Erlenmeyer Flask Deformity

The Erlenmeyer flask deformity refers to the flaring of metaphyses of tubular bones and can be seen with:

• Chronic anemia: Hemoglobinopathies such as thalassemia and sickle cell disease.
• Hereditary multiple exostoses (shown above): Due to sessile lesions.
• Osteopetrosis:
• Niemann-Pick disease:
• Gaucher disease: Flask deformity due to impaired remodeling of the metaphyses of tubular bones.
• Metaphyseal dysplasias: Craniometaphyseal dysplasia, Pyle disease (familial metaphyseal dysplasia), etc.
• Metal poisoning: A late change in lead poisoning; fetal Magnesium toxicity.

Stupid mnemonic: Think of a bong made from an Erlenmeyer flask and used by Cheech and CHONG (Chronic anemia, Hereditary multiple exostoses, Osteopetrosis, Niemann-Pick, Gaucher disease). Add a couple of Ms for the munchies (Metaphyseal dysplasias and Metal poisoning), and you have the main causes.

References

• Faden MA, Krakow D, Ezgu F, Rimoin DL, Lachman RS. The Erlenmeyer flask bone deformity in the skeletal dysplasias. Am J Med Genet A. 2009 Jun;149A(6):1334-45.
• Heselson NG, Raad MS, Hamersma H, Cremin BJ, Beighton P. The radiological manifestations of metaphyseal dysplasia (Pyle disease). Br J Radiol. 1979 Jun;52(618):431-40.
• Wenstrup RJ, Roca-Espiau M, Weinreb NJ, Bembi B. Skeletal aspects of Gaucher disease: a review. Br J Radiol. 2002;75 Suppl 1:A2-12.