Hematogenously disseminated skin disease caused by Mucor velutinosus in a patient with acute myeloid leukemia

Abstract

We report here a case of disseminated skin infection caused by Mucor velutinosus, a recently described new species. We believe this to be the first published report of a clinical case of mucormycosis due to M. velutinosus, as well as a rare case of dissemination from a deep site to skin.

Fig. 1.

A skin lesion produced by M. velutinosus and the histological sections of the biopsy specimen. (A) A circular lesion produced on the patient's forehead. (B to E) Histological sections of the skin biopsy specimen stained with H&E. Note that the early stages of chlamydospore formation in chains resemble septated hyphae (B, blue arrow) and the later stage shows a chain of chlamydospores (C, blue arrow). Hyphal elements typical of mucormycosis are indicated by red arrows in panels B and C. (D) Extensive growth of fungal hyphae around the blood vessel, and angioinvasion of hyphae (yellow arrows). Green arrows point to blood vessel walls. A higher magnification of the inset is seen in panel E; black arrows point to hyphae. Magnification of panels B and C is the same as in panel E.

Fig. 2.

Morphological characteristics of NIH1002 strain grown either on malt extract agar (A to F) or yeast nitrogen broth (G) at 30°C for 24 h. (A) Sympodially branched sporangiophores. (B and C) Subglobose (B) to conical (C) columellae. (D) Globose sporangiospores with thick verrucose walls. (E) Elongated to barrel-shaped chlamydospores produced in chains. (F) Rudimentary rhizoid formed from hyphae. (G) Yeast cells with multiple buds.

Fig. 3.

Molecular and phenotypic characterization of M. velutinosus. (A) Neighbor-joining tree based on the ITS1-5.8S rRNA-ITS2 sequence. The numbers at the nodes represent bootstrap values. The GenBank accession number of each sequence is indicated in parentheses. The bar indicates genetic distance. (B) Comparison of colony morphology and growth rate between the ex-type strain of M. velutinosus (UTHSC 02-1981) and NIH1002 on malt extract agar (MEA) and potato dextrose agar (PDA) media at 23, 30, and 37°C.