Uniparental Disomy of Chromosome 1 Causing Concurrent Charcot-Marie-Tooth and Gaucher Disease Type 3

Uniparental disomy (UPD) can be the cause of atypical disease manifestations in patients with Mendelian disorders. Consideration of this disease mechanism proved essential in our evaluation of a 3-year-old boy, referred to the NIH Clinical Center for further evaluation of Gaucher disease (GD). ### Case report. The patient was born at term to non-consanguineous parents with a paternal family history of autosomal dominant Charcot-Marie-Tooth disease type I (CMT1). His medical history included moderate sensorineural hearing loss, Wolff-Parkinson-White arrhythmia, bicuspid aortic valve, and motor delay, ambulating at 26 months. At 17 months, hepatosplenomegaly was noted and a bone marrow biopsy led to the diagnosis of type 3 GD. Molecular analysis revealed homozygosity for the NM_000157.2:c.1448T>C (L444P) mutation in the glucocerebrosidase gene ( GBA ). He began enzyme replacement therapy (Imiglucerase, 120 U/kg biweekly), with significant resolution of his organomegaly. On examination, he had mild hepatosplenomegaly, bilateral pes cavus, externally rotated hips, genu valgus, hammertoes, decreased muscle tone, and mild foot drop. Reflexes were depressed in the upper extremities and absent in knees and ankles. Ophthalmologic evaluation revealed nystagmus, dysconjugate gaze, slowed, hypometric horizontal saccades, and decreased pupillary constriction (Adie-like). Nerve conduction studies were 13 …