Scalp defects-postaxial polydactyly syndrome

Scalp defects-postaxial polydactyly syndrome is a very rare genetic disorder characterised by congenital defects of the scalp and type A postaxial polydactyly, with severe intellectual disability as an additional finding头皮缺陷-轴后多指（趾）畸形综合征是一种极其罕见的遗传病，以头皮先天性缺陷和 A 型轴后多指（趾）畸形为特征，严重智力障碍是额外发现。

The condition is thought to be inherited in an autosomal dominant manner, and approximately nine cases from two families have been described in medical literature该病被认为以常染色体显性模式遗传，医学文献中描述了来自两个家庭的约9个病例。

The syndrome is classified as an ultra-rare disorder with skeletal, cutaneous and neurological involvement该综合征归类为具有骨骼、皮肤和神经学受累的超罕见病。

Terminology and classification

• Scalp defects-postaxial polydactyly syndrome is classified as a rare genetic disorder with cutaneous, skeletal and neurological features头皮缺陷-轴后多指综合征归类为具有皮肤、骨骼和神经学特征的罕见遗传病。^[1]
• MONDO catalogues the condition as MONDO:0008403, Orphanet assigns ORPHA:1003, and OMIM 181250 records the causative locusMONDO 将该病编目为 MONDO:0008403，Orphanet 赋予 ORPHA:1003，OMIM 181250 记录致病位点。^[2]
• Cross-references include MeSH C536622 and UMLS C1867021, and the condition is classified as an ultra-rare disease交叉引用包括 MeSH C536622 和 UMLS C1867021，该病归类为超罕见病。^[2]
• The condition is distinguished from other polydactyly syndromes by the combination of scalp defects and postaxial polydactyly该病通过头皮缺陷和轴后多指的组合与其他多指综合征区分。^[1]
• The syndrome is distingued from trisomy 13 syndrome, which also features scalp defects and polydactyly but has a different genetic basis该综合征不同于13三体综合征，后者也以头皮缺陷和多指为特征，但遗传基础不同。^[2]
• The syndrome meets the Chinese rare disease criterion of fewer than 140,000 patients nationwide该综合征符合中国罕见病标准（全国患者数少于14万）。^[1]

History

• Scalp defects-postaxial polydactyly syndrome was described in medical literature in reports of affected individuals from two families头皮缺陷-轴后多指综合征在医学文献中描述于两个家庭的受累个体报告中。^[1]
• The condition was recognised as a distinct entity based on its characteristic combination of scalp defects and postaxial polydactyly该病基于头皮缺陷和轴后多指的特征性组合被认定为独立实体。^[1]
• The autosomal dominant inheritance pattern was inferred from the occurrence in multiple generations of affected families常染色体显性遗传模式从受累家庭多代中的发生推断。^[1]
• The condition was subsequently included in rare disease databases and classified by MONDO and Orphanet该病随后被纳入罕见病数据库，并由 MONDO 和 Orphanet 分类。^[2]
• The genetic cause of the syndrome has not been definitively identified, and the condition remains a clinical diagnosis该综合征的遗传原因尚未确定，该病仍是临床诊断。^[1]

Epidemiology

• Scalp defects-postaxial polydactyly syndrome is extremely rare, with approximately nine cases from two families described in medical literature头皮缺陷-轴后多指综合征极其罕见，医学文献中描述了来自两个家庭的约9个病例。^[1]
• The condition is thought to be inherited in an autosomal dominant pattern, based on its occurrence in multiple family members根据其在多个家庭成员中的发生，该病被认为以常染色体显性模式遗传。^[1]
• Symptoms are present from birth, with scalp defects and polydactyly being apparent at delivery症状从出生时即存在，头皮缺陷和多指在分娩时即明显。^[1]
• Both sexes may be affected, and no specific geographic or ethnic predilection has been reported两性均可受累，未报告特定的地理或民族偏好。^[1]
• The condition is associated with severe intellectual disability, which contributes to significant morbidity该病与严重智力障碍相关，这导致显著的发病率。^[1]

Pathophysiology

• The genetic cause of the syndrome has not been identified, and the condition is presumed to result from a defect in early embryonic development该综合征的遗传原因尚未确定，该病被推定源于早期胚胎发育缺陷。^[1]
• The scalp defects result from failure of the skin to close properly over the skull during development, a condition known as aplasia cutis congenita头皮缺陷源于发育期间皮肤未能在颅骨上正确闭合，这种情况称为先天性皮肤发育不全。^[1]
• The postaxial polydactyly results from abnormal limb bud development during embryogenesis, leading to extra digits on the postaxial side轴后多指源于胚胎发生期间肢芽发育异常，导致轴后侧的额外指（趾）。^[1]
• The intellectual disability is thought to result from abnormal brain development associated with the underlying genetic defect智力障碍被认为源于与潜在遗传缺陷相关的脑发育异常。^[1]
• The combination of cutaneous, skeletal and neurological features suggests a defect in a gene involved in early development皮肤、骨骼和神经学特征的组合提示涉及早期发育的基因缺陷。^[1]
• The involvement of multiple organ systems is consistent with a developmental field defect affecting the embryo early in gestation多器官系统的受累与影响妊娠早期胚胎的发育区域缺陷一致。^[1]

Clinical features

• The cardinal features are congenital defects of the scalp and type A postaxial polydactyly主要特征是头皮先天性缺陷和 A 型轴后多指。^[1]
• The scalp defects present as areas of aplasia cutis congenita, with absent skin and underlying tissue over the vertex of the skull头皮缺陷表现为先天性皮肤发育不全区域，颅顶皮肤和下层组织缺失。^[1]
• The postaxial polydactyly presents with extra digits on the ulnar or fibular side of the hands and feet轴后多指表现为手和足的尺侧或腓侧额外指（趾）。^[1]
• Severe intellectual disability is an additional finding, and affected individuals may have developmental delay严重智力障碍是额外发现，受累个体可能有发育迟缓。^[1]
• Other features may include facial dysmorphism and other skeletal abnormalities其他特征可能包括面部畸形和其他骨骼异常。^[1]
• Complications include infection of the scalp defects, which may require surgical management, and the functional impact of intellectual disability并发症包括头皮缺陷的感染，可能需要手术管理，以及智力障碍的功能影响。^[1]

Diagnosis

• Diagnosis is based on the characteristic clinical combination of scalp defects, postaxial polydactyly and intellectual disability诊断基于头皮缺陷、轴后多指和智力障碍的特征性临床组合。^[1]
• Clinical examination identifies the scalp defects and polydactyly, while developmental assessment evaluates the intellectual disability临床检查识别头皮缺陷和多指，而发育评估评估智力障碍。^[1]
• Skeletal radiography may be used to assess the polydactyly and other skeletal abnormalities骨骼 X 线可用于评估多指和其他骨骼异常。^[1]
• The differential diagnosis includes trisomy 13 syndrome, which features scalp defects, polydactyly and other midline defects鉴别诊断包括13三体综合征，以头皮缺陷、多指和其他中线缺陷为特征。^[2]
• Chromosomal microarray may be performed to exclude chromosomal abnormalities such as trisomy 13可进行染色体微阵列以排除染色体异常如13三体。^[1]
• Genetic counselling is recommended for affected families given the likely autosomal dominant inheritance鉴于可能的常染色体显性遗传，建议对受累家庭进行遗传咨询。^[1]

Management

• Management is supportive and multidisciplinary, targeting the individual manifestations of the syndrome管理是支持性和多学科的，针对该综合征的个体表现。^[1]
• Management of scalp defects may include surgical repair or conservative wound care, depending on the size and severity头皮缺陷的管理可能包括手术修复或保守性伤口护理，取决于大小和严重程度。^[1]
• Polydactyly may be managed surgically to improve function and appearance多指可通过手术管理以改善功能和外观。^[1]
• Developmental support and educational interventions are important for managing intellectual disability发育支持和教育干预对于管理智力障碍很重要。^[1]
• Multidisciplinary care involving dermatology, orthopaedics, neurology and paediatrics is essential涉及皮肤科、骨科、神经科和儿科的多学科护理至关重要。^[1]
• The prognosis depends on the severity of the scalp defects and intellectual disability, with most patients requiring lifelong support预后取决于头皮缺陷和智力障碍的严重程度，大多数患者需要终身支持。^[1]

Research and controversies

• The genetic cause of scalp defects-postaxial polydactyly syndrome has not been identified, and the condition remains a clinical diagnosis头皮缺陷-轴后多指综合征的遗传原因尚未确定，该病仍是临床诊断。^[1]
• Whether the syndrome is a distinct entity or a variant of another developmental disorder is an area of discussion该综合征是独立实体还是另一发育疾病的变异型是讨论领域。^[1]
• Given the rarity of the condition, the clinical spectrum and natural history are not well characterized鉴于该病的罕见性，临床谱系和自然史尚未充分描述。^[1]
• The identification of the causative gene would improve diagnosis and distinguish the condition from trisomy 13 syndrome致病基因的鉴定将改善诊断并将该病与13三体综合征区分。^[1]
• Further research is needed to understand the pathophysiology and develop targeted therapies需要进一步研究以理解病理生理学并开发靶向治疗。^[1]

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