Diagnosis of polyarteritis nodosa

Diagnosis of polyarteritis nodosa is often difficult due to the non-specificity of the initial symptoms, polymorphism of clinical manifestations, and the absence of specific laboratory markers. The basis for diagnosis is primarily the clinical picture, which becomes apparent during the first 3 months of the disease. When establishing a diagnosis, specific clinical syndromes (the main diagnostic criteria) are taken into account. Of auxiliary importance are such signs as increased body temperature, weight loss, joint and muscle pain, leukocytosis, increased ESR, and markers of viral hepatitis B.

Classification criteria for polyarteritis nodosa in children (here and below the criteria are arranged according to specificity and sensitivity from the highest to the lowest percentage)

Criteria	Clarification
Main
Multiple asymmetric mononeuritis or asymmetric polyneuritis	Combined or sequential damage to the radial, ulnar, median, peroneal and other nerves
Ischemic bowel disease	Infarction, necrosis of the intestinal wall with single or multiple lesions
Arterial hypertension syndrome	Persistent increase in diastolic pressure in combination with urinary syndrome and, possibly, markers of hepatitis B
Characteristic angiographic changes	Aneurysms of small and medium intraorgan arteries in combination with focal vascular deformation (hepatic, renal and other arteries)
Necrotizing vasculitis (based on biopsy)	Destructive-proliferative vasculitis of small and medium arteries of muscular type, revealed by biopsy
Auxiliary
Pain in joints and/or muscles	Persistent pain, causalgia of large joints and muscles of the distal extremities
Fever	An increase in body temperature above 38 'C daily or episodic with profuse sweating for 2 weeks or more
Leukocytosis of peripheral blood	Leukocytosis more than 20.0x109/l, determined in three consecutive analyses
Weight loss	A decrease in body weight of more than 15% of the initial weight in a short period of time, not associated with fasting

The diagnosis of polyarteritis nodosa is established in the presence of at least two main criteria or one main and three auxiliary criteria.

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Laboratory diagnostics of polyarteritis nodosa

In the active period of polyarteritis nodosa, a general blood test reveals moderate normochromic anemia, neutrophilic leukocytosis, and an increase in ESR.

A general urine analysis may reveal transient changes in sediment.

Biochemical blood analysis has practical value, revealing changes in certain indicators, in particular transferase activity and nitrogenous wastes.

During an immunological study during the active period, all patients show an increase in the concentration of C-reactive protein; a moderate increase in IgA, IgG, and a positive rheumatoid factor can be detected.

The blood coagulation system in nodular polyarteritis is characterized by a tendency to hypercoagulation, therefore, the determination of the state of hemostasis should be initial and subsequent to control the adequacy of therapy. Hypercoagulation is most pronounced in juvenile polyarteritis.

In patients with classic polyarteritis nodosa, HBsAg and other markers of hepatitis B are detected (without clinical, laboratory and epidemiological signs of this disease).

Instrumental diagnostics of polyarteritis nodosa

According to indications, ECG, echocardiography, chest X-ray, ultrasound of abdominal organs, angiography, and biopsy are prescribed.

ECG can reveal signs of metabolic disturbances in the myocardium, tachycardia. In the presence of myocarditis, conduction slowing, extrasystole, and decreased electrical activity of the myocardium can be recorded. In case of damage to the coronary arteries, ischemic changes in the heart muscle are revealed.

In case of myocarditis, echocardiography reveals dilation of the heart cavities, thickening and/or hyperechogenicity of the walls and/or papillary muscles, decreased contractile and pumping functions of the myocardium, and in the presence of pericarditis, stratification or thickening of the pericardial layers.

During ultrasound examination of the abdominal organs and kidneys, non-specific changes are most often noted in the form of increased vascular pattern and/or echogenicity of the parenchyma.

On a chest X-ray during the active period of the disease, an increase in the vascular pattern is noted, and sometimes a change in the pulmonary interstitium.

Aortography is prescribed for nodular polyarteritis occurring with arterial hypertension, for diagnostic and differential diagnostic purposes. Angiograms can reveal aneurysms of medium and small vessels of the kidneys, liver, spleen and defects in contrasting the parenchyma of the affected organs, which serves as an angiographic criterion for the disease.

Biopsy of the skin, subcutaneous tissue and muscles, rarely - the kidney, is performed in doubtful cases. It is advisable to perform a biopsy before the start of basic therapy. The morphological sign confirming the diagnosis of nodular polyarteritis is destructive-productive vasculitis, which can be detected only if the biopsy is performed from a skin area with a nodule, livedo or near necrosis.

Classification criteria for juvenile polyarteritis

Criteria	Clarification
Main
Gangrene of fingers and/or skin necrosis	Acute development of dry asymmetric gangrene involving I-III fingers, mummification of skin areas
Nodular eruptions	Intradermal or subcutaneous nodules up to 1 cm in diameter along the course of blood vessels
Tongue infarction	Painful wedge-shaped cyanosis of the tongue with development of necrosis
Livedo arborescens	Cyanotic coarse-meshed network on distal extremities, worse in cold and standing
Auxiliary
Necrotizing vasculitis (based on biopsy)	Destructive-proliferative vasculitis of small and medium arteries of muscular type, revealed by biopsy
Weight loss	A decrease in body weight of more than 15% of the initial weight in a short period of time, not associated with fasting
Pain in joints and/or muscles	Persistent pain, causalgia of large joints and muscles of the distal extremities
Fever	An increase in body temperature above 38 C daily or episodic with profuse sweating for 2 weeks or more
Leukocytosis of peripheral blood	Leukocytosis more than 20.0x10 9 /l, determined in three consecutive analyses

The diagnosis of juvenile polyarteritis is established in the presence of at least three main or two main and three auxiliary criteria.

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Differential diagnosis of polyarteritis nodosa

In the acute onset of juvenile polyarteritis with high body temperature, joint and muscle pain, skin rashes, hepatomegaly, there is often a need for differential diagnosis with sepsis, juvenile rheumatoid arthritis, juvenile dermatomyositis, systemic lupus erythematosus, Kawasaki syndrome, nonspecific aortoarteritis.

When conducting differential diagnostics, it should be understood that nodular polyarteritis is not characterized by destructive arthritis characteristic of juvenile rheumatoid arthritis, in contrast to juvenile dermatomyositis, juvenile polyarteritis does not have such a pronounced muscle weakness syndrome, livedo and skin necrosis are located mainly on the distal parts of the limbs, periorbital lilac erythema is not observed. Unlike systemic lupus erythematosus, patients with juvenile polyarteritis more often have dendritic rather than reticular livedo, distal gangrene, hyperleukocytosis. Nodular polyarteritis is not characterized by endocarditis, polyserositis and nephrotic syndrome, LE cells are not determined in it.

Differential diagnosis of polyarteritis nodosa is complicated by sudden onset of high blood pressure in a child. In such cases, the diagnosis of polyarteritis nodosa often has to be established by exclusion, consistently rejecting the assumption of pheochromocytoma, renal artery stenosis, pyelonephritis with an outcome in nephrosclerosis, chronic glomerulonephritis. The following testifies in favor of polyarteritis nodosa: persistent high blood pressure, combined with signs of systemic vascular damage, fever, increased ESR and leukocytosis, HBs antigenemia (without clinical hepatitis).

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