Annular rash in an elderly lady

WY Lai黎永耀, WYM Tang鄧旭明

HK Pract 2009;31:81-83

Summary

Superficial fungal infection is one of the most commonly encountered skin problems in family practice. A 62-year-old lady presented with persistent asymptomatic annular rash on her trunk and limbs for more than one year. She was found to have suspected Cushing syndrome which could possibly account for the atypical presentation. Systemic terbinafine with adjunctive topical treatment were given with excellent response.

摘要

淺部真菌感染是家庭醫生最常見的皮膚問題之一。一位62歲的長者身體及四肢出現無症狀的環型皮疹超過一年，可能是她患有皮質醇增多症（Cushing's syndrome）而產生的非典型病徵。使用系統性的抗真菌藥物特必奈芬輔以局部治療得到了很好的效果。

Introduction

Fungal infections of the skin and nails are a common global problem. About 20-25% of the world's population suffers from superficial fungal infection, involving skin, hair and nail. Pathogens responsible for skin mycoses are primarily anthropophilic and zoophilic dermatophytes from the genera Trichophyton (T.), Microsporum (M.) and Epidermophyton (E.).¹ According to a study at the National Skin Centre of Singapore, Trichophyton rubrum (T. rubrum) is the most frequent causative fungal pathogen² and often responsible for chronic dermatophytosis. There is some evidence that mannan produced by this fungus suppresses or diminishes the inflammatory response and the lack of or a defective cell-mediated immunity predisposes the host to chronic or recurrent dermatophyte infection.³ We herein report a case of chronic dermatophytosis with an unusual clinical presentation.

Clinical information

A 62-year-old lady presented with more than one year's history of persistent skin rash affecting her trunk and limbs. The rash increased in extent and became more obvious upon sun exposure but she remained asymptomatic. There was no fever, myalgia or joint pain. Her appetite and weight had remained stable. She reported no recent history of medication intake, including traditional Chinese medicine. She did not keep any pets at home and her family history was insignificant for skin disease.

Physical examination showed Cushingoid features with moon face, buffalo hump and central obesity (Figure 1). Pin-prick sensation was normal. There was no palpable lymphadenopathy and organomegaly. Detailed examination revealed widespread erythematous patches of varying sizes affecting the neck, limbs and trunk (Figures 2, 3, and 4). Some patches exhibited a well defined border with collarette of fine scales and central clearing with atrophic surface (Figure 4). Fingernails and toenails were normal.

The differential diagnoses included tinea corporis/incognito, mycosis fungoides, erythema annulare centrifugum, subacute lupus erythematosus and leprosy. Blood tests including complete blood picture, liver and renal function test, thyroid function, fasting glucose and lipid profile were normal. Morning cortisol was depressed. The erythrocyte sedimentation rate was 16. Auto-immune markers including anti-nuclear antibody (ANA), anti-extractable nuclear antibodies (anti-ENA), complements C3/C4 and immunoglobulin pattern were normal or negative.

Skin scrapings did not reveal any fungal elements by microscopic examination using potassium hydroxide (KOH); however, fungal culture revealed Trichophyton rubrum. A skin biopsy was performed before the culture result was available in order to exclude other possible serious causes such as mycosis fungoides or subacute lupus erythematosus. It showed fungal hyphae in the stratum corneum. Pustular collections were seen in the epidermis, while superficial perivascular infiltrate of lymphocytes and neutrophils were present in the dermis. Based on the above information, persistent and extensive dermatophytosis with tinea corporis due to possible Cushing Syndrome was diagnosed.

Progress

Terbinafine was given for 4 weeks consecutively with isoconazole as an adjunctive topical therapy. Complete resolution followed. Further workup for her Cushing syndrome was undertaken by the endocrinologist.

Discussion

Dermatophyte infections are capable of, and notorious for, demonstrating atypical patterns that can mimic other cutaneous diseases. Clinicians should be vigilant on cases where clinical presentation is unusual. Careful history taking and physical examination supported by relevant investigations are needed for making an accurate diagnosis which gives guide to the most appropriate treatment.

The differential diagnosis of tinea corporis includes a wide range of skin diseases such as lupus erythematosus, psoriasis, erythema annulare centrifugum, pityriasis rosea, nummular eczema, drug eruption, mycosis fungoides, erythema gyratum repens, sarcoidosis, leprosy, and secondary syphilis.^4,5 Because of the shared characteristic features in these diseases, it is important to consider all possibilities if the KOH examination is normal or if a patient fails to respond to appropriate treatment.⁶

In general, some factors may be particularly important to consider in order to explain the development of persistent or extensive fungal infections.⁷

1. Dry, intact epidermis Moist areas between toes in shoe-wearing populations and in the groin in males are particularly susceptible to fungal infections.
2. Epidermal turnover Persistent fungal infection sometimes occurs in patients with ichthyosis vulgaris and sex-linked ichthyosis, which probably results from reduced shedding of keratin rather than its slow turnover.
3. Sebum Unsaturated fatty acids of C9-C13 length is found in sebum. Resistance of the adult scalp to tinea capitis has been attributed to the presence of these fatty acids. Absence of sebum in certain areas such as toe clefts may be important, explaining in part their particular susceptibility to tinea.
4. Malnutrition Fungal infections have been shown to be more common in the malnourished and this may be attributable to depressed immunity and perhaps diminished cell turnover in the epidermis. Moreover, there may also be a diminution in the sebum level.
5. Metabolic and endocrine factor There is an increased susceptibility to fungal infections in patients with Cushing syndrome due to the diminished immune function.
6. Temperature With the notable exception of T.verrucosum, dermatophytes grow poorly at 37ﾟC. This may partly explain the fact that deep infections with dermatophytes are almost unknown. However, persistence of T. rubrum infections in the toenails among those with poor peripheral circulation is probably related to poor nail growth rather than low skin temperature per se.

Conclusion

Depending on various factors including host immune response, superficial fungal infections may have unusual presentations. In our case, the possibility of Cushing syndrome may explain the persistence and extensiveness of the skin lesion.

Key messages

1. Fungal infection of the skin and nails are a common global problem.
2. Trichophyton rubrum is the most prevalent fungal pathogen.
3. It is important to consider other differential diagnoses when encountering persistent and extensive annular rash especially if KOH examination is normal or if a patient fails to respond to appropriate treatment.