Rapid Weight Gain in an Excessively Sleepy Girl With Asthma

Timothy D. Murphy, MD

Disclosures

October 09, 2020

This case illustrates some of the challenges facing clinicians who care for a "sleepy child." In the evolution of this child's care, multiple diagnoses were made and treated. The failure of her symptoms to respond to treatment resulted in further evaluation (and reevaluation of the data), which finally led to the diagnosis (narcolepsy with cataplexy) and her ultimate improvement and stabilization.

Hypersomnolence may be primary or it may be secondary to a poor night's sleep. The most common conditions seen in a pediatric sleep clinic that might lead to daytime sleepiness include sleep apnea, behavioral insomnia of childhood, restless sleeping (or, when more extreme, pediatric RLS), and delayed sleep phase disorder (DSPD). The latter is much more common in teenagers, with a prevalence of up to 7% in this age group.[3] However, youths with daytime hypersomnolence due to DSPD do not typically fall asleep easily at bedtime, as this patient did. Moreover, DSPD is unusual in an 8-year-old.

An insufficient quantity of sleep can usually be diagnosed on the basis of the history alone, but actigraphy is occasionally used when the history does not exclude difficulty in falling asleep or a circadian rhythm sleep-wake disorder.[4] Actigraphy was not included in this patient's workup.

Pediatric RLS is primarily diagnosed on the basis of history, but the use of strict criteria (which include that the child "relates a description in his or her own words" of leg discomfort) may lead to missing the diagnosis in children who can benefit from treatment but are unable to verbalize their feelings. Suboptimal levels of serum ferritin are associated with restless sleep in children, as is improvement with iron therapy. The use of dopaminergic medications typically requires a higher standard for the diagnosis of RLS and a failure to respond to iron therapy.[5,6] Published data regarding autism and attention-deficit/hyperactivity disorder (ADHD) increasingly suggest complex links between iron metabolism and brain function, including during sleep.[7,8] This patient's movements in bed and her behavioral and learning struggles led to the investigation of her iron stores and ferritin levels and a trial of treatment for RLS.

Hypersomnolence is associated with OSA more commonly in adults than in children. "Hyperactivity" or symptoms of ADHD are more frequently observed in children with OSA, although some sleepiness is still noted.[9] Most sleep centers consider an obstructive AHI of fewer than 1 event per hour (some use a threshold of 1.5) to be normal.[10] More pragmatically, the absolute score is useful in choosing a diagnostic billing code, but clinical decision-making also factors in the age of the patient and the severity of observed symptoms, considered formally or as a gestalt.[11]

This patient had a positive AHI, which is diagnostic of OSA, and underwent adenotonsillectomy without significant improvement. She was also treated with iron and vitamin C, without significant changes in her daytime sleepiness or her apparent sleep quality. Furthermore, her clinical care was complicated by the MSLT result, which documented hypersomnolence but not narcolepsy.

The diagnosis of narcolepsy was based primarily on clinical factors. Despite the positive AHI, snoring, leg movements, and low ferritin level, her condition did not improve after the adenotonsillectomy and iron therapy. As her case progressed, she developed more classic symptoms of cataplexy, such as feeling as if she would fall with laughter and falling asleep rapidly in conjunction with strong emotions. These findings, along with the rapid weight gain, pointed toward the diagnosis.

Some confusion along the path toward a diagnosis is common in narcolepsy. Comorbidities, including PLMD, RLS, and OSA, may be found in association with narcolepsy and can delay the diagnosis,[12] as certainly happened in this patient.

Narcolepsy affects about 1 in 2000 people. Two types are recognized: type 1 narcolepsy (previously referred to as narcolepsy with cataplexy) and type 2 narcolepsy (narcolepsy without cataplexy). Type 1 narcolepsy is considered an adult diagnosis by many pediatricians, but it frequently develops during adolescence, and onset after age 40 years is uncommon. Children may first present with a resumption of prolonged naps rather than prolonged nighttime sleep; nocturnal sleep is often somewhat disturbed initially. Cataplexy, multiple short naps during the day, hypnagogic hallucinations, and sleep-onset REM periods may be absent in young children, and repeated NPSGs and MSLTs over months to years may be required to make the diagnosis.

Although a retrospective analysis of sleep histories often reveals hypersomnolence for years prior to the diagnosis, it can be easily missed in the first decade of life.[13] Type 1 narcolepsy is caused by the loss of orexin neuropeptides, which are mediators of central nervous system (CNS) control of energy metabolism and maintenance of sleep-wake states. Rapid weight gain and precocious puberty can occur in children with type 1 narcolepsy. This patient's rapid weight gain started to make more sense once the diagnosis was made.[14]

In type 1 narcolepsy, the lack of consistent REM sleep at night leads to the intrusion of REM sleep features into the waking state. The diagnostic features include the tetrad of daytime sleepiness, cataplexy, hypnagogic hallucinations, and sleep paralysis. Specific questioning is usually required to elicit the history; only cataplexy is specific for narcolepsy. Patients often present initially with hypersomnolence alone, and other diagnostic findings may emerge over time.

The etiology of narcolepsy is unclear. The lack of orexin may be related to autoimmune disease or infectious diseases. Most patients with type 1 narcolepsy have HLA DQB1 (0602 allele), the gene complex that encodes for proteins on the surface of T cells. Additionally, some infections (most notably H1N1 influenza, as well as some vaccines for it) are associated with clusters of type 1 narcolepsy and reduced orexin levels.[15,16,17] However, measurement of cerebrospinal fluid (CSF) levels of orexin is not required to make the diagnosis of narcolepsy.

The diagnosis of type 1 narcolepsy can be clinically made in a child with a clear history of cataplexy, EDS, and an otherwise normal neurologic examination. In the absence of cataplexy, an NPSG followed by an MSLT can be used to make the diagnosis of narcolepsy. "Secondary narcolepsy" in the setting of CNS diseases such as hypothalamic tumors or arteriovenous malformations, following cerebrovascular accidents, or in association with multiple sclerosis or Niemann-Pick disease type C has been reported, but alternative causes of narcolepsy are vanishingly rare in childhood. The primary challenge is to rule out other sleep disorders causing the EDS; as in this patient, that may be difficult.

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