Current epidemiology of tinea corporis and tinea cruris causative species: Analysis of data from a major commercial laboratory, United States

To the Editor:

Tinea corporis and cruris are common dermatophytoses receiving renewed attention given the emergence of severe, antifungal-resistant cases.^1,2 US data on causative species are outdated and geographically limited.³ Updated data could inform treatment guidelines and surveillance efforts. Therefore, we described fungal culture results from patients with suspected tinea corporis or cruris.

Using data from Labcorp, a major US commercial laboratory, we analyzed results from fungal cultures ordered March 1, 2019 to March 1, 2023 among patients whose reason for testing was tinea corporis or cruris. For each tinea type, we examined fungal culture results by patient demographic characteristics, ordering clinical specialty, and species.

In total, 15,563 and 2026 culture results were analyzed from patients with suspected tinea corporis and cruris, respectively (Table I). In the corporis group, median patient age was 30 years (interquartile range = 12–56); 51.4% were male. In the cruris group, median patient age was 46 years (interquartile range = 30–63); 76.8% were male. In both groups, most culture results were from South or Northeast residents and ordered by dermatologists.

Table I.

Fungal culture results from persons with suspected tinea corporis or tinea cruris, United States, March 1, 2019 to March 1, 2023^*

	Tinea corporis		Tinea cruris
Characteristic	N = 15,563	%	N = 2026	%
Age group, y
0–17	5644	36.6	221	11.1
18–44	4374	28.4	740	37.3
45–64	3053	19.8	611	30.8
≥65	2344	15.2	414	20.8
Unknown†	148	—	40	—
Sex
Male	7831	51.4	1521	76.8
Female	7412	48.6	459	23.2
Unknown†	320	—	46	—
US census region
South	6741	43.3	835	41.2
Northeast	6707	43.1	837	41.3
West	1124	7.2	257	12.7
Midwest	991	6.4	97	4.8
Physician type
Dermatology	9380	69.0	1293	71.6
Pediatrics	2362	17.4	90	5.0
FM, GP, or IM	1251	9.2	253	14.0
Other	601	4.4	170	9.4
Unknown†	1969	—	220	—
Fungal culture results
Negative/no fungal growth	12,053	77.4	1497	73.9
Positive for fungus	3510	22.6	529	26.1
Dermatophytes	1953	55.6	195	36.9
Trichophyton (species specified)‡	1486	76.1	165	84.6
T rubrum	599	40.3	128	77.6
T tonsurans	736	49.5	24	14.5
Other Trichophyton species	151	10.2	13	7.9
Unspecified Trichophyton species and other dermatophytes	467	23.9	30	15.4
Nondermatophyte molds	578	16.5	54	10.2
Dematiacious molds	318	55.0	26	48.1
Other	260	45.0	28	51.9
Yeasts§	710	20.2	232	43.9
Candida species	415	58.5	186	80.2
Unspecified yeast	96	13.5	23	9.9
Other	199	28.0	23	9.9
Unspecified fungus	269	7.7	48	9.1

FM, Family medicine; GP, general practitioner; IM, internal medicine.

^*Labcorp, a major US commercial laboratory, sends data to Centers for Disease Control and Prevention’s National Syndromic Surveillance Program (https://www.cdc.gov/nssp/index.html), which is a collaborative electronic health data sharing effort among Centers for Disease Control and Prevention, health departments, and academic and private sector partners. Logical Observation Identifiers Names Codes 17947–3, 17948–1, 17949–9, 18482–0, 42804–5, 42805–2, and 51723–5 were used to identify fungal culture results. The study period represents the widest range of available data at the time of analysis.

^†Excluded from the denominator for frequency calculations.

^‡Among all Trichophyton results identified to the species level, 5.5% were Trichophyton mentagrophytes; other uncommon (<5%) Trichophyton species identified were T soudanese, T violaceum, T interdigitale, and T verrucosum. Among all dermatophyte species, the most common non-Trichophyton genus was Microsporum.

^§Among Candida results from patients with suspected tinea corporis, the most frequent species were Candida parapsilosis (n = 183, 44.1%), Candida albicans (n = 152, 36.6%), and Candida lusitaniae (n = 14, 3.4%). Among Candida results from patients with suspected tinea cruris, the most frequent species were C albicans (n = 134, 72.0%) and C parapsilosis (n = 35, 18.8%). Among the “other” yeast results the most common results were species from the genera Rhodotorula (65.8%) and Malassezia (18.6%) for patients with suspected tinea corporis and Rhodotorula (65.2%) for patients with suspected tinea cruris.

Percent positivity was 22.6% (3510/15,563) in the corporis group and 26.1% (529/2026) in the cruris group, without substantial variation by demographic characteristics or ordering specialty (Table II). Among positive results, in the corporis group, most were dermatophytes (55.6%, 76.1% of which were Trichophyton with species-level identification, mostly Trichophyton tonsurans [49.5%] and Trichophyton rubrum [40.3%]), then yeasts (20.2%, 58.5% of which were Candida species), nondermatophyte molds (16.5%), and unspecified fungus (7.7%).

Table II.

Percent positivity among fungal culture results from persons with suspected tinea corporis or tinea cruris, United States, March 1, 2019 to March 1, 2023

Characteristic	Tinea corporis (N = 15,563)	Tinea cruris (N = 2026)
Age group, y
0–17	1413/5644 (25.0)	54/221 (24.4)
18–44	778/4374 (17.8)	178/740 (24.1)
45–64	667/3053 (21.8)	179/611 (29.3)
≥65	617/2344 (26.3)	109/414 (26.3)
Sex
Male	1904/7831 (24.3)	404/1521 (26.6)
Female	1541/7412 (20.8)	112/459 (24.4)
US census region
South	1728/6741 (25.6)	235/835 (28.1)
Northeast	1310/6707 (19.5)	200/837 (23.9)
West	257/1124 (22.9)	62/257 (24.1)
Midwest	215/991 (21.7)	32/97 (33.0)
Provider type
Dermatology	2044/9380 (21.8)	328/1293 (25.4)
Pediatrics	623/2362 (26.4)	20/90 (22.2)
FM/GP/IM	285/1251 (22.8)	71/253 (28.1)
Other	122/601 (20.3)	48/170 (28.2)
Total	3510/15,563 (22.6)	529/2026 (26.1)

FM, Family medicine; GP, general practitioner; IM, internal medicine.

In the cruris group, yeasts were most common (43.9%, 80.2% of which were Candida species), then dermatophytes (36.9%, 84.6% of which were Trichophyton with species-level identification, mostly T rubrum [77.6%] and Trichophyton tonsurans [14.5%]), nondermatophyte molds (10.2%), and unspecified fungus (9.1%). In both groups, Trichophyton soudanese, Trichophyton violaceum, Trichophyton interdigitale, and T verrucosum were identified, each composing <5% of Trichophyton with species-level identification.

This is the largest US study of tinea corporis and cruris culture results to date. Our low positivity rates (≤26.1%) were similar to a 1999 to 2002 U.S. study (26.3%) that included 505 body or groin site cultures.³ This might reflect the insensitivity of fungal cultures. Alternatively, some patients might have had nonfungal skin conditions (eg, psoriasis), reinforcing the importance of a broad differential and diagnostic testing (eg, potassium hydroxide preparation, polymerase chain reaction) given the inaccuracy of visual diagnosis.⁴ The previous study found T rubrum was the predominant dermatophyte³; however, that study aggregated body/groin results, making comparison difficult with our study, where T tonsurans predominated in the corporis group and T rubrum predominated in the cruris group. Yeasts were common among positive culture results, especially for the cruris group (43.9%), potentially representing colonization or infection. Trichophyton soudanense and T violaceum, species primarily associated with immigration in the United States from certain African countries,⁵ remain uncommon.

Study limitations include representativeness and lack of information on the emerging dermatophyte Trichophyton indotineae, whose differentiation from other Trichophyton species requires advanced molecular testing available only at select reference laboratories.²

This study updates tinea corporis and cruris epidemiology. Continued monitoring is needed in an era of emerging resistance.