MedGen

Pachyonychia congenita (PC) is characterized by hypertrophic nail dystrophy, painful palmoplantar keratoderma and blistering, oral leukokeratosis, pilosebaceous cysts (including steatocystoma and vellus hair cysts), palmoplantar hyperhydrosis, and follicular keratoses on the trunk and extremities. [from GeneReviews]

Steatocystoma multiplex is a skin disorder characterized by the development of multiple noncancerous (benign) cysts known as steatocystomas. These growths begin in the skin's sebaceous glands, which normally produce an oily substance called sebum that lubricates the skin and hair. Steatocystomas are filled with sebum.

In affected individuals, steatocystomas typically first appear during adolescence and are found most often on the torso, neck, upper arms, and upper legs. These cysts are usually the only sign of the condition. However, some affected individuals also have mild abnormalities involving the teeth or the fingernails and toenails. [from MedlinePlus Genetics]