This disorder is a variant of the condition known as hypoparathyroidism. The latter was first described in the middle of the 20th century by Fuller Albright, an American endocrinologist. Hypoparathyroidism is a disease resulting from lack of the parathyroid hormone or PTH. Pseudohypoparathyroidism has many of the same signs and symptoms but arises because the target organs are not responsive to PTH. To complicate the clinical picture, certain other organs such as the thyroid and gonads may also fail to respond to the hormones that normally stimulate them.
The full clinical picture is sometimes called Albright hereditary osteodystrophy. Patients are short in stature with a short neck, chubby cheeks, round face, and a flattened nasal bridge. The fourth and fifth fingers and toes are often abnormally short. The teeth are late to erupt and have a defective coat of enamel. It is not unusual that patients have cognitive deficits and some have been described as mentally retarded. Tetany spasms and seizures are experienced by some individuals. Blood levels of calcium are low while those of phosphate are high.
Left untreated, cataracts can develop in children late in the first decade of life. Other children have poor vision secondary to swelling of the optic nerves that carry visual impulses to the brain. This can result in poor vision and nystagmus (searching movements of the yes).
This condition, of which there are a number of variants, is often the result of mutations in a gene. Only one of a pair needs to be changed to cause it and therefore it can be transmitted directly from generation to generation in what is called an autosomal dominant pattern. However, the clinical features vary somewhat depending upon whether the disease is inherited from the mother or father. Those who inherit the disease from the mother tend to have more severe features whereas those who receive the mutation from the father are mildly affected. The mechanism for this is called imprinting and is as yet poorly understood. More females than males have this condition.
Parents with pseudohypoparathyroidism can expect that half of their offspring will inherit this condition.
The physical appearance may arouse suspicion at birth but many infants and children are not diagnosed until later when their psychomotor development falls behind. A few are correctly identified when nystagmus and poor vision become evident. Complete physical and ocular examinations are required but the low serum levels of calcium and elevated levels of phosphate should suggest the diagnosis.
Early correction of the calcium and phosphate levels should prevent some of the more serious consequences of this syndrome.