<unk>  is very rare; there are fewer than 300 reported cases in medical literature. Although<unk>  can be found worldwide, almost a quarter of reported diagnoses are in South Africa. Many of these are in patients of Dutch, German, and Khoisan ancestry. This high frequency is thought to be due to the founder effect. Due to its recessive genetic cause and the ability to be a carrier of the disease without symptoms,<unk>  often runs in families. In some regions of South Africa, up to one in 12 individuals may be carriers of the disease. Most of the case studies involving<unk>  patients involve only one to three cases and these cases are often in the same family. Due to its low incidence, it is difficult to find a large enough number of cases to adequately study the disease.
Urbach–Wiethe disease
Brill–Zinsser disease
Koolen–De Vries syndrome
Camurati–Engelmann disease
DeSanto-Shinawi syndrome
Fox–Fordyce disease
Barakat-Perenthaler syndrome
Pelger–Huët anomaly