**Introduction**
Langerhans cell histiocytosis (LCH) is a rare condition that arises from Langerhans cells, a type of dendritic cell that helps the body fight infection. Mutations can develop in genes that control dendritic cell function, resulting in proliferation and buildup of Langerhans cells in different parts of the body, causing tissue damage or lesion formation. LCH commonly presents as rash and/or bony lesions.
**Case Description**
A 2-year-old with a history of frequent ear infections and pathologic fractures initially presented to clinic for evaluation of right wrist injury, nasal drainage, and flaky, scaly scalp. Previous medical history also included skin issues since birth, including acne and seborrheic capitis. X-ray of the wrist showed nondisplaced fracture of the distal right radius. Selenium shampoo for seborrheic dermatitis was prescribed. At a clinic visit 2 weeks later a pruritic rash beginning in the groin and spreading to the abdomen, along with worsening seborrheic dermatitis, impetigo of the face, and scabies were noted. Ketoconazole shampoo, cefdinir, and permethrin cream were prescribed, and referrals to Dermatology and Allergy/Immunology were placed due to concerns for an underlying condition causing extensive skin sensitivity and recurrent illnesses. A referral to Hematology/Oncology was also made due to concerns for LCH. Further labs were significant for elevated INR, uric acid, AST/ALT, and low Mg. A skin biopsy showed an increase in Langerhans cells within the hair follicle structure itself, most consistent with the follicular eczema of atopic dermatitis. The family reported an overall improvement in symptoms with prescribed therapies. Further testing with Allergy/Immunology came back negative for immunodeficiency. Elevated IgE was noted at that time, which Allergy/Immunology concluded was the most likely cause of severe atopy and recurrent ear infections.
**Discussion/Conclusion**
This case illustrates that atopic dermatitis can mimic LCH. LCH was suspected initially due to the patient's multiple skin issues and pathologic fractures. A skin biopsy led to the distinction between the two conditions. Follicular eczema is a form of atopic dermatitis that presents as individual papules including a central hair follicle. Pathologic features include perifollicular and perivascular lymphocytic inflammation of the follicular epithelium. Studies have shown the presence of IgE bearing Langerhans cells in atopic dermatitis, and this is associated with high serum IgE levels, as seen in this patient. Clinicians should be aware of these distinctions when presented with a patient with similar symptoms.
