Primary cutaneous mucormycosis caused by Mucor irregularis in an immunocompetent patient

Abstract

Primary cutaneous mucormycosis caused by Mucor irregularis in an immunocompetent patientDear Editor, Mucormycosis, which mainly affects immunocompromised patients, is a rare, life-threatening infection caused by the order Mucorales. Among the six clinical types of mucormycosis, 1 cutaneous mucormycosis is the rarest and is further categorized into two types: (i) the gangrenous type, which only occurs in immunocompromised patients and progresses rapidly, and (ii) the superficial type, which develops in immunocompetent individuals, manifests as erythematous plaques, and progresses slowly. 2 We present a case of superficial cutaneous mucormycosis caused by Mucor irregularis (M. irregularis) involving an immunocompetent patient.A 16-year-oldJapanese boy who was otherwise healthy presented with a 1-year history of a gradually enlarging plaque on his leg. A physical examination demonstrated an erythematous plaque exhibiting slight desquamation on his lower right leg, which he had scraped in a bicycle accident 2 years before (Fig. 1a). A histopathological examination detected a suppurative granuloma containing neutrophils, lymphocytes, and multinucleated giant cells in the dermis (Fig. 1b). Broad, ribbon-like, hyaline, aseptate hyphae were also observed (Fig. 1c). However, fungal hyphae and microvascular thrombosis were not detected in his blood vessels. Skin tissue specimens and skin scales cultured on Sabouraud dextrose agar at 25°C yielded wool-like, light yellow colonies, but no colony growth occurred at 38°C (Fig. 1d). Microscopic examinations of slide cultures detected sporangiophores, which had formed a terminal, globose sporangium. No apophyses were observed (Fig. 1e). These findings were consistent with Mucor fungi, and the isolate was identified as Mucor irregularis based on sequencing of the D1/D2 domain of the large subunit rRNA gene (GenBank accession no. IFM 57177).Before obtaining a diagnosis, we tried itraconazole (100 mg/ day), fluconazole (200 mg/day), and voriconazole (300 mg/day), independently, as empirical therapies, but none of them was effective. However, when we administered high-dose itraconazole (400 mg/day), the patient's plaque gradually regressed. Itraconazole was administered for a total of 9 weeks (Fig. 1f). No recurrence has been observed for 5 years.M. irregularis was originally known as Rhizomucor variabilis, but it was renamed M. irregularis based on its DNA sequence. Cases of mucormycosis due to M. irregularis are rare, and only 14 cases have been reported in the English-language literature.3-5 However, it is worth noting that mucormycosis due to M. irregularis presents with unique clinical features. In contrast to classical mucormycosis, most M. irregularis infections affect immunocompetent patients and do not exhibit angioinvasion, especially in the early stages. Moreover, the majority of M. irregularis infections manifest as the superficial cutaneous type, progress chronically, and persist for several years on exposed sites. It is unknown why M. irregularis infections display the...

Cutaneous mucormycosis

“…27 These skin lesions were infiltrated plaques, ulcers and nodules, which usually remained localized and gradually expanded over months and years. 21-23 …”

Cutaneous Mucormycosis: Mycological, Clinical, and Therapeutic Aspects

“…Most lesions arise as erythematous plaques that progressively show central necrosis, peripheral erythema, and ulceration. If no treatment is administered, fungi can penetrate into fascia (developing necrotizing fasciitis or gangrene), muscle, tendons, and bone; the latter is characterized by fistulae formation due to osteolysis [10,11,14,25,28]. The skin lesions usually progress slowly; however, some cases may be aggressive, developing gangrene [8•, 10, 11, 50-52].…”

“…Rhizopus arrhizus (formerly Rhizopus oryzae) is the main etiological agent for mucormycosis, contributing with 47 to 85 %; however, CM cases are frequently due to: Apophysomyces elegans (complex) [12,13,16,17], Apophysomyces trapeziformis [16, 18, 19•], Lichtheimia corymbifera [14,16,20], Lichtheimia ramosa [16,21], Saksenaea vasiformis [12,13,16,17,22], Mucor irregularis (formerly Rhizomucor variablilis) [16,[23][24][25][26], Rhizopus arrhizus [3, 4, 9•, 12, 15, 16], and Mucor sp. [9•, 12, 15, 16].…”

“…A new species, Apophysomyces mexicanus [29•], has been recently reported from a warm-humid zone at Mexico, sharing climate characteristics with some areas from India. M. irregularis cases are commonly reported from Asian countries (China, India, and Japan) [16,[23][24][25][26].…”

Changing Epidemiology of Mucoralean Fungi: Chronic Cutaneous Infection Caused by Mucor irregularis

“…Since then, most of the cases of cutaneous mucormycosis by M. irregularis have been reported in Asia mainly from China with the exception of two cases from southern India. Outside Asia cases have been reported from Japan, Australia and USA [2][3][4][5][11][12][13][14][15]. This is the first time that a case of M. irregularis is being reported from northern India (Punjab), causing typical presentation of primary chronic cutaneous mucormycosis.…”