Index of Suspicion
1997; American Academy of Pediatrics; Volume: 18; Issue: 4 Linguagem: Inglês
10.1542/pir.18-4-137
ISSN1529-7233
AutoresThomas C. Bisett, Sol Rockenmacher, Isabelle G. De Plaen, Maryann Buetti-Sgouros,
ResumoA 16-year-old girl who has Down syndrome is evaluated by a pediatric cardiologist because of a recently noted heart murmur. Eight years ago, another murmur was heard that sounded innocent and eventually disappeared. Results of electrocardiography (EKG) and chest radiography at that time were normal.Although a participant in the Special Olympics,this girl is not an active person; her mother is concerned that she has gained too much weight in the last year. Findings on physical examination include a weight of 128 lb (75th percentile on Down syndrome growth chart;was 50th at last examination 3 years ago) and a height of 56 in (40th percentile; was 75th). Her blood pressure is 90/60 mm Hg, her pulse 52 beats/ min, she is Tanner stage 5 in breast maturity, and her face is mildly puffy. Her lungs are clear. Cardiac findings include a normal apical impulse,heart sounds of normal intensity with a split second sound that closes on expiration, and peripheral pulses of normal amplitude. A grade I/VI systolic ejection murmur is audible along the left sternal border, radiating across the precordium. No neck masses, neck vein distension, or hepatomegaly are noted.Results of an EKG show sinus bradycardia, borderline low voltage,and nonspecific T-wave flattening. A chest radiograph shows normal heart size and pulmonary vascular markings. A limited echocardiogram reveals a significant abnormality. Blood chemistries are ordered that explain her clinical findings.A 4-day-old boy is brought to the emergency department because of anuria and vomiting. Born vaginally after an uneventful pregnancy, the baby was discharged from the nursery at 24 hours of age but developed increasingly severe nonbilious vomiting. He had passed meconium on the first day of life and a dark stool yesterday. He wet several diapers earlier, but his urine output has decreased. His family history reveals a maternal uncle who had a congenital hydronephrosis.On physical examination the infant appears comfortable and in no distress. He has a respiratory rate of 50 breaths/ min, heart rate of 156 beats/min,blood pressure of 75/59 mm Hg, and temperature of 36.6°C. He weighs 2,880 g (430 g below his birthweight). The baby is mildly jaundiced. His abdomen is soft, and bowel sounds are present; no hepatosplenomegaly is noted. The remainder of the physical examination is normal.Blood chemistry values are as follows: sodium, 143 mEq/L; potassium, 7 mEq/L; ionized calcium, 0.82 mEq/L; phosphate, 14 mEq/L; magnesium, 2 mg/dL;blood urea nitrogen, 36 mg/dL; and creatinine, 3.2 mg/dL. Catheterization of the bladder results in a small amount of urine, which reveals: specific gravity, 1.015; pH, 8.5; and no protein. Microscopic examination shows 2 to 3 erythrocytes, 5 to 8 white blood cells, and 1 to 2 finely granular casts per high-power field. The baby’s urinary sodium is 70 mEq/L; potassium, 53.5 mEq/L; chloride, 31 mEq/L; and creatinine, 49 mg/dL. Results of renal ultrasonography are normal.A simple radiographic procedure leads to the correct diagnosis.An 11-year-old Asian girl comes to the emergency department because of visual loss. Two months ago she was seen at another hospital because of a painful stiff neck with worsening pain on rotation of her head to the left. Radiographs of her cervical spine were normal, and she was discharged with a diagnosis of muscle spasm, for which ibuprofen was recommended. Subsequently,she experienced gradual changes in her vision but did not mention the problem until several days ago, when she noticed that she no longer could read her homework because her vision was blurry.Her history includes noncompliance in wearing glasses prescribed at age 5 years. The patient’s mother feels that she has not gained weight properly, and friends have noticed that she seems apathetic.This thin girl appears in no distress. Her temperature, pulse rate, blood pressure, and respiratory rate are normal. She is at Tanner stage 1 of sexual maturity. Her pupils are equal, round, and reactive to light, and her extra-ocular movements are intact. She has incomplete convergence and a slight ptosis of her left eye. Her visual acuity is 20/80 in each eye, and there is a subtle visual field defect in the upper and nasal quadrants of both eyes. Her optic disc margins are indistinct. The remainder of her cranial nerve functions are normal. She has normal muscle tone, and symmetric, 2+ deep tendon reflexes. Her neck is supple without pain on movement, deformity, or palpable thyroid. Results of the examination of her head, back, heart, lungs,and abdomen are normal.A thorough skin examination and one radiologic study confirm the diagnosis.A limited echocardiogram on this patient demonstrated a moderate pericardial effusion but no evidence of cardiac tamponade. Her thyroid function tests revealed a free thyroxine (T4) level of less than 0.4 ng/dL(normal range, 0.7 to 1.9 ng/dL), a triiodothyronine (T3) level of 66 ng/dL(normal range, 80 to 22 ng/dL), and a thyroid stimulating hormone (TSH) level of 168 μIU/mL (normal range, 0 to 5.5 μIU/mL). Antithyroid peroxidase,antithyroglobulin, and antithyroid microsomal antibody determinations all were negative. A complete echocardiogram showed no structural abnormality. Her pericardial effusion was a result of hypothyroidism, and therapy was started with l-thyroxine.Down syndrome is associated with both congenital and acquired hypothyroidism. Pericardial effusion may be the presenting clinical problem in both situations. Congenital hypothyroidism is approximately 28 times more common in infants who have Down syndrome than in the general population. The cause of the thyroid failure in these patients is unknown; it does not appear to be caused by autoimmune disease, and most patients have a normal thyroid scan, which excludes the possibility of ectopic glands or athyreosis.After the newborn period, the prevalence of thyroid disease in individuals who have Down syndrome is about 3%, which is appreciably higher than that seen in the general population. Evidence of autoimmune disease frequently is detectable in these patients. When T3 and T4 levels are tracked over the first 3 decades of life in longitudinal studies, people who have Down syndrome show significantly greater declines than do control populations.Acquired hypothyroidism is associated with a number of clinical signs, the most important being growth failure. Constipation, low body temperature, and myxedema can occur. Physical activity may slow, and mental capacities may be impaired. The clinical picture can be subtle and easy to overlook. Many people who have Down syndrome tend to be relatively inactive and are heavy, as well as developmentally delayed, making the detection of hypothyroidism even more difficult. As demonstrated by this patient, the significance of the anthropomorphic data that suggest thyroid dysfunction—growth delay and excessive weight gain—could have been less apparent if changes in her growth pattern had not been recognized and if growth charts specific for individuals who have Down syndrome had not been used. The American Academy of Pediatrics (AAP) recommends that thyroid function tests be performed periodically in patients who have Down syndrome.Pericardial effusion can be demonstrated by echocardiogram in about 50% of infants and 75% of children who have hypothyroidism. The effusion usually is asymptomatic and rarely leads to cardiac tamponade. When the diagnosis of hypothyroidism is delayed, as it may be in patients who have Down syndrome, very large effusions may develop.Use of appropriate growth charts and regular monitoring of thyroid function may allow earlier diagnosis and prevention of effusions as well as other effects of hypothyroidism.An abdominal radiograph revealed a “double-bubble” sign and the absence of bowel gas—hallmark findings of complete duodenal obstruction. This baby was anuric on arrival and underwent aggressive rehydration. His urine output, serum electrolyte levels, and renal function normalized rapidly over fewer than 48 hours. A duodenostomy was performed subsequently, and the baby did well. Although the child had experienced some minor regurgitation before discharge, its significance was not apparent. Had he not been discharged at 24 hours of age but allowed to stay longer, it is likely that the diagnosis would have been made sooner and subsequent renal problems avoided.Duodenal atresia occurs in 1 of every 10,000 births. In 70% to 85% of cases, the atresia is located in the second or third portion of the duodenum, distal to the ampulla of Vater. Infants who have this anomaly usually present with polyhydramnios and bilious vomiting that starts shortly after birth. The presence of bilious secretion in the amniotic fluid often is mistaken for meconium. In 15% to 30% of cases, the atresia is proximal to the ampulla of Vater, and neonates present with nonbilious vomiting and dark stools, as in this case.Three types of duodenal atresia have been described. Type 1 takes the form of an intact membrane of mucosa and submucosa. Type 2 consists of a short fibrous cord connecting two blind ends of duodenum. In type 3, a gap exists between blind duodenal ends. The defect is thought to be caused by a failure of recanalization of the duodenal lumen, which begins between 8 and 10 weeks of gestation. Atresias of the jejunum and ileum are caused by intrauterine vascular anomalies or accidents that occur later in pregnancy than the events leading to duodenal atresia.Of all patients who have duodenal atresia, 10% to 30% also have Down syndrome. Other congenital anomalies frequently associated with duodenal atresia are esophageal atresia, malrotation, congenital heart disease, and anorectal malformations. Jejunal and ileal atresias usually are not associated with other anomalies.The abdomen of an infant who has duodenal atresia usually is scaphoid with localized epigastric distention caused by a dilated stomach. Many conditions will cause significant vomiting in a newborn baby, including a number of disorders that cause obstruction. Certain clinical findings will help the clinician to localize an obstruction. Nonbilious vomiting indicates an obstruction proximal to the ampulla of Vater, as in this infant, whereas the presence of bile points to a more distal obstruction. When the obstructed area is in the ileum, jejunum, or colon, abdominal distention occurs, in contrast to a scaphoid abdomen. Delay in the passage of stool beyond 48 hours suggests a lesion in the distal small intestine or colon; however, the passing of meconium does not rule out a complete intestinal obstruction.Plain radiographs of the abdomen can be helpful in many ways, such as by indicating the extent to which the intestinal tract is filled with air. Sometimes a specific pattern can lead to a diagnosis. The “double-bubble” sign associated with duodenal atresia is caused by air-fluid levels in the gastric antrum and the duodenum.Another cause of congenital duodenal obstruction, which is less common than duodenal atresia, is compression of the second portion of the duodenum by an annular pancreas (associated with other anomalies in 70% of cases), a preduodenal portal vein, a mesenteric band, or a malrotation of the gut with volvulus. In patients who have findings of duodenal obstruction, it is extremely important to rule out malrotation with midgut volvulus. In as many as 50% of these cases, the physical examination is normal. Other patients present with distention, abdominal tenderness, or signs of peritonitis and shock. If the patient has malrotation, an upper gastrointestinal series will show that the duodenojejunal junction is located to the left of the spine. A barium enema may identify an abnormally positioned cecum. In 5% to 20% of patients who have malrotation, however, the cecum is in a normal position. Ultrasonographic examination by an experienced radiologist sometimes is helpful in identifying an inversion of the mesenteric artery and vein. Malrotation with volvulus must be considered to be present until proven otherwise because it requires immediate surgical correction.The infant who has duodenal atresia should have a nasogastric tube placed and be given nothing by mouth. Intravenous fluids should be administered. Once the diagnosis of malrotation with midgut volvulus has been ruled out,dehydration and electrolyte abnormalities should be corrected prior to surgery.If duodenal atresia is not diagnosed rapidly, the patient will develop hypo-chloremic metabolic alkalosis because of the emesis of gastric secretions and hypokalemia from the shift of potassium ions into cells as a response to the alkalosis. Another reason to defer surgery until correction of electrolyte disturbances is that the hyperventilation associated with intubation and anesthesia can aggravate the alkalosis acutely, worsening hypokalemia and inducing hypocalcemia, which can lead to arrhythmias. Advanced degrees of dehydration can lead to prerenal failure and subsequent hyperkalemia, which can be a misleading sign in the presentation of duodenal atresia.A challenging feature of this infant’s clinical course was his renal involvement. He had a blood urea nitrogen/creatinine ratio of 11.25 and a fractional excretion of sodium of 3.2% ( 2.5% in intrinsic renal failure), both of which would suggest intrinsic renal failure. His physicians were faced with a dilemma: a dehydrated baby who has prerenal failure requires aggressive fluid therapy, whereas one who has true intrinsic renal failure could be seriously harmed by fluid overloading if too much were given. The fact that this patient had lost considerable weight was informative. In any case, it is safe to give one initial bolus of 20 mL/kg of intravenous fluid and monitor the patient for response. Clinical improvement and the passage of urine will indicate the safety of administering more fluid. The normalization of this baby’s renal function and electrolytes over the next 2 days indicated that most of his problem was prerenal, although a literal interpretation of the indices raises the question of whether he had sustained some renal damage. The important lesson is that one must interpret indices of renal function with great care in newborns.A complete skin examination revealed inguinal freckling and numerous café-au-lait spots—some as large as 5 cm—on the backs of this girl’s legs. A computed tomographic scan of her head revealed a large suprasellar mass at the area of the optic chiasm. These findings confirmed the diagnosis of neurofibromatosis type 1 (NF-1). The child was admitted for removal of the brain mass, which was found on pathologic examination to be a juvenile pilocytic astrocytoma. The cause of her initial neck complaints was not evident; they may have been related to unnatural positioning of her head in an attempt to compensate for the visual changes.The complaint of visual loss in a child always should be taken seriously. The differential diagnosis includes diseases that involve the eye, such as iritis or retinal detachment, as well as conditions of the central nervous system, such as basilar migraine, disease of the occipital lobe, or tumor of the optic chiasm, as in this girl.Neurofibromatosis is one of several disorders known as phakomatoses, which are characterized by their tendency to cause neurocutaneous lesions. There are at least eight forms of the disease. The most common is NF-1, which accounts for 80% of cases. The prevalence of NF-1 is about 1 in 3,000 in the general population. It is inherited in an autosomal dominant fashion, although as many as 50% of patients may have developed the disorder through a spontaneous mutation. Although its penetrance is virtually 100%,patients who have NF-1 can present with a broad spectrum of symptoms, from very mild disease that primarily involves skin lesions to severe disease that involves the development of both neurofibromas in vital organs and malignant tumors.The gene for NF-1 has been localized on chromosome 17. It is believed that the gene normally encodes for a tumor suppressor; hence, mutations in its sequence are believed to lead to the increased incidence of malignant tumors associated with the disorder. Among the tumors that occur with increased frequency in patients who have NF-1 are optic gliomas, astrocytomas,malignant peripheral nerve sheath tumors, several forms of leukemia, and rhabdomyosarcoma.The diagnostic features of NF-1 are as follows, with the presence of two or more necessary to make the diagnosis: Many of these lesions develop subtly, with periods of rapid growth in adolescence and during pregnancy.The presentation of NF-1 is highly variable. The presence of café-au-lait spots is one of the most common signs. These well-circumscribed, light brown macules are found in 10% of all individuals and often are not a sign of any other disorder. The presence of six or more of these lesions,however, should raise the suspicion of NF-1 and prompt further investigation. It must be noted that café-au-lait spots also are associated with other disorders, including ataxia telangiectasia, tuberous sclerosis, Albright syndrome, Bloom syndrome, Russell-Silver syndrome, multiple lentigines,Fanconi anemia, and Turner syndrome.NF-1 produces lesions that affect many organ systems. Hypertension resulting from renal artery stenosis or pheochromocytoma and scoliosis caused by tumors or bony abnormalities are among the presenting signs that lead to further evaluation. Because the pathologic lesions often evolve slowly, with the development of neurofibromas occurring predominantly after the onset of puberty, clinicians should screen patients closely who have a lesion suggestive of neurofibromatosis. Other lesions that should heighten the suspicion of NF-1 include tibial pseudarthrosis (often recognized when the child begins to bear weight), sphenoid wing dysplasia, and optic pathway gliomas.Because NF-1 is a progressive disease, the use of screening techniques at various times during the patient’s development may help to detect lesions before they become symptomatic. The AAP’s Committee on Genetics has made recommendations for screening patients who have NF that include the following: Because there is no cure for neurofibromatosis, screening of patients for developing tumors may lead to early intervention and symptomatic relief.
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