Scleroderma and kidney damage - Diagnosis

Laboratory diagnostics of scleroderma and kidney damage

Laboratory examination of patients with systemic scleroderma may reveal anemia, moderate increase in ESR, leukocytosis or leukopenia, hyperproteinemia with hypergammaglobulinemia, elevated levels of C-reactive protein and fibrinogen. Immunological examination reveals antinuclear factor (in 80% of patients), rheumatoid factor (mainly in patients with Sjögren's syndrome) and specific antinuclear "scleroderma" antibodies. These include:

• antitopoisomerase (previous name - aHTH-Scl-70), detected mainly in the diffuse cutaneous form of systemic scleroderma;
• anticentromere - in 70-80% of patients with a limited form of systemic scleroderma;
• anti-RNA polymerase - associated with a high incidence of kidney damage.

Scleroderma nephropathy is characterized by an increase in plasma renin levels, which in some cases is detected even in patients with mild arterial hypertension or normal arterial pressure. In 30% of patients with true scleroderma nephropathy, microangiopathic hemolytic anemia develops, which can be diagnosed based on a sudden sharp decrease in hemoglobin and hematocrit levels, reticulocytosis, an increase in the concentration of bilirubin and lactate dehydrogenase (LDH) in the blood serum, and the detection of schistocytes in a peripheral blood smear.

Instrumental diagnostics of scleroderma and kidney damage

To diagnose microcirculatory vascular damage in systemic scleroderma, the method of wide-field capillaroscopy of the nail bed is used, which allows one to identify the expansion and tortuosity of capillary loops, reduction of the capillary network (reduction in the number of capillaries, “avascular fields”).

A modern non-invasive method of ultrasound Dopplerography of intrarenal arteries allows for the assessment of the state of renal blood flow, with the help of which it is possible to identify disorders even before the development of clinical manifestations of scleroderma nephropathy.

Differential diagnosis of scleroderma

In diagnosing systemic scleroderma, the clinical symptoms of the disease are of decisive importance. The American Rheumatology Association has proposed simple diagnostic criteria for systemic scleroderma, including:

• "big" criteria:
  • proximal scleroderma - scleroderma lesion of the skin proximal to the metacarpophalangeal joints, spreading to the chest, neck and face;
• "minor criteria":
  • sclerodactyly;
  • digital ulcers or scars on the palmar surface of the nail phalanges of the fingers;
  • bilateral basal pulmonary fibrosis.

Diagnosis of scleroderma is based on a combination of major and at least two minor criteria. The appearance of signs of kidney damage in patients with an established diagnosis of systemic scleroderma indicates the development of scleroderma nephropathy. The diagnosis of true scleroderma kidney is beyond doubt in the development of acute renal failure combined with severe or malignant arterial hypertension in patients with systemic scleroderma. However, the same clinical picture that developed at the onset of the disease, even before the verification of the diagnosis of systemic scleroderma, presents significant diagnostic difficulties. In this situation, the characteristic triad of early signs of systemic scleroderma can help clarify the diagnosis: Raynaud's syndrome, articular syndrome (usually polyarthralgia) and dense skin edema. In addition, the detection of specific antibodies is of great importance - anticentromere, antitopoisomerase, anti-RNA polymerase. The last two groups of antibodies are most often detected in the diffuse cutaneous form of systemic scleroderma and are associated with an unfavorable prognosis.

Another important diagnostic method in this case is kidney biopsy. It will differentiate true scleroderma kidney from other diseases that occur with acute renal failure - acute interstitial nephritis, hemolytic uremic syndrome. Chronic scleroderma nephropathy should be differentiated from drug-induced kidney disease, the development of which is possible during the treatment of systemic scleroderma with penicillamine. Penicillamine therapy can lead to the development of nephrotic syndrome, in some cases with signs of renal dysfunction. Morphologically, this reveals a picture of membranous nephropathy. Discontinuation of the drug with a subsequent increase in the dose of prednisolone leads to the elimination of nephrotic syndrome, the disappearance of proteinuria and the normalization of renal function.

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