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Patient Story

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A 9-year-old boy from rural Asia was brought to the clinic by his parents for complaints of being tired and “blue.” Further history reveals that he has had frequent episodes of squatting after exertion which relieves some of the symptoms temporarily. On exam, he has clubbing of the fingers and toes with cyanosis of the lips and oral mucous membranes (Figure 41-1). A harsh systolic ejection murmur is best heard at the left mid and upper sternal border. An echocardiogram confirms the diagnosis of tetralogy of Fallot.

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FIGURE 41-1

Central cyanosis of the lips in this 9-year-old boy with unrepaired Tetralogy of Fallot. (Used with permission from Athar M. Qureshi, MD.)

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Introduction

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Clubbing is the enlargement of the distal fingers or toes along with the formation of convex shaped fingernails or toenails.

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Cyanosis is the bluish discoloration of the skin or mucous membranes due to increased quantity of deoxyhemoglobin in the blood. Unless otherwise specified, cyanosis in this chapter refers to central cyanosis.

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Synonyms

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  • Clubbing: Hypertrophic osteoarthropathy.

  • Cyanosis: Central cyanosis or hypoxemia.

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Epidemiology

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  • Clubbing and cyanosis are disease manifestations seen worldwide and their incidence is difficult to discern.

  • Chronic cyanosis as a result of unrepaired congenital heart disease is seen mainly in developing nations.

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Etiology and Pathophysiology

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  • The exact etiology of clubbing is unknown. However, it has been hypothesized that it may result from megakaryocytes that have bypassed the pulmonary vascular bed and entered the systemic circulation or from platelet clumps that form and/or enter the systemic circulation. They then release platelet-derived growth factor causing clubbing.1,2

  • A right to left cardiac shunt or significant lung disease easily allows platelets to bypass the lungs and hence cause clubbing. Conditions that result in platelet excess, that is, inflammatory bowel disease, may also result in clubbing.

  • Cyanosis occurs due to reduced capillary blood oxygen saturation and becomes apparent when deoxyhemoglobin in the blood exceeds a value of 3 to 5 g/dL (corresponding arterial saturations of 70 to 85 percent).3

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Risk Factors

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Clubbing
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  • Lung disease including chronic infections or malignancies.

  • Cyanotic congenital heart disease (most common cause in children), endocarditis.

  • Chronic gastrointestinal disorders, i.e., inflammatory bowel disease, liver cirrhosis.

  • Hereditary.

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Cyanosis
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  • Cyanotic heart disease.

  • Lung disorders.

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Diagnosis

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Clinical Features
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Clubbing
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  • Fluctuation and softening of the nail bed can be appreciated early. Enlargement of the distal segments of affected extremities that is usually painless develops (Figures 41-2 and Figure 41-3).

  • Reduction in the angle between the nail ...

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