Most patients with systemic lupus erythematosus (SLE) have elevated titers of antinuclear antibodies (ANA). However, around 10% of patients with SLE have normal titers of ANA, which can result in a delay or mistake in diagnosis.
Clinical features may include:
(1) vasculitic skin lesions
(2) alopecia
(3) oral ulcerations
(4) photosensitivity
(5) Raynaud's phenomenon
(6) serositis
(7) lupus-like nephropathy
(8) arthralgies
(9) cranial nerve palsy
(10) neuropsychiatric symptoms (especially if antr-ribosomal P protein positive)
(11) in a female, neonatal lupus syndrome in offspring
Laboratory features:
(1) The patient may show a variable presence of antibodies to Ro/SSA, anti-ribosomal P protein, or other autoantibodies.
(2) Sometimes an antinuclear antibody is present but not detected if reacting against mouse liver cells. It may be detectable if reacted with another substrate.
(3) Some cases may be due to a technical error in performing the ANA test.
ANA-negative SLE starting in childhood may be related to a homozygous deficiency of a component in the classical complement pathway (C1q, C1r, C1s, C4, C2).
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