Identifying Marine-Lenhart syndrome on a (99m)Tc-pertechnetate thyroid scan.

Sir,

Graves disease coexistent with a nodular goiter is referred to as Marine-Lenhart syndrome. It is also called nodular Graves disease.[1] We present here the technetium pertechnetate thyroid scan image with an emphasis for endocrinologists and nuclear medicine physicians to identify this variant, as it is more resistant to radioiodine than the classical diffuse toxic goiter of Graves disease.

A 38-year-old male presented to our institution with complaints of weight loss and tremors since 2 months. His thyroid profile was suggestive of thyrotoxicosis. A thyroid scan done 20 minutes after intravenous administration of 5 mCi 99mTc-Pertechnetate showed an enlarged thyroid with intense uptake in both lobes as well as a left thyroid nodule with intense uptake [Figure 1]. Background tracer activity was suppressed. His Radioactive Iodine Uptake (RAIU) was 31.8% at 2 h (laboratory normal (5-15%)) and 83.6% at 24 h (laboratory normal (15-35%)).

Figure 1

99mTc-pertechnetate thyroid scan showing an enlarged thyroid with intense uptake in both lobes as well as a left thyroid nodule (arrow) with intense uptake [Figure 1]. Background tracer activity appears suppressed

The association of thyroid nodules with Graves disease is found in 25-30%[23] of patients affected by Graves disease. More than 95% of these nodules are hypoactive and a small percentage is hyperactive. Therefore, patients with Marine–Lenhart syndrome can have thyrotoxicosis due to the Graves disease as well as the nodule, which may be hyperfunctioning at the outset or may develop autonomicity after a variable period of time.[456] Genetic alterations of the thyroid stimulating hormone TSH receptors are suspected in the development of the Marine–Lenhart syndrome in patients affected by the Graves disease.

The amount of radioiodine required to relieve the hyperthyroidism in these patients is greater than the corresponding mean, median, or mode dose required for patients with diffuse toxic goiter. This is said to be the result of the large size of these goiters as well as the relative radio-resistance of some of them.[1] This variant of Graves disease should therefore be kept in mind.