1. What essential question remains to be asked in order to make the diagnosis?
2. What is the tentative diagnosis?
3. Can you list at least three differential diagnoses?
4. What features of this condition separate it from other conditions in the differential diagnosis?
5. What is the suitable treatment of this rash?
When A Patient Presents With A Lower Extremity Rash
Podiatric physicians are often presented with dilemmas when diagnosing various dermatological conditions as these conditions may have overlapping symptoms. An accurate diagnosis is dependent on the patient history, physical examination and asking key questions to elicit telling answers from the patient. Accordingly, we have launched a new bimonthly column, “Dermatology Diagnosis,” that will test one’s skills in diagnosing dermatological conditions. Without further delay, let us consider the first case. A 26-year-old male presents with a four-day history of red, itchy bumps on his lower legs. He says he woke up four days before with itching on both lower legs and noticed small red bumps beginning below both of his knees and progressing down toward his feet. After approximately 24 hours, the patient noticed that the condition started to itch more and appeared to get worse. During the history portion of the visit, the patient says he had no idea how the rash started and had no previous history of a similar rash anywhere on his body. He reported that he was otherwise in good health but recently had systemic symptoms of fatigue, joint pain, muscle aches and a mild headache, which he first noted two days after the rash appeared. The patient has no history of allergy to any medications, foods or other substances, and is not taking any medications or vitamins at this time. Furthermore, the patient maintains he had not started to use any new cleaning products, bath soaps, laundry detergents or topical preparations of any kind prior to this problem. He has not gone camping or hiking in the past month, and has not gone out of the state in the last two months. The patient says he checked his bed carefully for any bugs and found none. None of his roommates has a similar problem.
What Did The Examination Reveal?
The physical examination shows an array of small (3 to 8 mm) erythematous, pruritic, follicular papular eruptions, many with apparent pustules, confined to the lower legs. There are a few small areas of urticaria and a few small nodular lesions on the legs. There are no lesions on the hands, arms or feet. Upon careful questioning of the patient, he reveals that he has a few similar lesions around the groin area. Some of the larger lesions are tender to direct palpation. There is no increase in skin temperature and no edema. The remaining examination is negative for elevated oral temperature or other signs or symptoms. There are no other obvious dermatological findings other than those noted from the initial examination.
Inside Insights On Hot Tub Dermatitis
The most common misdiagnosis is that of insect bites. In this case, the patient has Pseudomonas folliculitis, which is also called “hot tub dermatitis.” He had been in his friend’s hot tub on two occasions just before the pruritic rash broke out. In this case of Pseudomonas folliculitis, perifollicular pustules began appearing one to two days after exposure to a contaminated hot tub. Although “hot tub” folliculitis is usually caused by Pseudomonas aeruginosa, one does not need to obtain a culture to establish this diagnosis. This can be a difficult diagnosis to make unless you recognize the pattern and ask the essential question about hot tub exposure. Other sources of this infection include contaminated whirlpools and spas. Folliculitis can also be caused by other bacterial organisms such as Staphylococcus aureus and Streptococcus pyogenes. Clinicians may take a specimen from some pustules for bacterial culture if there is uncertainty about the causative agent. Pseudomonal folliculitis presents as erythematous skin lesions any time from eight hours to five days or more (the mean incubation period is 48 hours) after using a contaminated hot tub, water slide, physiotherapy whirlpool or contaminated loofah sponge. Malaise and fatigue may occur during initial days of the eruption. Fever is uncommon and it is low grade when present. Pseudomonal folliculitis may present with just a few to dozens of small (0.5 to 3 cm) spherical urticarial plaques, with a central papule or pustule on all skin surfaces exposed to long-term soaking in contaminated water. Typically, this condition occurs on the legs, groin area, waist, under the breast in females and on the back area. The lesions are usually concentrated in areas covered by a bathing suit and usually spare the head, neck and hands. The rash can be a polymorphous eruption or a mixture of follicular, maculopapular, vesicular or pustular lesions. These lesions are often extremely pruritic. Usually, no treatment is necessary as the folliculitis clears spontaneously in seven to 10 days. However, one can treat the intense itch with 25 to 50 mg of diphenhydramine hydrochloride at bedtime. Some patients may have recurrent crops of lesions over an extended period of up to three months, which may leave round spots of red-brown postinflammatory hyperpigmentation. For severely symptomatic patients or those who have re-exposure, one can use ciprofloxacin for five to seven days.
The differential diagnosis for a pruritic erythematous papular eruption is vast. Some of the more common possibilities include insect bites, viral exanthema, scabies, various fungal infections as well as allergic reactions to medication, foods, soaps, laundry detergents, topical preparations, plants or clothing. In this case, careful examination with a magnifying lens was necessary to determine that the lesions were observable around hair follicles and that some were pustular. This helped to make this diagnosis. The primary descriptive characteristics of Pseudomonas folliculitis include papules, pustules, urticarial plaques, macules and vesicles. Prevention requires meticulous cleaning of the hot tub and appropriate water chemical management. Dr. Dockery is a Fellow of the American College of Foot and Ankle Surgeons, and a Fellow of the American Society of Podiatric Dermatology. He is board certified in foot and ankle surgery. He is the Chairman of the Board and Director of Scientific Affairs for the Northwest Podiatric Foundation for Education and Research in Seattle. Dr. Dockery is the author of Cutaneous Disorders of the Lower Extremity (Saunders, 1997) and Lower Extremity Soft Tissue & Cutaneous Plastic Surgery (Elsevier Science, 2006). Editor’s note: For related articles, see “What You Should Know About Atopic Dermatitis” in the September 2005 issue of Podiatry Today. Also be sure to check out the archives at www.podiatrytoday.com.
Suggested Reading 1. Bottone EJ, Perez AA: Pseudomonas aeruginosa folliculitis acquired through use of a contaminated loofah sponge: an unrecognized potential public health problem. J Clin Microbiol.; 31(3):480-3, 1993.
2. Chen S, Rudoy R: Pseudomonas Infections. eMedicine, March 27, 2006. Available online: www.emedicine.com/ped/topic2701.htm
3. Krivda S, Toner CB: Pseudomonas folliculitis. eMedicine. May 17, 2006. Available online: www.emedicine.com/DERM/topic356.htm
4. Silverman AR, Nieland ML: Hot tub dermatitis: a familial outbreak of Pseudomonas folliculitis. J Am Acad Dermatol; 8(2):153-156, 1983.