Multiple Consecutive Episodes of Cutaneous Larva Migrans with Prolonged Incubation Periods in a One-year-old Returning Traveler in Germany

To the Editors: Cutaneous larva migrans (CLM) is a skin condition caused by the penetration and migration of larval nematodes, most commonly Ancylostoma species, which is typically acquired in tropical and subtropical regions through contact with contaminated soil or sand. A previously healthy 1-year-old child from Germany was diagnosed with CLM with multiple consecutive lesions and notably prolonged as well as varied incubation periods. The initial presentation occurred a few days after returning from a 2-week vacation in the Maldives and Sri Lanka with a skin lesion on the right pretibial area (Fig. 1A). The parents reported only 20 minutes of beach exposure in the Maldives, where the child sat in the sand wearing only a diaper. The pediatrician diagnosed the serpiginous erythematous track as CLM, and the lesion resolved within 6 weeks with a watch-and-wait approach.FIGURE 1.: Multiple consecutive manifestations of cutaneous larva migrans. A: Initial lesion on the right pretibial area around 2 wk after exposure. B: Second lesion 3.5 mo after exposure. C: Third lesion 4 mo after exposure. D–F: Development over the course of 3 d of a new lesion 5 mo after exposure (D: day 1, E: day 2, F: day 3).A second lesion appeared on the left buttock 3.5 months postexposure. Initially, it was treated with topical corticosteroids under the presumptive diagnosis of eczema, reducing the symptoms. Days later, a thread-like track toward the anus developed (Fig. 1B). At 4 months, a third serpiginous track appeared near the second, moving toward the scrotum (Fig. 1C). Both lesions resolved within weeks with only topical corticosteroid treatment. Five months post-exposure, a fourth lesion appeared as a red papule on the left buttock. Evaluation in our outpatient department for tropical medicine revealed mild eosinophilia (0.56 thousand/μL, Ref. 0.0–0.3 thousand/μL). Stool microscopy, stool cultures and serology for gnathostomiasis, Toxocara canis and Stongyloides ssp. were all negative. The lesion evolved into a serpiginous track within days (Fig. 1D–F). Off-label ivermectin treatment (3 mg) was planned but deferred due to a diarrheal episode. A fifth lesion appeared at 6 months post-exposure. Off-label treatment of the child weighing 10 kg with ivermectin 3 mg as a single dose was then administered and tolerated well, with no new lesions observed in the following 3 months. This case of 5 consecutive CLM lesions is unusual due to prolonged and varied incubation periods following a single exposure event. Typically, multiple lesions appear simultaneously after exposure.1,2 In other cases, varied incubation periods are explained by multiple exposures.1 However, host factors and infection with various Ancylostoma species have been hypothesized to influence incubation periods.1,3 Some authors suggest larvae may remain dormant for months after infection,4 and ivermectin treatment might induce a dormant larval stage.5 In our case, multiple exposures and drug effects can be excluded. While infection with various Ancylostoma species could potentially explain this presentation, the restricted exposure time and location make this unlikely. The proximity of lesions on the buttock might suggest a single larva with different activity stages, but the missing track between initial lesions reduces this likelihood. Infection with multiple larvae appears more probable. CLM is typically self-limiting but can cause significant discomfort, especially in young children. Initial misdiagnosis as eczema is common due to nonspecific early presentation. Corticosteroids may reduce symptoms without addressing the underlying parasitic infection. Ivermectin effectively treated this case, stopping new lesion formation after a single dose. However, treatment failure and relapse have been reported.5 Ivermectin’s safety and efficacy in children <15 kg have been documented for scabies treatment.6 Off-label ivermectin should be considered for patients <15 kg with multiple CLM episodes.