differential diagnosis

The differential is that of isolated and sometimes suppurative lymphadenopathy; where there is a granulomatous inoculation site, then TB, other mycobacterial infection, and sporotrichosis may all need to be considered.

Treatment

Usually no treatment is needed in this self-limited condition. Ciprofloxacin (500mg twice a day), rifampin, and tetracycline have been reported to be helpful, although they do not seem to reliably shorten the course of the disease. Fluctuant nodules may be aspirated. There is no need to isolate. Tetracycline treatment of the cat has reduced B. henselae bacteremia, but the effect on recurrence of the disease in humans is unknown.

Erythema migrans

Etiology and pathogenesis

Erythema migrans is a cutaneous infection by one of three closely related species of Borrelia : B. burgdorferi , B. garinii , or B. afzelii . The vector is the nymph and adult female Ixodes (hard) tick. In the north-eastern and north-central regions of the USA , the principal vector is Ixodes scapularis (black-legged tick), and in the Pacific coast states, Ixodes pacificus (western black-legged tick) (Fig.24.57). It appears that the tick must be attached for at least 24–48 h to infect. Recently, the Lone Star tick ( Amblyomma americanum ) has been identified as being able to transmit erythema migrans. In the USA , states considered endemic regions are Connecticut , Rhode Island , New York , New Jersey , Pennsylvania , Maryland , Wisconsin , and Minnesota . This infection was previously termed erythema chronicum migrans, but lesions are not necessarily chronic and this part of the name has been dropped.

Figure 24.57 Tick bite by Ixodes pacificus. The vector for Lyme disease is the Ixodes tick. It appears that the tick must be attached for at least 24–48 h to infect.

Clinical

A red papule or macule that rapidly enlarges to form an annular lesion within a month of, and at the site of, a tick bite is characteristic of erythema migrans (Fig.24.58). The annulus is approximately 1–3cm in width, and the central area tends to clear. The primary lesion may alternatively be an urticarial plaque without central clearing, or may have a central dusky purpuric or necrotic appearance. Rarely, erythema migrans may be vesicular. Secondary annular lesions may occur through hematogenous spread. Fatigue, fever, arthralgias, and headache may accompany or precede the rash. Within the next few months, a small percentage of patients may develop neurologic (meningitis, neuropathy, or Bell palsy), cardiac (e.g. complete heart block), or musculoskeletal (e.g. chronic arthritis) changes. Obtaining an electrocardiogram may be appropriate.

    The diagnosis remains clinical. Confirmation may be attempted by skin biopsy with Warthin–Starry silver stain, culture of the organism from the skin, or serologic tests showing a high or rising titer (but both false positive and false negative results occur). The use of PCR of blood to detect the spirochete has been documented; it was positive in early Lyme disease 18.4% of the time in one study, and it was more likely to be positive if the patient had disseminated disease, fever, arthralgias, myalgias, or headache.

Figure 24.58 (a–c) Erythema migrans. The causative organism is Borrelia burgdorferi. (Panel c courtesy of Daniel K. Fram, M.D.)

Differential diagnosis

A hypersensitivity bite reaction can appear similarly. Bacterial cellulitis and its differential (Table 24.3) should always be considered.

Treatment

Adults and children over 8 years of age may receive a 21-day supply of doxycycline (100mg twice daily), amoxicillin (500mg three times a day), or cefuroxime axetil (500mg twice a day). The prognosis is good using any of these therapies. Minocycline (100mg twice a day) also appears effective. Methods that help prevent Lyme disease include avoiding endemic, wooded areas; applying insect repellent; wearing long pants and long-sleeved shirts; tucking pants into socks; plus checking regularly for ticks and, if found, removing them promptly.

Acrodermatitis chronica atrophicans

Etiology and pathogenesis

Acrodermatitis chronica atrophicans (ACA) is a late manifestation of Lyme borreliosis, and is characterized by initial inflammation of the skin followed by atrophy. The etiologic agent is Borrelia burgdorferi . Subspecies include B. burgdorferi sensu stricto , B. garinii , and B. afzelii . It tends to be a form seen in Central Europe .

Clinical

Edema and a bluish red discoloration develop first in ACA, which characteristically affects the extensor surface of the extremities. Atrophy and wrinkling then follow. Fibroid nodules may develop about the joints, and indurated skin lesions may occur, which can limit joint mobility. Peripheral and cranial nerves may be affected. Many patients complain of dysesthesias, cramps, and pain secondary to a peripheral neuropathy in the affected limb. Patients may remember experiencing a tick bite, erythema chronicum migrans, or both in the same general area 6 months to 13 years previously. Other manifestations of Lyme borreliosis (e.g. meningopolyneuritis, arthritis, and carditis) are usually not present.

    The clinical diagnosis is supported by a positive IgG titer against B. burgdorferi , but in Europe , 3–40% of the general population is positive for this antibody. Clinical suspicion may be confirmed by PCR detection of B. burgdorferi -specific DNA in lesional skin.

Differential diagnosis

In the inflammatory stage, there is a potentially wide differential, including disorders such as infective cellulitis and Wells' syndrome. Nodules, especially if there is arthritis, may be confused with rheumatoid nodules. The atrophic component, if it involves the dorsum of the hands in older patients, may suggest solar aging changes.

Treatment

The best treatment has not been determined. Doxycycline, amoxicillin, cefuroxime, or other appropriate antibiotics for Borrelia should be tried for 3 weeks or more. Intravenous ceftriaxone once daily for 2 weeks has been used. Resolution of the fibroid nodules followed by the bluish red discoloration of the skin are therapeutic end points. Once atrophy has developed, there is usually little response to treatment. The Jarisch–Herxheimer reaction may occur during treatment.

White/Cox: Diseases of the Skin, 2ed.(c) 2006, Elsevier Inc. All rights reserved.