Phalangeal microgeodic syndrome and pine processionary caterpillar

Area of Science:

• Pediatric Rheumatology
• Dermatology
• Pathology

Background:

• Phalangeal Microgeodic Syndrome (PMS) is a rare condition characterized by osteolytic lesions in the phalanges.
• The etiology of PMS remains largely unknown, with previous hypotheses suggesting circulatory disturbances.
• Differential diagnoses include sickle cell anemia, syphilis, osteomyelitis, tuberculosis, and sarcoidosis.

Observation:

• An 11-month-old girl presented with a one-month history of edematous fingers.
• She had a prior history of mucocutaneous reaction to a processionary caterpillar.
• Radiographs revealed small, round lytic lesions in the phalanges.

Findings:

• A bone biopsy confirmed fibrosis and foreign bodies resembling caterpillar hairs within an epithelioid granuloma in an osteolytic lesion.
• This led to a diagnosis of Phalangeal Microgeodic Syndrome (PMS).
• The findings suggest a potential link between environmental exposures, specifically caterpillar hairs, and the development of PMS.

Implications:

• This case presents the first documented instance of PMS in a child with a direct history of caterpillar exposure.
• It highlights the importance of considering environmental factors and specific exposures in the differential diagnosis of pediatric bone lesions.
• Further research is warranted to elucidate the role of environmental triggers in the pathogenesis of Phalangeal Microgeodic Syndrome.