The breed has been made popular by a number of royal owners since the 18th century. Queen Victoria owned a particularly small Pomeranian and consequently, the smaller variety became universally popular. During Queen Victoria's lifetime alone, the size of the breed decreased by half. Overall, the Pomeranian is a sturdy, healthy dog. The most common health issues are luxating patella and tracheal collapse. More rarely, the breed can have Alopecia X, a skin condition colloquially known as 'black skin disease'. This is a genetic disease which causes the dog's skin to turn black and lose all or most of its hair. As of 2013, in terms of registration figures, since at least 1998, the breed has ranked among the top fifty most popular breeds in the US, and the current fashion for small dogs has increased their popularity worldwide.