Introduction to Hypervitaminosis A

Chronic hypervitaminosis A results from excessive ingestion of vitamin A for several weeks or months.

Toxicity can be induced in adults and children with chronic daily intakes of 15,000 g and 6,000 g, respectively. Symptoms subside rapidly on withdrawal of the vitamin.

Signs of subacute or chronic toxicity may include headache; vomiting; anorexia; dry, itchy desquamating skin; seborrheic cutaneous lesions; fissuring at the corners of the mouth; alopecia and/or coarsening of the hair; bone abnormalities; swelling of the bones; enlargement of the liver and spleen; diplopia; increased intracranial pressure; irritability; stupor; limited motion; and dryness of the mucous membranes. In addition, desquamation of the palms and the soles of the feet is common.

Radiographs show hyperostosis affecting several long bones, especially in the middle of the shafts . Serum levels of vitamin A are elevated. Hypercalcemia and/or liver cirrhosis may be present. Hypervitaminosis A is distinct from cortical hyperostosis.
In young children, toxicity is associated with vomiting and bulging fontanelles. An affected child has anorexia, pruritus, and a lack of weight gain. Acute hypervitaminosis A toxicity has occurred in infants in developing countries after ingestion of very high amounts of vitamin A during vaccine administration. Symptoms include nausea, vomiting, and drowsiness; less common symptoms include diplopia, papilledema, cranial nerve palsies, and other symptoms suggestive ofpseudotumor cerebri. Severe congenital malformations occur in infants of mothers who consumed therapeutic doses (0.5–1.5 mg/kg) of oral 13-cis-retinoic acid during the 1st trimester of pregnancy for treatment of acne or cancer. This results in a high incidence (>20%) of spontaneous abortions and birth defects.

Introduction to Impetigo

A contagious, superficial skin infection, impetigo (also known as impetigo contagiosa) occurs in nonbullous and bullous forms. This vesiculopustular eruptive disorder spreads most easily among infants, young children, and the elderly.

Predisposing factors—such as poor hygiene, anemia, malnutrition, and a warm climate—favor outbreaks of this infection, most of which occur during the late summer and early fall. Impetigo can complicate chickenpox, eczema, and other skin conditions marked by open lesions.

Causes
Coagulase-positive Staphylococcus aureus and group A beta-hemolytic streptococci (or a combination of both) produce epidermal infections.

Signs and symptoms
Common nonbullous impetigo typically begins with a small red macule that turns into a vesicle, becoming pustular with a honey-colored crust within hours. When the vesicle breaks, a thick yellow crust forms from the exudate. Autoinoculation may cause satellite lesions. Other features include pruritus, burning, and regional lymphadenopathy.
A rare but serious complication of streptococcal impetigo is glomerulonephritis.
With bullous impetigo, a thin-walled vesicle opens and a thin, clear crust forms on the subsequent eruption. It commonly appears on exposed areas.

Introduction to Thiamine (Vitamin B1)

Thiamine (vitamin B1) provides the functional group for the coenzyme thiamine pyrophosphate, which is involved in decarboxylation of pyruvate and -ketoglutarate and, thus, is important in the release of energy from carbohydrates. It also participates in the hexose monophosphate shunt that generates nicotinamide adenine dinucleotide phosphate and pentose.

Thiamine also is required for the synthesis of acetylcholine, and deficiency results in impaired nerve conduction.

Good sources of thiamine include meat, legumes, and cereals. Unless enriched, refined cereals and flours have a much lower content of thiamine than whole grains. The vitamin is easily destroyed by heat, particularly in alkaline media, and significant amounts are lost in discarded cooking water. The breast milk of a well-nourished mother provides adequate thiamine; breast-fed infants of thiamine-deficient mothers, however, are at risk for deficiency. Most infants and older children obtain an adequate intake of thiamine from food and do not require supplements.

Thiamine is absorbed efficiently in the gastrointestinal tract, but may be decreased in persons with gastrointestinal or liver disease.

Deficiency (beriberi) has been reported in adolescents after gastric bypass surgery. Intakes in excess of tissue needs are excreted in the urine. Fever and/or stress may increase the requirement for thiamine and unmask marginal thiamine sufficiency, but these factors are unlikely to cause deficiency.

Hookworms Infection in Children

Two major genera of hookworms, which are nematodes or roundworms, infect humans. Necator americanus, the only representative of its genus, is a major anthropophilic hookworm and is the most common cause of human hookworm infection. Hookworms of the genus Ancylostoma includes the major anthropophilic hookworm Ancylostoma duodenale that also causes classic hookworm infection and the less common zoonotic species.

Life Cycle:
The infective larval stages of the anthropophilic hookworms live in a developmentally arrested state in warm, moist soil. Larvae infect humans either by penetrating through the skin (N. americanus and A. duodenale) or when they are ingested (A. duodenale). Larvae entering the human host by skin penetration undergo extraintestinal migration through the venous circulation and lungs before they are swallowed, whereas orally ingested larvae may undergo extraintestinal migration or remain in the gastrointestinal tract. Larvae returning to the small intestine undergo 2 molts to become adult sexually mature male and female worms ranging in length from 5 to 13 mm.

Epidemiology:
Hookworm infection is 1 of the most prevalent infectious diseases of humans, affecting an estimated 576 million individuals worldwide. Because of the requirement for adequate soil moisture, shade, and warmth, hookworm infection is usually confined to rural areas, especially where human feces are used for fertilizer or where sanitation is inadequate. Hookworm is an infection associated with economic underdevelopment and poverty throughout the tropics and subtropics. Sub-Saharan Africa, East Asia, and tropical regions of the Americas have the highest prevalence of hookworm infection.

Gonadal and Germ Cell Neoplasms in Children

Introduction

Malignant germ cell tumors (GCTs) and gonadal tumors are rare, with an incidence of 12 cases per million persons <20 yr of age. Most malignant tumors of the gonads in children are GCTs. The incidence varies according to age and sex.

Sacrococcygeal tumors occur predominantly in infant girls.

Testicular GCTs occur predominantly before age 4 yr and after puberty. Testicular GCTs occur much more often in whites than in blacks, whereas ovarian GCTs have a slight predominance in blacks.

Klinefelter syndrome is associated with an increased risk of mediastinal GCTs;

Down syndrome, undescended testes, infertility, testicular atrophy and inguinal hernias are associated with an increased risk of testicular cancer.

Clinical Manifestations And Diagnosis
The clinical presentation of germ cell neoplasms depends on location. Ovarian tumors often are quite large by the time they are diagnosed. Extragonadal GCTs occur in the midline, including the suprasellar region, pineal region, neck, mediastinum, and retroperitoneal and sacrococcygeal areas. Symptoms relate to mass effect, but the intracranial GCTs often present with anterior and posterior pituitary deficits.

The serum alpha-fetoprotein (AFP) level is elevated with endodermal sinus tumors and may be minimally elevated with teratomas. Infants have higher levels of AFP, which fall to normal adult levels by about 8 mo; therefore, high AFP levels must be interpreted with caution in this age group. Elevation of the Beta subunit of human chorionic gonadotropin (Beta-hCG) is seen with choriocarcinoma and germinomas. Lactate dehydrogenase (LDH), although nonspecific, may be a useful marker. If elevated, these markers provide important confirmation of the diagnosis and provide a means to monitor the patient for tumor response and recurrence. Both serum and cerebrospinal fluid should be assayed for these markers in patients with intracranial lesions.

Hereditary Predisposition to Thrombosis

Thromboses in children are frequently associated with a hereditary or acquired prothrombotic state. A significant number of hereditary causes of thrombosis are identified.

The newborn infant, because of the physiologic deficiency of various regulatory proteins, is particularly predisposed to both hemorrhage and thrombosis. For both anticoagulant proteins and most procoagulant factors, the more premature the infant, the greater the deficiency. The sick newborn infant is particularly at risk because interventions to provide support often include placement of large indwelling catheters into major veins or arteries. Those with hereditary deficiencies of anticoagulants may have major symptoms. After the neonatal period, young children seem to have some resistance to clinical thrombosis, even if they have a heterozygous hereditary deficiency of an anticoagulant protein. When a thrombus is identified in the young child, particularly when the family history is abnormal, a thrombotic evaluation should be initiated. In children and teenagers, thromboses are often triggered by major medical or surgical challenges.

Pathophysiology
A hereditary predisposition to thrombosis can be caused by deficiencies of the regulatory proteins protein C, protein S, antithrombin III, and plasminogen; synthesis of a procoagulant protein unable to be inhibited by its regulatory protein, factor V Leiden; elevated levels of procoagulant protein; prothrombin mutation (G20210A); and elevated levels of a toxic organic acid, homocystinemia.