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Letter to the Editor |
Service d’hémato-oncologie Pédiatrique (J.D.), Hopital Trousseau, 75012 Paris, France; and Service d’endocrinologie Pédiatrique (M.P.), Hopital Necker, 75015 Paris, France
Address correspondence to Michel Polak, M.D., Ph.D., Service d’endocrinologie Pédiatrique, Hopital Necker, 149 rue de Sèvres, 75015 Paris, France. E-mail: michel.polak{at}nck.ap-hop-paris.fr.
To the editor:
We agree that magnetic resonance imaging (MRI) studies of the anterior and posterior pituitary must be interpreted according to the timing of pituitary symptom onset in a range of diseases, including Langerhans cell histiocytosis (LCH). In our study (1), MRI was performed shortly (median, 7 wk) after diabetes insipidus (DI) onset in patients who were free of GH deficiency (GHD).
The main limitation of our study is the relatively small number of patients whose MRI studies could be reviewed (91 studies, 46 patients). This explains why we were very cautious when discussing the results, stating that "the value of MRI for early detection of patients at high risk of GHD must be confirmed."
Our study nonetheless has the merit of being the largest series of LCH-associated endocrinopathies reported to date and the largest series of MRI studies in this setting (2, 3, 4, 5, 6, 7). For example, Maghnie’s study (2) involved only 17 patients with LCH, of whom nine had pituitary involvement. This latter report did not state the interval between DI onset and MRI and did not analyze features potentially predictive of GHD (3). All clinical studies of LCH come up against both the rarity of the disease and the possibility of late permanent sequelae.
In their letter, Maghnie and Malattia (8) refer to a recent publication addressing the issue of central DI (CDI) in 71 children (9); CDI was related to LCH in only 12 patients, whereas it was idiopathic in 42 cases and tumor-related in 18 cases. Clearly, the progression patterns of these different entities are very different and should therefore be analyzed separately. No firm conclusions can be drawn on the basis of only 12 (or even 46) cases. In isolated CDI, the main reason why repeat MRI is recommended is to rule out a brain tumor. Until now, repeat MRI has not been recommended for patients with LCH, including those with pituitary dysfunction (10, 11), unless a new endocrinopathy or neurological symptoms occur.
However, our findings, and previous results from another group (12), show that repeat cranial MRI can provide very useful information in LCH and, incidentally, on pituitary status. We very recently reported that LCH patients with pituitary involvement have an increased risk of neurodegenerative changes (13). This rare but dramatic complication may be preceded by MRI changes, especially in the cerebellum. Because retinoids may slow this neurological degeneration, early diagnosis by means of repeated MRI may be beneficial (14).
If MRI becomes an accepted part of the standard management of patients with LCH endocrinopathy, the predictive value of anterior pituitary size for GHD could be addressed with more confidence.
Received May 11, 2004.
References
This article has been cited by other articles:
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  J. Donadieu and M. Polak Authors' Response: Timing of Pituitary Stalk Assessment in Langerhans Cell Histiocytosis: "When" Is Sometimes More Important than "What" J. Clin. Endocrinol. Metab., August 1, 2004; 89(8): 4166 - 4167. [Full Text] [PDF]
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