Background: Nonimmune neonatal goitrous hypothyroidism is a rare cause of neck mass and stridor. Retropharyngeal extension, described in 7% of cases of goitre spreading outside the thyroid bed, represents a diagnostic dilemma that requires a systematic multimodality imaging approach combined with hormonal and genetic analysis. We report the case of a one-week-old baby who presented with stridor and respiratory distress, without palpable neonatal goitre and whose biochemical profile suggested defective thyroglobulin synthesis.
Case: A eight-day- old term male infant was admitted to the Neonatal Intensive Care Unit for assessment and management of persistent stridor. Clinical examination of his neck was normal. Microlaryngoscopy and bronchoscopy (MLB) revealed subglottic stenosis and neck MRI scan confirmed a large goitre with retropharyngeal extension. Following a borderline TSH result of 17 mU/l (normal range, NR <8 mU/l) on neonatal screening , venous hormonal profile showed modest TSH elevation (28.7 mU/l, NR: 0.35 - 5.50 mU/l) with low free T4 (6 pmol/l, NR 10.4 - 22.7 pmol/l), normal -high free T3 (9.2 pmol/l, NR 4.6 - 10.1 pmol/l) and undetectable serum thyroglobulin concentrations (<0.2 ug/l, NR 7.82-79.5 ug/l). Maternal thyroid function was normal and thyroid stimulating immunoglobulins were not detected in mother or neonate. Treatment with levothyroxine 11.5 mcg/kg/day was started to normalise serum TSH concentrations, thereby mitigating thyroidal trophic stimulation and goiter growth, however, due to persistent respiratory distress, intubation and ventilation were required. Isthmectomy was performed at 22 -days- old to facilitate extubation, since two weeks of medical treatment had not ameliorated goitre size. Histopathology and immunohistochemistry findings were consistent with defective thyroglobulin synthesis, although thyroglobulin sequencing results are still awaited. Levothyroxine dose was optimised, repeat MLB showed significant improvement of subglottic stenosis and follow up MRI scan showed reduction of the goitre size without any focal thyroid lesions. The baby was extubated on day 43 of life and discharged home on thyroxine 5.7 mcg/kg/day when he was two months old. Multi-disciplinary management was key in his progress and successful discharge.
Conclusions: Dyshormonogenetic retropharyngeal goiter is a rare case of persistent stridor in the neonatal period. TSH elevation, combined with raised FT3:FT4 ratio and disproportionately low serum thyroglobulin levels in the context of goitre and TSH elevation, should trigger molecular evaluation for thyroglobulin mutations. Suppressive therapy with thyroxine is not always effective in reducing the size of goitre associated with this condition and surgical intervention may be required.
22 Sep 2021 - 26 Sep 2021