BSL is more prevalent in males (male to female ratio as high as 15:1) from Mediterranean or eastern European countries (Italy, Spain, France). Patients typically present between age 20 and 40.
It is thought that BSL may result from functionally defective brown adipose tissue. While chronic alcohol ingestion is the most commonly encountered association, there are reports in families with an autosomal dominant pattern and pediatric cases have been reported. BSL has also been associated with metabolic disease (impaired fasting glucose, diabetes, and hyperlipidemia) in obese patients.
Three types of lipoma distribution may occur.
Type 1: "Madelung collar" or "horse collar"
- More common in men
- Fat accumulation on neck, submental region, upper back
- Difficulty turning head
- Deep infiltration of mediastinal and pharyngeal structures leading to dyspnea, obstructive sleep apnea, dysphagia, dysphonia, superior vena cava compression.
- More common in women
- Diffuse fat accumulation on trunk and proximal extremities
- Large bilateral breast masses
- Lipomatous deposits have also been reported in the tongue (macroglossia), scrotum, and retro-orbital space.