Familial hypocalciuric hypercalcemia (FHH) is an inherited condition that can cause hypercalcemia, a serum calcium level typically above 10.2 mg/dL; although uncommon. It is also known as familial benign hypocalciuric hypercalcemia (FBHH) where there is usually a family history of hypercalcemia which is mild, a urine calcium to creatinine ratio <0.01, and urine calcium <200 mg/day. Signs and symptoms
Most cases of familial hypocalciuric hypercalcemia are asymptomatic. Laboratory signs of FHH include:
High blood levels of calcium (hypercalcemia)
A low amount of calcium excreted in the urine (Ca excretion rate < 0.02 mmol/L)
High blood levels of magnesium (hypermagnesemia)
High normal to mildly elevated parathyroid hormone

Causes
Types include:

Pathogenesis
Most cases of FHH are associated with loss of function mutations in the calcium-sensing receptor (CaSR) gene, expressed in parathyroid and kidney tissue. These mutations decrease the receptors sensitivity to calcium, resulting in reduced receptor stimulation at normal serum calcium levels. As a result, inhibition of parathyroid hormone release does not occur until higher serum calcium levels are attained, creating a new equilibrium. This is the opposite of what happens with the CaSR sensitizer, cinacalcet. Functionally, parathyroid hormone (PTH) increases calcium resorption from the bone and increases phosphate excretion from the kidney which increases serum calcium and decreases serum phosphate. Individuals with FHH, however, typically have normal PTH levels, as normal calcium homeostasis is maintained, albeit at a higher equilibrium set point. As a consequence, these individuals are not at increased risk of the complications of hyperparathyroidism.Another form has been associated with chromosome 3q.
Additional treatment may include sodium bicarbonate for metabolic acidosis, and hemodialysis or hemodiafiltration to remove methanol and formate from the blood. Folinic acid or folic acid is also administered to enhance the metabolism of formate. History
There are cases of methanol resistance, such as that of Mike Malloy, whom someone tried and failed to poison by methanol in the early 1930s.In December 2016, 78 people died in Irkutsk, Russia from methanol poisoning after ingesting a counterfeit body lotion that was primarily methanol rather than ethanol as labeled. The body lotion, prior to the event, had been used as a cheap substitute for vodka by the impoverished people in the region despite warnings on the lotions bottles that it was not safe for drinking and long-standing problems with alcohol poisoning across the country.During the COVID-19 pandemic, Iranian media reported that nearly 300 people had died and over a thousand became ill due to methanol poisoning in the belief that drinking the alcohol could help with the disease. In the United States, the Food and Drug Administration discovered that a number of brands of hand sanitizer manufactured in Mexico during the pandemic contained methanol, and urged the public to avoid using the affected products. See also
Ethylene glycol poisoning

References


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