Atypical disseminated cutaneous histoplasmosis in an immunocompetent child, caused by an "aberrant" variant of histoplasma capsulatum var. capsulatum

Disseminated cutaneous-only histoplasmosis in a patient with AIDS

Histoplasmosis is an opportunistic fungal infection that occurs predominantly in immunocompromised patients. Cutaneous lesions in histoplasmosis are rare and typically occur in the absence of extra-cutaneous manifestations. We present a rare case of disseminated cutaneous-only histoplasmosis in a patient with recently diagnosed AIDS.

[Rapid identification of Histoplasma capsulatum in culture lysates]

BACKGROUND

Histoplasma capsulatum is the agent of histoplasmosis, a deep mycosis mainly afflicting immunocompromised patients. Rapid identification of the fungus isolated from clinical specimens allows timely administration of specific treatment.

AIM

To assess the ability of a dual PCR system targeting specific H. capsulatum DNA sites to identify fungal species in simple aqueous lysates from cultured fungi.

METHODS

We analysed the performance of two independent PCR reactions designed to amplify fragments of 111 and 279 bp included in H. capsulatum-specific gene AgM. We used 248 H. capsulatum strains and 68 isolates of other fungal species. Reaction templates consisted of aqueous lysates of cultured fungi (either in mycelial or yeast phase) obtained after three cycles of boiling and immediate cooling at 0°C. Selected strains were submitted to conventional DNA extraction and/or sequencing.

RESULTS

Both PCR systems performed identically. Amplification from aqueous lysates was achieved from 239 H. capsulatum strains; the remaining 9 strains only showed specific bands when purified DNA was used as template. Of all other fungal species tested, only 2 Emmonsia crescens strains amplified H. capsulatum-specific bands and sequences of their amplified PCR products matched > 97% with H. capsulatum sequences. Total test time did not exceed 7h with 96% sensitivity, 97% specificity and 99% positive predictive value.

CONCLUSIONS

The assay is fast, accurate and economical, and can be an alternative method for presumptive identification of H. capsulatum in simple culture lysates.

Typing of Histoplasma capsulatum strains by fatty acid profile analysis

The performance of fatty acid profiling for strain differentiation of Histoplasma capsulatum was assessed. Total fatty acids were isolated from the yeast-phase cells of seven stock and two previously unreported clinical strains of H. capsulatum var. capsulatum, as well as from one unreported clinical strain and one stock strain of H. capsulatum var. duboisii, and one strain of each of three other dimorphic zoopathogenic fungal species, Blastomyces dermatitidis, Paracoccidioides brasiliensis and Sporothrix schenckii. Different colony morphology and pigmentation types of the H. capsulatum strains were also included. The most frequently occurring fatty acids were oleic, palmitic, stearic and linoleic acids. There were variations in the relative percentage fatty acid contents of H. capsulatum strains that could be used for strain identification and discrimination. Differentiation between H. capsulatum strains was achieved by the comparison of detected fatty acids accompanied by principal component analysis using calculated Varimax-rotated principal component loadings. Statistical analysis yielded three major principal components that explained over 94 % of total variance in the data. All the strains of H. capsulatum var. capsulatum RFLP classes II and III were grouped into two distinct clusters: the heterogenic RFLP class I formed a large, but also well-defined group, whereas the outgroup strains of H. capsulatum var. duboisii, B. dermatitidis, P. brasiliensis and S. schenckii were shifted away. These data suggest that fatty acid profiling can be used in H. capsulatum strain classification and epidemiological studies that require strain differentiation at the intraspecies level.

Phylogeography of the fungal pathogen Histoplasma capsulatum

Until recently, Histoplasma capsulatum was believed to harbour three varieties, var. capsulatum (chiefly a New World human pathogen), var. duboisii (an African human pathogen) and var. farciminosum (an Old World horse pathogen), which varied in clinical manifestations and geographical distribution. We analysed the phylogenetic relationships of 137 individuals representing the three varieties from six continents using DNA sequence variation in four independent protein-coding genes. At least eight clades were idengified: (i) North American class 1 clade; (ii) North American class 2 clade; (iii) Latin American group A clade; (iv) Latin American group B clade; (v) Australian clade; (vi) Netherlands (Indonesian?) clade; (vii) Eurasian clade and (viii) African clade. Seven of eight clades represented genetically isolated groups that may be recognized as phylogenetic species. The sole exception was the Eurasian clade which originated from within the Latin American group A clade. The phylogenetic relationships among the clades made a star phylogeny. Histoplasma capsulatum var. capsulatum individuals were found in all eight clades. The African clade included all of the H. capsulatum var. duboisii individuals as well as individuals of the other two varieties. The 13 individuals of var. farciminosum were distributed among three phylogenetic species. These findings suggest that the three varieties of Histoplasma are phylogenetically meaningless. Instead we have to recognize the existence of genetically distinct geographical populations or phylogenetic species. Combining DNA substitution rates of protein-coding genes with the phylogeny suggests that the radiation of Histoplasma started between 3 and 13 million years ago in Latin America.

Oral histoplasmosis in Brazil

OBJECTIVE

We report 10 cases of histoplasmosis with oral manifestations seen in a teaching hospital in Brazil.

STUDY DESIGN

This is a retrospective study of the sociodemographic, clinicopathologic, and treatment data of these cases.

RESULTS

Overall, 8 of 10 cases were seropositive for human immunodeficiency virus (HIV), whereas 2 were negative. The predominant oral manifestations found in HIV-seropositive patients were ulcers, oral pain, and odynophagia; both of the HIV-seronegative patients were symptom-free. HIV infection was suspected in 7 cases because of the presence of oral lesions of histoplasmosis. Asthenia, fever, weight loss, lymphadenopathy, and hepatosplenomegaly were found only in HIV-seropositive patients. Radiographs in 3 out of 10 patients suggested pulmonary involvement. Amphotericin B was the antifungal therapy chosen, and clinical remission of oral lesions occurred in an average of 30 days (accumulated doses: 500-1500 mg). Itraconazole was very effective as a follow-up treatment in terms of prevention of recurrence.

CONCLUSION

Histoplasmosis only rarely affects HIV-seronegative patients; however, the possibility of hidden immunodepression should be considered when oral manifestations of histoplasmosis are present.