DERM DILEMMA by MAURINE E . LESTER , CDT ; CHRISTOPHER SCHACH , MD ; ERIC STEWART , MD
A 61-year-old male veterinarian presents with a 2-3-month history of an enlarging well-demarcated plaque with scale , crusting , and oozing over his left second metacarpophalangeal joint . The lesion developed after an abrasion . The patient is currently taking oral trimethoprim-sulfamethoxazole and applying topical mupirocin with minimal response . The plaque has continued to increase in size and tenderness . The patient denies fever , cough , and chest pain .
Provided the clinical image and patient history , what is the most appropriate next step in the diagnosis and treatment of this patient ?
A .) Immediate biopsy to confirm the diagnosis of squamous cell carcinoma . Pending pathology results , the lesion should be excised utilizing a standard excision or Mohs surgery . Electrodessication and curettage is not recommended for this location .
B .) The lesion is consistent with pyoderma gangrenosum . A skin prick test causing a papule , pustule or ulcer is helpful in diagnosis ( pathergy phenomenon ) in addition to the clinical appearance and pain associated with the lesion . Necrotic tissue should be gently debrided and a Class I topical corticosteroid should be prescribed . Resolution may take several months to a year .
C .) A potassium hydroxide mount ( KOH ) is needed to assess for the presence of broad-based budding spores which suggests the patient has an infection with Blastomycosis . Skin biopsy for fresh tissue culture and special stains is necessary to confirm the KOH findings . If patient has any respiratory symptoms , a chest x-ray should be obtained to ensure there is not active pulmonary infection .
D .) This eruption represents dermatomyositis . Subsequent laboratory evaluation should include muscle enzymes as well as appropriate autoantibodies . A skin biopsy of the lesion is also necessary and will show a mild interface dermatitis with increased
mucin . Prescribe an oral corticosteroid , such as prednisone , to slow down the progression of the disease . This disease state is photosensitive so warn the patient to avoid direct sunlight . Inform the patient that this disease is not curable and will most likely necessitate chronic management .
Answer : C
Blastomycosis is a fungal infection caused by Blastomyces dermatitidis . This dimorphic fungus is most commonly found in the soil in North America , most notably the southeastern states , and is usually contracted by inhalation of the microscopic fungal spores from the air . Due to the method of transmission , blastomycosis most often presents as a pulmonary infection but may occasionally manifest cutaneous symptoms . It is rare for blastomycosis to only occur as a primary cutaneous infection but is possible through direct inoculation . From the patient ’ s history , it is known the lesion began as an injury . Given that the patient is a veterinarian , it is plausible that an animal was the vector for infection in this case and , interestingly , dogs are the most common animal to be infected with blastomycosis .
Typically , cutaneous blastomycosis presents as verrucous plaques and / or papulopustules with overlying erosions . Seropurulent scale / crust may occur around the periphery and the lesion ( s ) may ulcerate centrally . It is commons for skin lesions to occur on extremities , neck , and face and scarring is possible upon resolution . About half of patients with acute pulmonary blastomycosis will have flulike symptoms such as fatigue , muscle aches , chest pain , cough , and fever while others may be asymptomatic . Infected patients with compromised immune systems can experience more severe symptoms and are more likely to have the infection disseminate to other organs from the lungs . Symptoms of blastomycosis ( both cutaneous and pulmonary ) most often occur within a few weeks of inhalation or inoculation .
The key to diagnosing blastomycosis is observing broad-based budding spores from a KOH skin prep or biopsy specimen . The scraping and biopsy specimen were both positive for broad-based budding spores . Obtaining a deep tissue culture is ideal for confirming blastomycosis , but this specific fungal infection can be quite difficult to grow in a lab . In this case , it was not possible to do so . However , the clinical diagnosis in combination with the positive scraping and skin biopsy were enough to confirm the diagnosis . In some cases , blood or urine serologies may be used to aid the diagnosis . If blastomycosis manifests as a pulmonary infection , a chest X-ray or CT scan of the thorax can confirm the severity of the infection . In this particular patient ’ s case , a chest radiograph was not considered due to high suspicion of primary cutaneous disease and absence of pulmonary symptoms .
Treatment of blastomycosis is dependent upon extent and severity . In critical situations , Amphotericin B via intravenous administration is necessary . In most cases of cutaneous blastomycosis , orally administered azole antifungals are usually adequate . Oral Itraconazole 200mg twice daily was prescribed for this patient after assessment of hepatic transaminases . The necessary duration of treatment may vary from several months to a year . Itraconazole was discontinued after a total of seven months in this individual progress .
For a list of references , email ams @ arkmed . org .
124 • The Journal of the Arkansas Medical Society www . ArkMed . org