What is encephalitis and what best describes the most common cause of encephalitis?

A. Renal agenesis: failure of an organ (renal) to develop: Renal agenesis is the complete absence of one or both kidneys due to failure of development during fetal life. Bilateral agenesis is often fatal, while unilateral agenesis can be asymptomatic if the remaining kidney functions well.

B. Renal hypoplasia: failure of kidney to develop to normal size and contains fewer renal lobes: In renal hypoplasia, the kidney is structurally normal but smaller than average and contains fewer nephrons or lobes. This congenital condition may be unilateral and asymptomatic or bilateral and lead to renal insufficiency.

C. Renal dysgenesis: failure of an organ (kidney) to develop normally: Renal dysgenesis refers to abnormal development of the kidney structure, resulting in malformations that can impair function. It often involves malformed or nonfunctional renal tissue.

D. Renal dysgenesis: failure of an organ (kidney) to develop: This description better defines renal agenesis rather than dysgenesis, which implies abnormal rather than absent development.

A. May be idiopathic: In many cases, especially central precocious puberty, no identifiable underlying cause is found. This is referred to as idiopathic precocious puberty and is a common diagnosis, particularly in girls.

B. Peripheral precocious puberty is independent of gonadotropin release from the pituitary gland: Peripheral (or gonadotropin-independent) precocious puberty occurs due to hormone secretion from sources other than the pituitary, such as adrenal tumors or ovarian cysts.

C. Central precocious puberty is caused by premature activation of the hypothalamic-pituitary-gonadal (HPG) axis: This is the most common form and involves early activation of the normal puberty pathway via the HPG axis.

D. It is defined as the onset of secondary sexual characteristics before age 8 in girls and age 9 in boys: This is the widely accepted medical definition of precocious puberty based on chronological age for the appearance of secondary sexual characteristics.

E. Tall stature during childhood is a common feature, but final adult height may be shorter than expected without treatment: Early growth spurts can lead to early closure of growth plates, resulting in reduced adult height if untreated.