Phalangeal microgeodic syndrome and pine processionary caterpillar.

We describe an 11-month-old-girl with a 1-month history of edematous fingers. She had been hospitalized 3 months before for a mucocutaneous reaction to a processionary caterpillar. Manifestations of arthritis or systemic illness were absent. Radiographs of fingers showed small round lytic lesions within the middle and distal phalanges. A diagnosis of 'Phalangeal Microgeodic Syndrome' (PMS) was established. Bone biopsy of an osteolytic lesion showed fibrosis and foreign bodies with hair aspect surrounded by an epithelioid granuloma. PMS signs include sub-acute swelling and redness of fingers associated with microgeodic osteolytic lesions of phalanges. Sickle-cell anemia, syphilis, osteomyelitis, tuberculosis and sarcoidosis are the main differential diagnoses to exclude. The etiology is still unknown. Circulatory disturbances in the phalanges exposed to low temperatures have been mentioned by several authors. We describe the first case of PMS in a child with a clear history of play with a caterpillar and the presence of a caterpillar hair with epithelioid granuloma in an osteolytic lesion.