Rapidly enlarging scalp nodules in a 20-month-old child

The differential diagnosis of subcutaneous scalp nodules in babies and toddlers is broad and includes benign, infectious and malignant entities. Multiple rapidly growing nodules may be alarming, but benign causes include subcutaneous granuloma annulare, deep infantile hemangioma and juvenile xanthogranuloma (deep subtype). Less commonly, infections such as deep fungal and nontuberculous mycobacterial infections may present as multiple nodules but are often associated with fever, secondary skin findings and satellite lesions. Finally, it is important to rule out diagnoses that carry high morbidity or mortality. Several malignancies may present this way, such as Langerhans cell histiocytosis, rhabdomyosarcoma, lymphoma, leukemia and metastatic neuroblastoma. Here, Ghazawi et al examine the case of a 20-month-old girl with multiple rapidly growing, painless, subcutaneous scalp nodules.