6 – Langerhans Cell Histiocytosis
This multisystem disease can present as a severe diaper rash that is unresponsive to multiple topical therapies. Like the diaper rash of AE, Langerhans cell histiocytosis (LCH) has been described as a more malignant version of seborrheic dermatitis. Clinically, LCH appears as crusted papules with surrounding petechiae or pinpoint hemorrhage (Figure F). Lymphadenopathy may or may not be present, and if systemic progression has begun, the infant may be irritable or appear jaundiced. It is not advisable to wait for these symptoms to develop before proceeding with the systemic workup. When treating a patient with a particularly recalcitrant diaper dermatitis, it is appropriate to consider immediate referral to a pediatric dermatologist for punch biopsy to rule out cutaneous LCH. If the biopsy confirms the presence of Langerhans cells, then a full systemic workup and possible treatment with systemic therapy should be implemented by a pediatric oncologist, since diabetes insipidus, skeletal involvement, pulmonary disease, hepatic disease, or bone marrow involvement may develop in affected children.
Although each of the previous disease processes can present with the chief complaint of "diaper dermatitis," the astute clinician can distinguish among them on the basis of subtle differences and other clinical clues—and by careful follow-up to ensure that first-line treatment has led to the expected clinical improvement. When an infant fails to improve as expected, it is always helpful to question the original diagnosis and consider the more uncommon causes of diaper dermatitis.