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Are You Confident of the Diagnosis?
What you should be alert for in the history
Pseudomonas hot-foot syndrome, a primary skin infection caused by the bacteria Pseudomonas aeruginosa, was first recognized as a distinct entity in 2001. Emersion of the feet in contaminated water causes the sudden onset of painful plantar nodules, 6 to 48 hours after exposure. Pain is the first symptom and is often so extreme that the patient may be unable to wear socks or shoes.
Characteristic findings on physical examination
Physical findings are characterized by diffuse plantar erythema with 1-2cm painful, deep red to violaceous nodules, predominately on weight-bearing areas. These painful nodules have less commonly been reported on the palms. Lymphadenopathy is typically absent.
Expected results of diagnostic studies
Serologic studies may reveal a leukocytosis, neutrophilia, elevated erythrocyte sedimentation rate, and elevated C-reactive protein. If a deep pustule is present, it can be cultured to grow P. aeruginosa – the same strain can also be cultured from the contaminated water. Histologic examination shows a dense perivascular, periadnexal, interstitial, and perieccrine neutrophilic infiltrate extending into the subcutaneous fat.
Diagnosis confirmation
There is a narrow differential diagnosis.
Idiopathic palmoplantar hidradenitis/neutrophilic eccrine hidradenitis presents in a manner similar to pseudomonas hot-foot syndrome. It also demonstrates a perieccrine neutrophilic infiltrate on biopsy, which is indistinguishable on H&E staining. Tissue gram stain may be used to look for gram negative rods in Pseudomonas hot-foot syndrome. Tissue culture can be very helpful in differentiating the two.
Many idiopathic palmoplantar hidradenitis cases are caused by medications (especially chemotherapeutics). Idiopathic palmoplantar hidradenitis is also sporadic and without any associated exposure to contaminated water.
Pressure urticaria also presents as tender macules and papules on weight-bearing areas of the feet, but it is associated with prolonged mechanical stress to the areas. Aquagenic urticaria may also be a consideration in the differential diagnosis. Hives typically occur in the areas of water exposure and are rarely if ever isolated to the palms and soles. Urticarial reactions also tend to be pruritic and not tender. The individual hives resolve within 24 hours.
Suppurative panniculitis due to Pseudomonas presents with painful nodules on the legs, spares the soles, and is sporadic in nature. This condition has a higher incidence of bacteremia/sepsis and typically requires incision, drainage, and antibiotics for resolution.
Erythema nodosum is a septal panniculitis with painful nodules on the anterior lower legs, not the soles.
Symmetric lividities (symmetric lividity) of the soles was most commonly reported during World War II as symmetrical, moist hyperkeratotic plaques of the soles with surrounding, well-demarcated erythema. The areas are tender when walking and have characteristically pronounced hyperhidrosis and bromhidrosis.
Who is at Risk for Developing this Disease?
Pseudomonas hot-foot syndrome is most commonly seen in children due to their thin stratum corneum, allowing for easier penetration of the bacteria. Any other interruption to the integrity of the epidermis (including abrasion from hot tub/pool/spa floors or microtrauma from walking on the ground with bare feet) will also put an individual at risk for infection following contaminated water exposure. P. aeruginosa flourishes best in warm water with a low chlorine level and high pH, making poorly treated hot tubs and pools the most common sources of infection.
What is the Cause of the Disease?
P. aeruginosa is an aerobic or facultative anaerobic, opportunistic, gram-negative rod ubiquitously found in soil and water. The stratum corneum serves as a physical, primary defense to infection. Any hyperhydration (occlusion, sweating, maceration) or destruction (microtrauma, dermatitis) of the epidermis interrupts the physical barrier and may lead to colonization and proliferation of P. aeruginosa. Collagenase, elastase, phospholipase, heat-stable thermolysin, vascular permeability factor, and fibrolysin are all produced by P. aeruginosa and facilitate spread of infection after invasion of the epidermis. This bacteria is capable of producing various pigments including pyocyanin, pyoveridine, and pyorubin.
Systemic Implications and Complications
Pseudomonas hot-foot syndrome may cause low-grade fever, malaise, and nausea in the most severe of cases. Other systemic complications have not been reported and the condition typically self-resolves, without any sequelae, in less than 14 days.
Treatment Options
Treatment options are summarized in Table I.
Table I.
| Medical | Surgical | Physical Modalities |
| Supportive therapies (analgesics such as acetominophen) | Incision and drainage (rarely required). Incision and drainage (I&D) of pustule for culture purposes | Elevate legs |
| Antibiotics – only needed for severe cases | Cool compresses |
Optimal Therapeutic Approach for this Disease
Avoid the source of infection (pool/hot tub/spa). Decontaminate the source (see Hot tub folliculitis chapter). Report outbreaks to the local health authorities.
Culture any pustules or purulence if present. Check for fever. If any fever or constitutional symptoms are present check a complete blood count (CBC) with differential count. Consider an infectious diseases consult.
Pseudomonas hot-foot syndrome is a self-limiting condition (resolving in 14 days) and as such, observation alone is acceptable. Pain is the most common symptom and cold compresses, leg elevation, and analgesics (acetaminophen) are helpful as supportive care.
Antibiotics are typically not needed. In cases of immunosuppression (HIV, organ transplant, chronic immunosuppressant medications) the use of antibiotics is likely indicated (there have not been any cases reported in this population to date). Treat with intravenous or intramuscular ceftazidime in children or oral ciprofloxacin 750mg orally twice daily for 5-7 days in adults.
Treating complicated immunosuppressed children and adults with hot-foot syndrome should prompt one to get a pediatric or an adult infectious diseases consult for advice. The use of ciprofloxacin in children was reported in a case series in which a 4-year old and 9-year old were successfully treated with ciprofloxacin.
Antibiotics may shorten the duration of disease, with one report of nodules clearing after 2 days of treatment. Antibiotic therapy may be targeted if a culture and sensitivities are available or empiric with an antipseudomonal cephalosporin (ie, ceftazidime) or a fluoroquinolone in adults. Treatment length is typically 5-7 days. Fluoroquinolone use in children has been associated with permanent bone and cartilage damage.
No controlled studies have been performed to determine the best therapy. Therapy should be based on the clinical signs and symptoms of the patient.
Patient Management
Patients and their parents should be informed of the self-limiting nature of pseudomonas hot-foot syndrome and its likelihood to reoccur with re-exposure to the contaminated water. Recall of the exposure source is important in order to notify other individuals who may be affected. Suspected water may also be tested for P. aeruginosa; its treatment may be adjusted to obtain an optimal pH and chlorine level. Prevention may be achieved with the use of rubber pool shoes.
Unusual Clinical Scenarios to Consider in Patient Management
Most cases involve only the soles. The palms are much less likely to be affected, and the minority of cases affect both the palms and soles. The syndrome has been seen in conjunction with hot tub folliculitis.
What is the Evidence?
Fiorillo, L, Zucker, M, Sawye, D, Lin, AN. “The pseudomonas hot-foot syndrome”. N Engl Med. vol. 345. 2001. pp. 335-8. (The first report of pseudomonas hot-foot syndrome recognized as an outbreak from a community wading pool affecting 40 patients who ranged in age from 2-15 years of age. All had the symptoms occur within 40 hours of exposure to the same contaminated swimming pool (swimming pool culture was performed and found to be contaminated with the same strain of P. aeruginosa as was found on one of the children). All cases resolved in 14 days. Three cases recurred after reexposure to the contaminated pool.)
Yu, Y, Cheng, AS, Wang, L, Dunne, WM, Bayliss, SJ. “Hot tub folliculitis or hot hand-foot syndrome caused by pseudomonas aeruginosa”. J Am Acad Dermatol. vol. 57. 2007 Oct. pp. 596-600. (Two case reports of pseudomonas hot-foot syndrome with similar palmar findings. These two cases were found to be a subset of 33 patients that developed pseudomonas folliculitis or hot-foot syndrome. All the children had been exposed to the same pool/hot tub. These two cases were more severe with leukocytosis and consitutional symptoms. After the diagnosis was made both these children were treated successfully with oral ciprofloxacin.)
Silvestre, JF, Betlloch, MI. “Cutaneous manifestations due to pseudomonas infection”. Int J Dermatol. vol. 38. 1999. pp. 419-31. (A nice review of Pseudomonas infections, including microbiology, epidemiology, and pathogenesis.)
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