An Unexplained Lesion on the Leg of a 2-year-old Girl

An otherwise healthy 2-year-old girl is referred to our clinic for assessment of a lesion on the right lower leg. After a trip to Mexico 15 months prior, the parents first noticed what they describe as a “tan” on the posterior aspect of her right lower leg, followed by a scaly round plaque that would come and go. There has been no pain or pruritus. She was prescribed mometasone furoate ointment, which had some benefit. She later developed red-to-purple nodules in the same area. The patient was seen by multiple providers and was prescribed a combined fusidic acid (antibiotic) and hydrocortisone 1% ointment, a 1-week course of oral cephalexin, and betamethasone valerate 0.05% ointment; each without any improvement.The patient lives in a house in an urban area. She has not had contact with any animals. There are no noted exposures to insect bites or changes in clothing or detergents. The family history is noncontributory.On physical examination, the patient appears healthy. On the right leg, there are multiple violaceous coalescent plaques with overlying erythematous papules with scale (Fig 1) with no drainage or edema. The skin is otherwise smooth and clear. There are small, mobile lymph nodes palpable in the right inguinal canal. Findings on the rest of the physical examination are normal, including range of motion of the ankles, knees, and hips and a normal gait. There is no hepatosplenomegaly.Laboratory investigation completed prior to referral to our center revealed a white blood cell count of 12.2 × 109/L (normal 5.0–12.0 × 109/L) with 52% neutrophils, 43% lymphocytes, and 0.4% eosinophils. Alanine aminotransferase was elevated at 91 U/L (normal <44 U/L) with a normal aspartate aminotransferase of 48 U/L (normal <52 U/L).Two years after the eruption of the lesion, a punch biopsy is completed and the patient is started on ketoconazole 2% cream while awaiting results; histology reveals a neutrophilic dermatosis. A fungal scraping and culture are sent, and the patient is started on a tapering course of prednisolone with some mild improvement; however, both fungal scraping and culture are negative for fungal elements and bacteria. Pathology results from the biopsy reveal the diagnosis.A skin biopsy from the primary lesion reveals perifollicular inflammation with mixed infiltrate of lymphocytes, neutrophils, and eosinophils with acanthosis and spongiosis, consistent with the presumptive clinical diagnosis of Majocchi granuloma. It is sometimes not possible to see the organism on histopathology either due to significant inflammation or it may be missed in the plane of the section.Majocchi granuloma is a deep granulomatous folliculitis due to a fungal infection from a dermatophyte in the dermis. (1)(2) Dermatophytes enter the hair follicle and cause an inflammatory response in the dermis. (3) Majocchi granuloma typically appears as a well-circumscribed, annular and irregular scaly plaque with follicular papules, pustules, or nodules. (2)(4) Lesions most typically appear on the lower extremities but can develop anywhere on the body, and in children lesions develop more commonly on the head and neck. (3)(4) There are 2 distinct forms: a local dermal infection occurring in an immunocompetent host, and a deep subcutaneous nodular form in immunocompromised patients. (2)(5) Pain and pruritus are the most common associated symptoms, although many patients are asymptomatic. (3)Majocchi granuloma is most commonly caused by Trichophyton rubrum, Trichophyton mentagrophytes, or Microsporum canis, which is most the common in children. (3) In superficial dermatophyte infections, including tinea corporis and tinea pedis, fungal pathogens invade only the stratum corneum, the outermost layer of the epidermis. (6) In contrast, deep or invasive dermatophyte infections, including Majocchi granuloma, involve dermatophytes invading the dermis. Histopathology typically demonstrates a mixed infiltrate including neutrophils and eosinophils. (3)Risk factors for development of Majocchi granuloma include immunosuppression, topical steroid use, superficial fungal infections, animal exposure, and local trauma (such as shaving). (3)(5)The differential diagnosis for Majocchi granuloma includes superficial fungal infections, such as tinea corporis, allergic contact dermatitis, and bacterial folliculitis. Allergic contact dermatitis has pruritus as a primary symptom and should respond to topical steroids. Bacterial folliculitis should respond to standard treatment with cephalexin. Although these lesions can be difficult to differentiate, a clinician should consider Majocchi granuloma when standard treatments for more common diagnoses are unsuccessful.Patients are often prescribed topical corticosteroids and/or topical antifungals for treatment based on clinical appearance. Topical corticosteroids may disrupt the skin barrier, with local immunosuppression allowing for dermatophyte entry into hair follicles. (7) Topical antifungals are unable to adequately penetrate the follicle. Treatment of Majocchi granuloma requires systemic antifungal therapy. Commonly used systemic antifungals include terbinafine or griseofulvin for 1 to 6 months or until resolution of symptoms. Itraconazole could also be considered. Systemic ketoconazole is no longer recommended in children because of reports of serious hepatotoxicity and death. (8) Terbinafine is commonly used although it is off-label in young children. The following common dosing guidelines are used: less than 20 kg, 62.5 mg daily; 20 to 40 kg, 125 mg daily; greater than 40 kg, 250 mg daily. At our center, if a course of terbinafine is likely to be several months, liver enzymes and a complete blood cell count are checked prior to initiating treatment, mid-therapy, and at the end of a course of treatment; however, recent literature suggests that this practice appears to be unnecessary in otherwise healthy children. (9)The patient was treated with oral terbinafine 62.5 mg daily for 6 weeks, with substantial improvement. An abdominal ultrasound and hepatology referral did not identify a cause of the mild liver injury. The patient was transitioned to topical terbinafine and betamethasone valerate. Four months after discontinuing the systemic antifungal, the family noticed new scattered perifollicular papules; a second course of oral terbinafine was used for 6 weeks with improvement. Another relapse prompted a third course of oral terbinafine for 8 weeks. At follow-up 5 years after the initial lesion, the Majocchi granuloma had cleared and remained inactive (Fig 2).

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