We present a unique case of familial primary Sjogren's syndrome (pSS) involving a father and son that challenge several key features of this disease onset.
A 20‐year‐old man (fig 11)) was referred with a 4‐year history of recurrent parotitis and persistent bilateral parotid swelling. He also had increasing fatigue and night sweats for 3 months and cosmetically unacceptable parotid swellings. Although Schirmer's test was normal, he was found to have positive Ro, La and antinuclear antibodies. Computerised tomography scans of his abdomen and chest showed no abnormality. Subsequent parotid biopsy showed a low‐grade mucosa‐associated lymphatic tissue (MALT) lymphoma. A diagnosis of pSS that was complicated by MALT lymphoma was made. The parotid swellings were reduced by 50% with no further fatigue or night sweats after the introduction of prednisolone 30 mg once daily and hydroxychloroquine.
On subsequent inquiry, his 55‐year‐old father was found to have had a 15‐year history of bilateral parotid swellings for which he never sought medical attention (fig 22).). He was a mechanical engineer who gave a 15‐year history of dry eyes and mouth and recurrent cervical lymphadenopathy. His Schirmer's test was strongly positive, with measurements of 2 mm in his left eye and 0 mm in his right. He also had positive Ro and La antibodies along with hypergammaglobulinaemia (immunoglobulin (Ig)G 25.2 (4.9–16.1) g/l, IgM 3.95 (0.60–2.1) g/l), lymphopenia (lymphocyte 0.4×109 (1.1–3.5)/l) and an erythrocyte sedimentation rate of 92 (1–10) mm/h. As he remained relatively asymptomatic apart from his ocular and oropharyngeal dryness, he was treated with artificial tears only.
This case report highlights several unusual features. Although familial clustering of different autoimmune diseases in individuals with pSS have been reported, familial cases of pSS at any age are uncommon.1 A literature search shows no previous documented cases of familial pSS involving father and son. pSS has a peak incidence in the fourth and fifth decades of life, with a female:male ratio of 9:1.2 Both of our patients were male members and one patient presented with symptoms since his teenage years.
Although a genetic predisposition to pSS appears to exist, the level of genetic contribution is unknown.1 Family members with pSS seem to share similar phenotypes, with almost identical clinical presentation and serological data.3,4 In our case, the proband presented in the patient's early 20s with MALT lymphoma, whereas his father had lived with the symptoms of pSS undiagnosed (table 11).). Lymphoma is usually a late complication of pSS, with a median time from pSS diagnosis to lymphoma diagnosis of 7.5 years.5,6
 | Table 1  Classification criteria as defined by the European Study Group on classification of Sjogren's Syndrome8 in index case and parent |
Genetic studies of pSS already show strong associations with major histocompatibility complex genes, including HLA‐DR3, which may also determine the severity of the autoimmune disease.7 Future studies comparing the clinical, serological and genetic features of familial pSS are needed to gain further understanding of this complex multifactorial disorder.