disease as well as case reports often mirror those published in past decades in the developed world. the other 10% of cases are primarily caused by primary hyperplasia, or an increase of the number of cells. parathyroid carcinoma accounts for less than 1% of all cases, occurring most frequently in individuals around 50 years of age (in stark contrast to ofc as a result of primary hyperparathyroidism) and showing no gender preference. approximately 95% of hyperparathyroidism caused by genetic factors is attributed to men type 1. this mutation also tends to affect younger individuals. history friedrich daniel von recklinghausen, who is credited, along with gerhard engel, in naming ofc the condition was first described by gerhard engel in 1864 and friedrich daniel von recklinghausen in 1890, though william hunter, who died in 1783, is credited with finding the first example of the disease. "von recklinghausen's disease" (without the qualification "of bone") is a completely unrelated disorder, nowadays termed neurofibromatosis. in 1884, davies colley delivered a presentation to the pathological society of london that detailed the manifestation of hyperparathyroidism into a brown tumor of the mandible, as well as the histological makeup of the tumor. the discovery and subsequent description of the parathyroid glands is credited to ivar sandstrom, though his publication, on a new gland in man and several mammals-glandulae parathyroideae, received little attention. gustaf retzius and eugene gley compounded his research, the latter credited with the discovery of the function of the parathyroid glands. this research cumulated in the first surgical removal of a parathyroid tumor by felix mandel in 1925. a 2.5 × 1.5-inch (64 × 38 mm) tumor was removed from the thyroid artery of a man with advanced ofc. the patient's symptoms disappeared, only to return in approximately six years as a result of renal stones that were diagnosed only after the patient had died. in 1932, blood tests on a female patient with renal stone-based ofc revealed extremely high blood calcium levels. fuller albright diagnosed and treated the woman, who had a large tumor of the neck as well as renal stones. the first published literature to describe a brown tumor (which was linked to ofc) was published in 1953, though clinical reports from before 1953 do draw a correlation between the disease and tumors previous to the publication. the advent of the multichannel autoanalyzer in the 1960s and 70s led to an increase in early diagnosis of primary hyperparathyroidism. this increase led to a sharp decline in the prolonged manifestation of the disease, leading to a drop in the number of cases of ofc due to the early detection of hyperparathyroidism. before this invention, the diagnosis of primary hyperparathyroidism was generally prolonged until the emergence of severe manifestations, such as ofc.