There exists a very small subgroup of patients with systemic sclerosis (SSc) who lack circulating antinuclear antibodies (ANA) and who do not have Raynaud's phenomenon (RP), research shows.
These patients also fail to meet any of the diagnostic criteria for known SSc mimics.
The researchers, led by Ulrich Walker (Basel University, Switzerland), say that prospective studies are needed to determine the "clinical presentation, evolution, and outcome of such patients."
They searched for SSc patients without ANA or RP using the EULAR Scleroderma Trials and Research (EUSTAR) database.
In total, 99.8% of patients included in the EUSTAR database had either detectable ANA or a history of RP, with just 12 patients having neither ANA nor RP.
In three of these ANA-negative and RP-negative patients, the SSc was not typical of any of the known mimics, such as nephrogenic systemic fibrosis (NSF), scleromyxoedema, eosinophilic fasciitis, pansclerotic morphea, and scleroedema adultorum.
One woman at age 57 years noticed a small pruritic morphea plaque on her abdomen and visited a dermatologist.
"Four months later she developed sclerodactyly, as well as tightness and non-pruritic induration of the forearms and the perioral skin, characteristic of SSc," write Walker and colleagues in Rheumatology.
In the second case, a 53-year-old female noted skin thickening on her trunk, as well as experiencing joint pain, contractures, episodic swelling of her hands, muscle weakness, and atrophy.
The patient later developed pulmonary fibrosis. According to the researchers, her presentation is compatible with ANA-negative and RP-negative SSc, "although a paraneoplastic syndrome must be considered."
And finally, a 25-year-old female noted thickening of the skin on her face and sclerodactyly and was diagnosed as having limited SSc.
In the remaining four patients, an unequivocal diagnosis of SSc could not be made.
"Our findings highlight the importance of conducting a thorough clinical evaluation when SSc is suspected in the absence of circulating ANA and RP," state the researchers.
Such an assessment should include a detailed medical history, including potential exposures to toxins such as gadolinium, organic solvents, and formaldehyde, among others.
The assessment should also include a thorough clinical examination to assess the anatomic distribution of skin sclerosis and the precise appearance of the skin.
Given that malignancies, including breast, pulmonary, and urogenital, among others, occur more frequently in patients with SSc than in the general population, the presence or the subsequent development of cancer in the ANA-negative and RP-negative SSc patients should be considered a "strong possibility," conclude Walker and colleagues.
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