We present the case of a 26-year-old woman, with no previous history of interest, who, although previously well, began with mild odynophagia, an afternoon fever of up to 38.5º which resolved well with paracetamol, and general malaise. No accompanying chills or sweating crises. 4-5 days later, she noticed the appearance of lymph nodes in both laterocervical areas and started treatment with amoxicillin, 500 mg/8 h, on her own without observing any improvement.
Physical examination revealed the presence of lymph nodes in both laterocervical chains, of medium consistency, rolling, non-adherent, 1-2 cm in diameter and painless. There were no palpable lymphadenopathies at other levels or organomegaly. No goitre or pain on pressure over the thyroid region.
The analytical study showed leukocytosis with lymphocyte predominance, with an ESR of 22 mm/h. Liver function was preserved, there was no hypergammaglobulinaemia and mantoux was negative. Chest X-ray was normal. Serology for the viruses studied was negative (anti-EBV, CMV, HIV, HTLV-1, HV-6, toxoplasma and syphilis). In the immunological study: ANA: 1/40 (80), antiDNA: 13.4 IU/ml (50), antiRNA: negative, ENA-RNP: 0.45 and anticardiolipin: negative. Thyroid function was assessed: T3: 1.31 mg/L (0.6-1.6), T4: 84 mg/L (46-93), TSH: 6.3 mU/L (<7), TGB (antithyroglobulin): 20.17 U/mL (<60), TPO (antiperoxidase): 1071 U/mL. Thyroid scan was normal.
The fever disappeared after 12 days, but the lymph nodes remained unchanged, so a biopsy of two lymph nodes in the middle area of the right latero-cervical chain was performed, which was diagnostic. Histological examination was compatible with non-lymphocytic histiocytic necrotising lymphadenitis or Kikuchi-Fujimoto disease.
In the evolutionary control of thyroid function 5 months after the onset of the disease, a decrease in the titre of antithyroid antibodies was observed (TGB: 7.6 U/mL; TPO: 870 U/mL), maintaining normal thyroid hormone and TSH levels (2.95 mU/L). Our diagnosis was subacute lymphocytic thyroiditis associated with Kikuchi's disease.