Tall stature in children: differential diagnosis and management

Tall stature is defined as height above 97th percentile for age and sex or more than 2SD above the mean for a defined population. It means 3 out of every 100 children in a community are tall and should be evaluated. Familial tall stature also known as constitutional tall stature is the most common cause of tall stature. The height is consistently above 97th percentile percentile and mid paretal height too is above 90th or 97th percentile. Usually occurs in a female child and the mother often remembers her unusual tall stature during her childhood. The bone as is marginally to moderately advanced so that the final height prediction is not very heigh. Physical examination is normal and lab tests, if obtained, are negative. The second most common cause of tall stature is nutritional. The height as well as the weight are at higher percentile. Again the bone age is maginally to moderately advanced so that final predicted adult height is not too much. Hormonal causes of tall stature include hyperthyroidism, precocious puberty and growth hormone excess. Hyperthyroidism is more common in girls and is almost always caused by Grave’s disease.The bone age is moderately advanced so that the final adult height is usually compromised. In cases of precocious puberty, although due to anabolic effects of sex steroids, the child is tall at the onset, the ultimate adult height is compromised due to premature epiphyseal fusion caused by oestrogen. Again, although, delayed puberty may be associated with short stature in childhood, as with constitutional delay, failure to eventually enter puberty and complete sexual maturation may result in sustained growth in adult life, with ultimate tall stature [1]. GH hormone excess causes gigantism in childhhod and acromegaly in adults. Gigantism is characterized by tall stature, broad hands and feet, prognathism, broad root of nose, excessive sweating, hypertension and glucose intolerance. Almost each and every part of the body is affected and large for age. GH levels are consistently high and can exceed 100 ng/ml [2]. Serum IGF-1 and IGFBP-3 are raised and serve as a sensitive screening tool for GH excesses. But the gold standard for making the diagnosis of GH excess is the failure to suppress serum GH levels below 5 ng /dl after 1.75 gm/ kbw glucose challange. This test measures the ability of IGF-1 to suppress GH secretion, because the glucose load results in insulin secretion, leading to suppression of IGFBP-1 which results in an acute increase in serum free IGF-1 level. There are some important chromosomal and syndromic causes of tall stature in children. Klinefelter’s syndrom (XXY) is the commonest chromosomal disorder affecting males (in 500-1000 boys). It should be suspected in boys with delayed puberty with tall stature, small and firm testes, eunochoid body proportions (decreased U/L segment) and gynaecomastia. And if these features are accompanied by delayed bone age it is almost diagnostic of Klinefelter syndrom. Serum levels of LH and FSH are raised and serum testosterone is markedly diminished. Homocystinuria is an autosomal recessive inborn error of aminoacid metabolism due to deficiency of cystathionine synthase. The gene is located on chromosom 21. It is characterized by tall stature, arachnodactyly, mental retardation and various occular manifestations. There is characteristic inferior subluxation of lens. Lab investigation includes positive cyanide nitroprucide test in urine as well as presence of homocystein in the urine. This condition is to be differentiated from Marfan syndrom which is characterized by defective fibrillin gene on chromosom 15, resulting in abnormal synthesis of fibrillin, a glycoprotein that is the major constituent of microfibrills Department of pediatrics, Sri Krishna Medical College & Hospital, Muzaffarpur, Bihar, India Kumar International Journal of Pediatric Endocrinology 2013, 2013(Suppl 1):P53 http://www.ijpeonline.com/content/2013/S1/P53