Cerebral Dysgenesis–neuropathy–ichthyosis–keratoderma Syndrome
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Cerebral dysgenesis–neuropathy–ichthyosis–keratoderma syndrome is a neurocutaneous condition caused by mutation in the
SNAP29 Synaptosomal-associated protein 29 is a protein that in humans is encoded by the ''SNAP29'' gene. Function This gene, a member of the SNAP25 gene family, encodes a protein involved in multiple membrane trafficking steps. Two other members of t ...
gene.


Presentation

CEDNIK syndrome is a rare congenital condition that presents as severe developmental failure of the
nervous system In biology, the nervous system is the highly complex part of an animal that coordinates its actions and sensory information by transmitting signals to and from different parts of its body. The nervous system detects environmental changes th ...
and the
epidermis The epidermis is the outermost of the three layers that comprise the skin, the inner layers being the dermis and hypodermis. The epidermis layer provides a barrier to infection from environmental pathogens and regulates the amount of water rele ...
. Clinical manifestations include
microcephaly Microcephaly (from New Latin ''microcephalia'', from Ancient Greek μικρός ''mikrós'' "small" and κεφαλή ''kephalé'' "head") is a medical condition involving a smaller-than-normal head. Microcephaly may be present at birth or it ...
, cerebral dysgenesis,
facial dysmorphism A dysmorphic feature is an abnormal difference in body structure. It can be an isolated finding in an otherwise normal individual, or it can be related to a congenital disorder, genetic syndrome or birth defect. Dysmorphology is the study of dysm ...
,
palmoplantar keratoderma Palmoplantar keratodermas are a heterogeneous group of disorders characterized by abnormal thickening of the stratum corneum of the palms and soles. Autosomal recessive, dominant, X-linked, and acquired forms have all been described. Types C ...
, and
ichthyosis Ichthyosis is a family of genetic skin disorders characterized by dry, thickened, scaly skin. The more than 20 types of ichthyosis range in severity of symptoms, outward appearance, underlying genetic cause and mode of inheritance (e.g., dominan ...
. These children usually have a normal intrauterine life and normal birth. The first symptoms to appear are abnormal eye movements, poor head and trunk control and failure to thrive. The facial dysmorphism is characteristic with elongated faces, antimongolian eye slant, slight hypertelorism and flat broad nasal root. Palmoplantar keratoderma and ichthyosis appears between 5 and 11 months of age. Soon features of psychomotor retardation as seen as a delay in major developmental milestones, becomes evident. Severe
peripheral neuropathy Peripheral neuropathy, often shortened to neuropathy, is a general term describing disease affecting the peripheral nerves, meaning nerves beyond the brain and spinal cord. Damage to peripheral nerves may impair sensation, movement, gland, or or ...
is common in these children. Early
macular degeneration Macular degeneration, also known as age-related macular degeneration (AMD or ARMD), is a medical condition which may result in blurred or no vision in the center of the visual field. Early on there are often no symptoms. Over time, however, som ...
is yet another clinical feature. Death is common by 5–10 years and is usually as a result of infection or aspiration pneumonia.


Pathophysiology

This condition is associated with a
loss-of-function mutation In biology, a mutation is an alteration in the nucleic acid sequence of the genome of an organism, virus, or extrachromosomal DNA. Viral genomes contain either DNA or RNA. Mutations result from errors during DNA or viral replication, mitos ...
in SNAP29 gene, encoding a member of the SNARE family of proteins which is involved in intracellular
vesicle fusion Vesicle fusion is the merging of a vesicle with other vesicles or a part of a cell membrane. In the latter case, it is the end stage of secretion from secretory vesicles, where their contents are expelled from the cell through exocytosis. Vesicles c ...
. Decrease in SNAP29 expression was found to result in abnormal lamellar granule maturation and secretion. Lamellar granules are organelles found in the upper epidermal layers of skin and is responsible for secretion of lipids, proteases and their inhibitors to stratum corneum during the formation of epidermal barrier. Due to the abnormal vesicle trafficking as a consequence of decreased SNAP29 there is abnormal deposition of epidermal lipids and proteases. The abnormal gene of CEDNIK disease was mapped on chromosome 22 by Sprecher E et al.


Diagnosis

Tendon reflexes are usually absent.
Nerve conduction studies A nerve conduction study (NCS) is a medical diagnostic test commonly used to evaluate the function, especially the ability of electrical conduction, of the motor and sensory nerves of the human body. These tests may be performed by medical spec ...
usually show decreased amplitude indicating decrease in the number of active neurons. Muscle biopsies show atrophy. Ophthalmologic evaluation show
hypoplastic Hypoplasia (from Ancient Greek :wikt:ὑπό, ὑπo- ''hypo-'' 'under' + πλάσις ''plasis'' 'formation'; adjective form ''hypoplastic'') is underdevelopment or incomplete development of a tissue or organ.sensorineural hearing loss Sensorineural hearing loss (SNHL) is a type of hearing loss in which the root cause lies in the inner ear or sensory organ (cochlea and associated structures) or the vestibulocochlear nerve (cranial nerve VIII). SNHL accounts for about 90% of rep ...
is present. Magnetic resonance imaging of the brain shows abnormalities of the
corpus callosum The corpus callosum (Latin for "tough body"), also callosal commissure, is a wide, thick nerve tract, consisting of a flat bundle of commissural fibers, beneath the cerebral cortex in the brain. The corpus callosum is only found in placental mam ...
and
cortical dysplasia Focal cortical dysplasia (FCD) is a congenital abnormality of brain development where the neurons in an area of the brain failed to migrate in the proper formation in utero. ''Focal'' means that it is limited to a focal zone in any lobe. Focal co ...
, with
pachygyria Pachygyria (from the Greek "pachy" meaning "thick" or "fat" gyri) is a congenital malformation of the cerebral hemisphere. It results in unusually thick convolutions of the cerebral cortex. Typically, children have developmental delay and seizures, ...
and
polymicrogyria Polymicrogyria (PMG) is a condition that affects the development of the human brain by multiple small gyri ( microgyri) creating excessive folding of the brain leading to an abnormally thick cortex. This abnormality can affect either one region o ...
.


See also

* Arthrogryposis–renal dysfunction–cholestasis syndrome *
List of cutaneous conditions Many skin conditions affect the human integumentary system—the organ system covering the entire surface of the body and composed of skin, hair, nails, and related muscle and glands. The major function of this system is as a barrier against t ...
* Chediak Higashi syndrome *
Griscelli syndrome Griscelli syndrome is a rare autosomal recessive disorder characterized by albinism (hypopigmentation) with immunodeficiency, that usually causes death by early childhood. Researchers have developed three different classifications of the form of ...
* Hermansky-Pudlak syndrome * Sjogren Larsson syndrome


References


External links

Genodermatoses {{Dermatology-stub