The bulbous digital deformity known as clubbing (Figure 2.1a,b) was described as early

as the fifth century BC when Hippocrates noted such changes in patients suffering from

empyema. The diagnostic signs comprise:

1 Overcurvature of the nails in the proximal to distal and transverse planes (Figure

2.2).

2 Enlargement of periungual soft tissue structures confined to the tip of each digit.

A simple method to detect clubbing is measurement of the phalangeal depth ratio (Figure

2.3). In a normal finger the distal phalangeal depth is smaller than the interphalangeal

depth. In clubbing this relationship is reversed (>1). The measurement can easily be taken

using a caliper in less than a minute.

Figure 2.1

(a, b) Clubbing.

Figure 2.2

Clubbing, demonstrating typical nail curvature and obliteration of the

‘window’.

Figure 2.3 In clubbing the phalangeal depth ratio is greater than

1. (a/b>1)

The increased nail curvature usually affects all 20 digits, but may be particularly

obvious on the thumbs, index and middle fingers. The ‘watch-glass’ shape of the nail

may occur as an isolated deformity without any associated enlargement of the tip of the

digit. The shape of the curved nails is variable and may appear fusiform, like a bird’s

beak, or clubbed like a watch-glass. The matrix quite often appears abnormally large.

There are three main types of clubbing:

1 Simple clubbing.

2 Hypertrophic pulmonary osteoarthropathy.

3 Pachydermoperiostosis.

Simple clubbing

Simple clubbing is the most common category and has several distinctive characteristics:

1 Increased nail curvature occurs with a transverse furrow separating it from the rest

of the nail both in the early stage and after resolution. The onset is usually gradual

and painless, except in some cases of carcinoma of the lung in which clubbing may

develop abruptly and be associated with severe pain.

2 Hypertrophy of the soft parts of the terminal segment caused by firm, elastic,

oedematous infiltration of the pulp, which may spread to the dorsal surface with

marked periungual swelling.

3 Hyperplasia of the dermal fibrovascular tissue may extend to involve the adjacent

matrix. This accounts for one of the earliest signs of clubbing—abnormal mobility

of the nail base, which can be rocked back and forth giving the impression that it is

floating on a soft oedematous pad. The increased vascularity is responsible for the

slow return of colour when the nail is pressed and released.

4 Acral cyanosis is often observed.

In the early stages clubbing may involve one hand only, though eventually both hands

become affected symmetrically. Several stages of clubbing or acropachy may be

distinguished: suspected, slight, average and severe. In practice the degree of the

deformity may be gauged by Lovibond’s ‘profile sign’ which measures the angle between

the curved nail plate and the proximal nail fold when the finger is viewed from the radial

aspect. This is normally 160°, but exceeds 180° in clubbing. A modified profile sign is

assessed by measuring the angle between the middle and the terminal phalanx at the

interphalangeal joint: in normal fingers the distal phalanx forms an almost straight (180°)

extension of the middle phalanx, whereas in severe clubbing this angle may be reduced to

160° or even 140°. However, the best indicator may be the simple clinical method

adopted by Schamroth: in normal individuals a distinct aperture or ‘window’, usually

diamond-shaped, is formed at the base of the nail bed; early clubbing obliterates this

window. (Fig 2.2).

Radiological changes occur in less than one-fifth of cases. These include phalangeal

demineralization and irregular thickening of the cortical diaphysis. Ungual tufts generally

show considerable variations and may be prominent in advanced stages of the disease.

Bony atrophy may be present.

Congenital finger clubbing may be accompanied by changes such as hyperkeratosis of

the palms and soles, and cortical hypertrophy of the long bones. Familial clubbing may

be associated with hypertrophic osteoarthropathy; some authors regard simple clubbing

as a mild form of the latter. Isolated watch-glass nails without other deformities are also

constitutionally determined. Rare cases of unilateral Hippocratic nails have been reported

due to obstructed circulation, oedema of the soft tissues and dystrophy of the affected

parts. The pathological process apparently responsible for clubbing and its associated

changes is the increased blood flow due to the opening of many anastomotic shunts.

Hypertrophic pulmonary osteoarthropathy

This disorder is characterized by the following five signs:

1 Clubbing of the nails.

2 Hypertrophy of the upper and lower extremities similar to the deformity found in

acromegaly.

3 Joint changes with pseudo-inflammatory, symmetrical, painful arthropathy of the

large limb joints, especially those of the legs. This syndrome is almost

pathognomonic of malignant chest tumours, especially lung carcinoma and

mesothelioma of the pleura; less commonly bronchiectasis is seen. Gynaecomastia

may also be present.

4 There may be bone changes such as bilateral, proliferative periostitis and moderate,

diffuse decalcification.

5 Peripheral neurovascular disorders such as local cyanosis and paraesthesia are not

uncommon.

Hypertrophic osteoarthropathy confined to the lower extremities appears as a

manifestation of arterial graft sepsis.

Pachydermoperiostosis

Pachydermoperiostosis (idiopathic hypertrophic osteoarthropathy) is rare. In most of the

reported cases the digital changes typically begin at or about the time of puberty. The

ends of the fingers and toes are bulbous and often grotesquely shaped, with hyperhidrosis

of the hands and the feet (Figure 2.4). The clubbing stops abruptly at the distal

interphalangeal joint. In this type the lesions of the finger tips are clinically identical to

those of hypertrophic pulmonary osteoarthropathy. However, in pachydermoperiostosis

the thickened cortex appears homogeneous on X-ray examination and does not impinge

on the medullary space. Acro-osteolysis of the distal phalanges has been reported.

Figure 2.4

Clubbing in pachydermoperiostosis.

The pachydermal change of the extremities and face, with furrowing and oiliness of the

skin, is the most characteristic feature of the disorder; it is termed the Touraine-Solente-

Golé syndrome. Nevertheless, in hypertrophic pulmonary osteoarthropathy there may be

facial    skin    and    scalp    changes    indistinguishable    from those    seen in

pachydermoperiostosis; this may be due to a common genetic factor. In the differential

diagnosis acromegaly must be considered; this enhances tufting of the terminal phalanges

and presents an anchor-like appearance, but without acro-osteolysis. Thyroid acropachy

is usually associated with exophthalmos, pretibial myxoedema and abnormal thyroid

function.

It should be noted that only rarely will any type of clubbing present to a dermatologist,

since in most cases it is simply one sign among many relating to the primary cause.

Classification of clubbing

The principal general causes of clubbing are listed in Table 2.1; a more comprehensive

list of causes is given below.

Idiopathic forms

Hereditary and congenital forms, sometimes associated with other anomalies:

• familial and genotypic pachydermoperiostosis

• racial forms (Africans)

• syndrome of pernio, periostosis and lipodystrophy

• Muckle-Wells syndrome.

Acquired forms

1 Thoracic disorders are involved in about 80% of cases of clubbing, often with the

common denominator of hypoxia:

• bronchopulmonary diseases, especially chronic and infective bronchiectasis,

abscess and cyst of the lung, pulmonary tuberculosis

• sarcoidosis, pulmonary fibrosis, emphysema, Ayerza’s syndrome, chronic

pulmonary venous engorgement, asthma in infancy, mucoviscidosis

• blastomycosis, pneumonia, Pneumocystis carinii infection, AIDS.

2 Thoracic tumours:

• primary or metastatic bronchopulmonary cancers, pleural tumours, mediastinal

tumours

• Hodgkin’s disease, lymphoma, pseudotumour due to oesophageal dilatation.

Figure 2.5

Pseudoclubbing due to trauma—hooked nail deformity.

3 Cardiovascular disease:

• congenital heart disease associated with cyanosis (rarely non-cyanotic)

• thoracic vascular malformations; stenoses and arteriovenous aneurysms

• Osler’s disease (subacute bacterial endocarditis)

• congestive cardiac failure

• myxoma

• Raynaud’s disease, erythromelalgia, Maffucci’s syndrome.

4 Disorders of the alimentary tract (5% of cases):

• oesophageal, gastric and colonic cance

• disease of the small intestine

Figure 2.6

Clubbed appearance in acromegaly. (Courtesy of D.Wendling.)

Figure 2.7

Pseudoclubbing in yellow nail syndrome.

• colonic disease

• amoebiasis and inflammatory states of the colon

• ulcerative colitis

• familial polyposis, Gardner’s syndrome

• ascariasis

• active chronic hepatitis

• primary or secondary cirrhoses

• purgative abuse.

5 Endocrine origin:

• Diamond’s syndrome (pretibial myxoedema, exophthalmos and finger

clubbing)

• acromegaly.

6 Haematological causes:

• methaemoglobinaemia

• sulphaemoglobinaemia

• haemoglobinopathies

• primary or secondary polycythaemia associated with hypoxia

• poisoning by phosphorus, arsenic, alcohol, mercury or beryllium.

7 Hypervitaminosis A.

8 Malnutrition, kwashiorkor.

9 Addiction (hashish, heroin).

10 Syringomyelia, POEMs syndrome (peripheral neuropathy, organomegaly,

endocrinopathy, monoclonal plasmaproliferative disease, skin changes).

11 Lupus erythematosus.

12 Unilateral or limited to a few digits:

• subluxation of the shoulder (with paralysis of the brachial plexus), medial nerve

neuritis

• Pancoast-Tobias syndrome

• aneurysm of the aorta or the subclavian artery

• sarcoidosis

• tophaceous gout.

13 Lower extremities:

• arterial graft sepsis.

14 Isolated forms:

• local injury, whitlow, lymphangitis

• subungual epidermoid inclusions.

15 Transitory form: physiological in the newborn child (due to reversal of the

circulation at birth).

16 Occupational acro-osteolysis (exposure to vinyl chloride).