|Year : 2012 | Volume
| Issue : 3 | Page : 279-282
J Gupta1, Jonathan M Daniel1, V Vasudevan2
1 Department of Oral Medicine and Radiology, Mahatma Gandhi Postgraduate Institute of Dental Sciences, Gorimedu, Indira Nagar, Pondicherry, India
2 Department of Oral Medicine and Radiology, Krishnadevaraya Dental College and Hospital, Bengaluru, India
|Date of Web Publication||21-Dec-2012|
Department of Oral Medicine and Radiology, Mahatma Gandhi Postgraduate Institute of Dental Sciences, Gorimedu, Indra Nagar, Pondicherry - 605 006
Source of Support: None, Conflict of Interest: None
| Abstract|| |
Rabson-Mendenhall syndrome is a rare, autosomal recessive disorder affecting insulin receptor. This disorder is characterized by insulin-resistant diabetes mellitus, hyperinsulinemia, deficiency of subcutaneous fat, acanthosis nigrican, growth retardation, coarse and senile appearance, precocious puberty, and dental prematurity, enlarged genitalia, and pineal hyperplasia. Mutations of the insulin receptor gene affecting insulin action appear to be the basic mechanism underlying this syndrome. Herein, we present a case report on Rabson-Mendenhall syndrome in a 9-year-old girl.
Keywords: Acanthosis nigrican, diabetes, insulin resistance, precocious puberty
|How to cite this article:|
Gupta J, Daniel JM, Vasudevan V. Rabson-Mendenhall syndrome. J Indian Soc Pedod Prev Dent 2012;30:279-82
| Introduction|| |
Rabson-Mendenhall syndrome is a rare insulin receptor disorder characterized by severe insulin resistance  , developmental abnormalities, and acanthosis nigricans. It is a type A insulin-resistant disease wherein mutation of the insulin receptor gene appears to be the basic mechanism underlying this syndrome. The available literature regarding this syndrome is scanty. So this clinical report will be of assistance in diagnosing this particular syndrome. This clinical report becomes highly important to pediatric dentists as they may be the first to diagnose this rare genetic disorder.
Herein, we present a 9-year-old girl with clinical feature of Rabson-Mendenhall syndrome.
| Case Report|| |
A 9-year-old girl reported to the Department of Oral Medicine and Radiology, Mahatma Gandhi Postgraduate Institute of Dental Sciences, Pondicherry, India with a chief complaint of inability to close the mouth and crowded teeth. Patient's parents reported a history of first degree consanguineous marriage. Medical history of patient revealed precocious puberty.
On examination patient was lean and appeared malnourished with lack of subcutaneous fat [Figure 1]. She presented with very unusual clinical features like velvety hyperpigmentation of the skin particularly of skin fold region over the nape [Figure 2] and in the axilla suggestive of acanthosis nigricans.
She had generalized hirsutism with thick eyebrows, dense hair on the scalp, low hair line, short forehead, flattened cheek, and depressed nasal bridge [Figure 3]. Maxillary hypoplasia with anterior open bite was present. Lips had dry and scaly appearance [Figure 3]. Nails of both hands and feet were thick and appeared brittle [Figure 4] and [Figure 5]. Intra-oral examination revealed poor oral hygiene with chronic marginal gingivitis. Narrow maxillary arch with palatally positioned right lateral incisor [Figure 6] and crowded teeth were noted. Premature eruption of permanent dentition with macrodontia of central incisor was noted. Macroglossia with enlarged filliform papilla and vertical furrows were present on lateral surface of tongue. On the basis of clinical features a provisional diagnosis of Rabson-Mendenhall syndrome was given. Differential diagnosis of Leprechaunism, Berardinelli-Seip syndrome, Alstrom's syndrome, and Down syndrome were considered. Radiographic examination [Figure 7] of the patient revealed premature eruption of permanent teeth. Two-third root formation of second molars in all the four quadrants with crown formation of third molars was suggestive of dental prematurity for an individual with chronological age of 9 years. Medical records revealed abnormal post-glucose challenge that was 250-275 mg/dl (normal 110-140 mg/dl). However, fasting blood sugar level was under control as she was under treatment for insulin-resistant diabetes mellitus (metformin, 250 mg/twice daily). Hyperinsulinemia with blood insulin level of 50-56 mU/L (normal range 1.7-31 mU/L) was present. On the basis of clinical findings, medical records, and radiographic findings, a clinical diagnosis of Rabson-Mendenhall syndrome was made.
|Figure 3: Characteristic senile coarse facial appearance, broad eyebrows large tongue and thick scaly lips|
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|Figure 6: Narrow maxillary arch with palatally placed lateral incisor and crowded teeth|
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|Figure 7: Orthopantamogram shows erupted second molars and developing third molar (dental prematurity)|
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| Discussion|| |
In 1950, Mendenhall described a child with severe insulin-resistant diabetes  in whom, there was presence of hyperplasia of pineal gland at post-mortem. In 1956, Rabson and Mendenhall reported three siblings with extreme insulin-resistant diabetes, acanthosis nigricans, thick rapidly growing scalp hairs, phallic enlargement, precocious pseudo-puberty, markedly thickened nails, dental abnormality, and pineal hyperplasia.  Later in 1975, West et al., described siblings with similar clinical features. 
Mutation in insulin receptor gene causes the severe insulin-resistant syndrome like Leprechaunism and Rabson-Mendenhall syndrome. Their metabolic feature includes fasting blood hypoglycemia, post-prandial hyperglycemia, and extremely elevated insulin levels. Due to extreme insulin resistance patient fails to respond to endogenous and exogenous insulin with intra-uterine and post-natal growth retardation leading to dysmorphic features, lack of subcutaneous fat, acanthosis nigricans, and enlargement of genitalia, hirsutism, paradoxical fasting hypoglycemia, and post-prandial hyperglycemia.
In addition to insulin resistance and acanthosis nigricans, Rabson-Mendenhall syndrome is characterized by short stature, abnormalities in nail and teeth, and pineal hyperplasia. The clearest distinction between Rabson-Mendenhall syndrome and Leperchaunism is based on age of survival of the patient. Patient with Leperchaunism usually die within first 2 years of life. Rabson-Mendenhall though less severe than Leperchaunism has poor prognosis. 
Clinical features of our case (acnthosis nigrican, hypertrichosis, and thick nails, dental prematurity and precocious puberty with hyperinsulinemia) are well correlated with the original description of the syndrome. ,
Coarse facial appearance, macroglossia, thickened lips, depressed nasal bridge, and dry skin are well correlated with the findings reported by Alaei et al.  The dental findings are also well correlated with findings reported by Renuka et al.  It can be differentiated from Leprechaunism from the age of the patient as a patient suffering from this condition rarely survives beyond 2 years.
Clinical features of lipodystrophic syndrome (Berardinelli-Seip syndrome) are shared with Rabson-Mendenhall syndrome. But apart from abnormalities of adipose tissue, patient suffering from lipodystrophic syndrome shows hyperlipidemia and hepatic disease as a major and life-threatening feature.
Alstrom's syndrome is a syndrome that is also associated with severe insulin resistance and acanthosis nigricans but can be differentiated from Rabson-Mendenhall syndrome by characteristic retinal pigment degeneration and sensorineural deafness. 
Few clinical features of Rabson-Mendenhall syndrome are similar to Down's syndrome (flat nasal bridge, a flat profile, and a large grooved tongue protruding from the mouth). However, it is a chromosomal disorder and not related to hyperinsulinemia.
Treatment of this condition is very difficult and no definitive treatment for this condition is documented in the literature apart from addressing the hyperinsulinemia and insulin resistance. Drug therapy is not satisfactory for the insulin-resistant patient. Use of human IGF-I alone or in combination with its binding protein has shown some promising results.  Early mortality of patient suffering from this condition is due to the complication of insulin-resistant diabetes.
| Conclusion|| |
In conclusion, though it is a rare genetic disorder the clinical features are very characteristic and well identified which favors the clinical diagnosis of this syndrome. This syndrome has many overlapping clinical features with Leperchaunism, however, it is less severe with more life expectancy. Therapy with IGF-I remains the first choice of treatment for insulin resistance syndromes. Novel therapies targeted at correcting the defect in a specific manner are needed. A clear understanding of insulin signaling may lead to the future development of drug and gene therapies that will help in treating insulin resistance syndromes and associated debilitating disorders.
| References|| |
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[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6], [Figure 7]
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