Spastic Paraplegia 20, Autosomal Recessive

Alternative Names

  • SPG20
  • Troyer Syndrome
  • Spastic Paraparesis, Childhood-Onset, with Distal Muscle Wasting
  • Spastic Paraplegia, Autosomal Recessive, Troyer Type

Associated Genes

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WHO-ICD-10 version:2010

Diseases of the nervous system

Systemic atrophies primarily affecting the central nervous system

OMIM Number


Mode of Inheritance

Autosomal recessive

Gene Map Locus



Spastic Paraplegia 20, autosomal recessive (Troyer syndrome) belongs to a group of rare genetic disorders known as hereditary spastic paraplegias. These disorders are characterized by progressive muscle stiffness and the development of paralysis of the lower limbs. There are two types of hereditary spastic paraplegias: the pure types that involve the lower limbs and the complex types that involve the lower limbs and can also affect the upper limbs to a lesser degree, the structure or functioning of the brain, and the nerves connecting the brain and spinal cord to muscles and sensory cells that detect sensations such as touch, pain, heat, and sound (i.e., the peripheral nervous system).

Troyer syndrome is a complex hereditary spastic paraplegia, characterized mainly by progressive stiffness, weakness and wasting of the lower leg muscles. The thumb muscle and speech is also affected. It causes the degeneration and death of muscle cells and motor neurons throughout the lifetime of the patient, leading to a slow progressive decline in muscle and nerve function.

SPG20 is a rare disorder, with only 20 cases having been reported in the Old Order Amish population. Diagnosis is based on clinical evaluation and the family history of the person. DNA analysis can help in diagnosing particular forms of HSP. There are no specific treatments. Both symptomatic treatment used for spasticity, such as muscle relaxants, and supportive medical management could be helpful.

Molecular Genetics

Troyer Syndrome has an autosomal recessive pattern of inheritance. A mutation in the SPG20 gene was identified in an extended Amish family. This gene encodes a protein called Spartin, which is found in many body tissues, including the nervous system.

Epidemiology in the Arab World

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Subject IDCountrySexFamily HistoryParental ConsanguinityHPO TermsVariantZygosityMode of InheritanceReferenceRemarks
275900.1.1United Arab EmiratesMaleYesYes Progressive cerebellar ataxia; Global de...NM_015087.4:c.1324G>CHomozygousAutosomal, RecessiveBizzari et al. 2017 Proband
275900.1.2United Arab EmiratesFemaleYesYes Limb dystonia; Spastic ataxia; Global de...NM_015087.4:c.1324G>CHomozygousAutosomal, RecessiveBizzari et al. 2017 Sister of 275900.1.1
275900.1.3United Arab EmiratesMaleYesYes Global developmental delay; Brisk reflex...NM_015087.4:c.1324G>CHomozygousAutosomal, RecessiveBizzari et al. 2017 Brother of 275900.1....
275900.1.4United Arab EmiratesFemaleYesYes Developmental regression; Short stature;...NM_015087.4:c.1324G>CHomozygousAutosomal, RecessiveBizzari et al. 2017 First cousin of 2759...
275900.1.5United Arab EmiratesFemaleYesYes Developmental regressionNM_015087.4:c.1324G>CHomozygousAutosomal, RecessiveBizzari et al. 2017 First cousin of 2759...

Other Reports


Manzini et al. (2010) reported two related Omani families with Troyer syndrome. The first family had nine children, four of whom (3 males, 1 female) were affected. The second family had eight children, two of whom were affected. All the patients presented with short stature and dysarthria, and were delayed in reaching motor and cognitive developmental milestones. They all had some difficulties in walking, with clumsy, mildly spastic gait. The most common physical features among the patients were relative hypertelorism and overgrowth of the maxilla leading to overbite, hand and feet anomalies such as brachydactyly (5/6 patients), hammer toes, and pes cavus. Nonspecific skeletal malformations were observed in the hands such as clinodactyly, camptodactyly, and hypoplastic 5th middle phalanges. The clinical descriptions of the affected individuals were matched to Amish Troyer syndrome.

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