Derm Dx: Bright plaques, papules on the thumb - Clinical Advisor

Derm Dx: Bright plaques, papules on the thumb

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A patient, aged 34 years, presented for evaluation of a rash on his dorsal proximal right thumb and right wrist. The rash was first noted three weeks ago on the thumb. The patient applied clobetasol spray, but the rash became more red and diffuse.

Upon further questioning, the patient revealed that he was a salesman who enjoyed gardening in his free time.

Physical examination revealed bright erythematous plaques and papules of the right thumb and wrist. The patient was afebrile and his axillary lymph nodes were non palpable.

A culture was obtained and the patient was started on itraconazole pending culture. When the patient was seen 10 days later, the erythema and the elevation of the plaque and papules had diminished.

Based on the clinical appearance and patient history, the presumptive diagnosis was sporotrichosis. Upon further questioning the patient recalled a rose thorn penetration at the initial site when gardening. The culture results confirmed sporotrichosis. Cutaneous sporotrichosis is an infection caused...

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Based on the clinical appearance and patient history, the presumptive diagnosis was sporotrichosis. Upon further questioning the patient recalled a rose thorn penetration at the initial site when gardening. The culture results confirmed sporotrichosis.

Cutaneous sporotrichosis is an infection caused by the fungal organism Sporothrix schenckii. This infection usually results from direct fungal inoculation through trauma with a thorn or splinter but zoonotic cases do occur from a bite or a scratch of cats, dogs, rodents, parrots, horses, or armadillos.1,2

The fungus is predominantly found on decaying vegetation, soil, thorns, animal claws, and sphagnum moss. Consequently, patients with a higher risk of sporotrichosis are gardeners, florists, veterinarians, and farmers due to higher exposure to plants, soil, and animals.3

Sporotrichosis first manifests with symptoms approximately 3 weeks after onset of infection. Classic disease is characterized by initial symptoms of small, painless erythematous papules at the site of inoculation, commonly on the arm or hand.1

The organism will then spread through the lymphatic system, forming papules and nodules along the lymphatic tracts. The lesions will then undergo necrosis, forming ulcerations, crusting, or drainage.3

Disseminated cutaneous and extracutaneous types of sporotrichosis are rare and usually manifest in immunocompromised individuals.2,3,4 These result from hematogenous spread of the organism throughout the body, and may eventuate in stiffness and pain in the large joints, brain abscesses, meningitis, or pulmonary disease.2

The gold standard for diagnosis of sporotrichosis is culture. Sporotrix schenckii has a dimorphic quality that exists as a mold at 25oC and a yeast at 37oC.3,4 A positive culture on Sabouraud dextrose agar will grow best at 25oC and will demonstrate white, smooth, or verrucous colonies with aerial mycelium that turn brown to black.3

Microscopy of the fungus is characterized by thin branching hyphae with conidia.3,4 A biopsy can be done, but may not be diagnostic due to the small number of organisms present.3 A biopsy of an initial lesion will show a non-specific inflammatory dermal infiltrate with epidermal changes, such as hyperplasia and hyperkeratosis. A biopsy at 28 days after infection often demonstrates granulomas comprised of lymphocytes and lesser amounts of neutrophils and fungal organisms.1

The drug of choice for cutaneous and lymphocutaneous sporotrichosis is itraconazole.5,6 Alternatively, fluconazole can be used if itraconazole is untolerable, but it is less effective.5 Potassium iodide was the drug of choice before the advent of azoles and is still considered a viable treatment option.6

In rare cases, such as pregnancy, daily treatments with local hyperthermia using a device that generates heat at 42 to 43oC has proven efficacy.5

Sporotrichosis is a treatable cutaneous infection that can be diagnosed early given clinical suspicion and proper history. Clinicians should consider this infection in their differential when patients present with papules on the hands or arms with a history of outdoor exposure, especially gardening. 

Megha D. Patel, is a student at the Commonwealth Medical College, Scranton, Pennsylvania.

Stephen Schleicher, MD, is an associate professor of Medicine at the Commonwealth Medical College and an Adjunct Assistant Professor of Dermatology at the University of Pennsylvania Medical College. He practices dermatology in Hazleton, Pennsylvania.

References

  1. Fernandex-Flores A, Saeb-Lima M, Arenas-Guzman R. Am J Dermatopathol. 2014; 36(7): 531-553.
  2. Morris-Jones R. Sporotrichosis. Clinical and Experimental Dermatology. 2002; 27:427-431.
  3. Trent J, Kirsner R. Adv Skin Wound Care. 2003; 16:122-129.
  4. Mahajan VK, Sharma NL, Shanker V, Gupta P, Mardi K. Indian J Dermatol Venerol Leprol. 2010; doi: 10.4103/0378-6323.62974.
  5. Kauffman CA, Hajjeh R, Chapman SW. Clinical Infectious Disease. 2000; 30: 684-687.
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