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An inherited disorder characterized by hypotonia,
obesity, prominent incisors, and nonprogressive psychomotor retardation.
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Norio Syndrome; Pepper Syndrome;
Hypotonia-Obesity-Prominent Incisors Syndrome; Obesity-Hypotonia Syndrome.
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Approximately 100 cases have been described. An
increased frequency has been reported in Finland and in the Ashkenazi Jewish
population. Consanguinity is a known, but not constant risk factor. No sexual
predilection.
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Autosomal recessive. The mutation has been
mapped to 8q22-q23.
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The wide clinical variability of this disorder makes the
diagnosis difficult, which is primarily based on the clinical findings of
nonprogressive psychomotor retardation, microcephaly with characteristic
facial appearance, early hypotonia, joint hyperextensibility, clumsiness,
truncal obesity, mottled retina, and myopia in patients with isolated and
intermittent neutropenia (<2 × 109/mm3). Because of the
highly variable features, the diagnosis often is not made until late infancy
or even childhood.
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Pregnancy most often is uneventful and birth
occurs at term, however, poor fetal movement and growth and oligohydramnios
have been described in some patients. Poor feeding in the first year of life
is common. The disease involves the head and neck (microcephaly, thick scalp
hair, eyebrows and eyelashes, prominent nasal bridge and beak-shaped nose,
maxillary hypoplasia, prominent incisors [more the result of short and thin
upper lip, which becomes even more pronounced on smiling], micrognathia
[usually mild], short, upturned philtrum, high narrow palate, open mouth
appearance), the heart (mitral valve prolapse is common, but rarely of clinical
significance, progressive left ventricular dysfunction may occur with
increasing age), the eyes (wave-shaped, downward slanting palpebral
fissures, progressive pigmentary retinopathy, chorioretinal dystrophy, optic
atrophy, early myopia, strabismus, vision deteriorates with age and patients
are severely handicapped by the fourth to fifth decade of life), the central
nervous system (mental retardation, delayed motor milestones, seizures,
generalized hypotonia), and the skeleton (short stature secondary to growth
hormone deficiency, kyphoscoliosis often starting after puberty, joint
hyperextensibility [particularly hands, feet, knees], cubiti valgi, genua
valga, narrow hands and feet with slender fingers and toes, camptodactyly,
shortened metatarsals). Other features may include low birth weight,
transverse palmar creases, obesity (although less common than initially
thought), generally cheerful, socially interactive and cooperative
personality, delayed puberty, and mild-to-moderate neutropenia (78% of
patients), which does not appear to predispose the patients to infection.
Stridor occurs in about one fourth of patients and most often is a result of
laryngomalacia. Vocal cord paralysis was responsible for tracheostomy for
more than 1 year in one patient. Lifespan appears to be normal.
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A detailed cardiovascular evaluation
should be performed (clinically, electrocardiography, echocardiography).
Evaluate head and neck anatomy with regard to airway management because of
craniofacial anomalies and prominent teeth (radiographs may be required).
Evaluate neurologic status (clinically, computed tomography scans or
magnetic resonance imaging, electroencephalography). Obtain a complete blood
count with white cell differentiation (neutropenia).
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The combination of prominent incisors,
maxillary hypoplasia, and micrognathia suggests direct laryngoscopy and
tracheal intubation may be difficult. Spontaneous ventilation should be ...