Skin nontumor

Infectious disorders


Editor-in-Chief: Debra L. Zynger, M.D.
Priya Nagarajan, M.D., Ph.D.

Last author update: 13 September 2019
Last staff update: 30 June 2023

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PubMed Search: Coccidioidomycosis[title] skin

See also: lung, lymph nodes

Priya Nagarajan, M.D., Ph.D.
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Cite this page: Wang J, Nagarajan P. Coccidioidomycosis. website. Accessed September 21st, 2023.
Definition / general
Essential features
ICD coding
  • ICD-10: B38.9 - coccidioidomycosis, unspecified
  • Major systemic mycosis
  • Relatively more common in Mexico, Central and South America (J Am Acad Dermatol 2006;55:929)
  • Endemic in the U.S. southwestern deserts
  • Most important risk factor is dust exposure in endemic areas
  • Coccidioides species exist in two phases (J Am Acad Dermatol 2006;55:929)
    • Mycelial phase
    • Spherule phase
  • Mycelia are found in the soil and made of septate and ramified hyphae; as the environment dries, mycelia reproduce thick walled spores named arthroconidia
  • Infection occurs with inhalation or rare inoculation of arthroconidia
  • Within the host, spherules are preferentially produced, which then develop internal endospores; the endospores are released and spread to nearby or distant tissues
  • May be classified into primary and secondary disease; 40% of patients present with primary disease which generally affects the lungs
  • Primary involvement of the skin is quite uncommon; acquired by direct inoculation of the fungus by means of splinters and abrasions
  • 5 - 10% of cases present with secondary disease which can affect the lungs and become a chronic process
  • Disseminated disease commonly involves the skin, bones, joints, nervous system pericardium, peritoneum, skeletal muscle and meninges
  • Caused by the dimorphic, soil borne ascomycete fungi Coccidioides immitis (typically in California) and Coccidioides posadasii (typically outside of California); clinical differences between the two species have not been observed (J Am Acad Dermatol 2006;55:929)
Clinical features
  • Cutaneous manifestations are categorized as reactive and organism specific (J Am Acad Dermatol 2006;55:929)
  • Reactive manifestations do not contain visible microorganisms and may exhibit features of erythema nodosum, Sweet syndrome and interstitial granulomatous dermatitis
  • Rarely, patients may exhibit features of erythema multiforme, acute generalized exanthema, secondary to hypersensitivity to systemic infection
  • Organism specific manifestations present with lesions that contain the organism and include secondary cutaneous disease or primary cutaneous disease
  • Secondary cutaneous disease occurs in patients with disseminated disease
  • Clinical appearance is heterogeneous, including papules, nodules, gummas, pustular acneiform lesions, ulcerated and verrucous plaques, scars, abscesses and fistulae (Am J Dermatopathol 2018;40:e41)
  • Primary cutaneous infection results from direct traumatic inoculation of the organism into the skin by an external source and typically manifests as a painless, indurated or verrucous nodule with or without ulceration, typically on an extremity
  • Secondary nodules may arise in a linear lymphatic sporotrichoid distribution (Clin Exp Dermatol 2010;35:e42)
Prognostic factors
  • Immunosuppression is a poor prognostic factor
Case reports
Clinical images

Images hosted on other servers:

Facial infection

Ulcerated should lesion

Red plaque on finger

Disseminated disease

Microscopic (histologic) description
  • Primary cutaneous lesions are typically characterized by coexistence of pseudoepitheliomatous hyperplasia of epidermis and adjacent or admixed acute suppurative inflammation (Am J Dermatopathol 2014;36:531, J Am Acad Dermatol 2006;55:929, Am J Dermatopathol 2018;40:e41)
  • Variable infiltrate of neutrophils, eosinophils, histiocytes, multinucleated giant cells, plasma cells and rarely lymphocytes are present
  • Organisms are typically rare and may require multiple sections to identify
    • Measure up to 100 μm in diameter, with an eosinophilic wall, containing multiple basophilic or pale endospores (up to 5 μm)
  • Spherules are usually present in association with histiocytic neutrophilic infiltrate or rarely within the hyperplastic squamous epithelium
  • Budding is extremely rare
Microscopic (histologic) images

Contributed by Priya Nagarajan, M.D., Ph.D.

Epidermal hyperplasia, inflammation

Large yeast forms

PAS positive yeasts

Positive stains
Negative stains
Sample pathology report
  • Left lower leg, skin shave biopsy:
    • Rare large yeast forms with broad based budding, in association with epidermal hyperplasia and acute inflammation, consistent with cutaneous coccidioidomycosis
Differential diagnosis
Board review style question #1
Which of the following histologic features is typical of cutaneous coccidiodomycosis>

  1. Irregular epidermal hyperplasia, mixed inflammatory infiltrate and rare large spherical fungal forms with eosinophilic wall and pale center
  2. Lobulated, endophytic epidermal hyperplasia, with large pink intracytoplasmic inclusions that compress the nucleus against the cell membrane
  3. Multinucleated histiocytes with angulated nuclei that fit against each other and basophilic chromatin that marginates against the nuclear membrane
  4. Subcorneal cleft with scant inflammatory infiltrate and variable acantholysis
Board review style answer #1
A. Irregular epidermal hyperplasia, mixed inflammatory infiltrate and rare large spherical fungal forms with eosinophilic wall and pale center. B, C and D are characteristic histologic features of molluscum, herpes and staphylococcal scalded skin syndrome.

Comment here

Reference: Coccidioidomycosis
Board review style question #2
Which of the following is the most common primary site of infection in coccidioidomycosis?

  1. Brain
  2. Lung
  3. Mucocutaneous junction
  4. Skin
Board review style answer #2
B. Lung

Comment here

Reference: Coccidioidomycosis
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