Editing Microcephaly (section)

==Causes==
Microcephaly is a type of [[cephalic disorder]]. It has been classified in two types based on the onset:<ref>{{cite journal |last1=Ashwal |first1=S. |last2=Michelson |first2=D. |last3=Plawner |first3=L. |last4=Dobyns |first4=W. B. |year=2009 |title=Practice Parameter: Evaluation of the child with microcephaly (an evidence-based review) |journal=[[Neurology (journal)|Neurology]] |volume=73 |issue=11 |pages=887–897 |doi=10.1212/WNL.0b013e3181b783f7 |pmid=19752457 |pmc=2744281 }}</ref>

===Congenital===
{{More citations needed section|date=February 2016}}
* Isolated
*# Familial ([[autosomal recessive]]) microcephaly<ref name="Health Encyclopedia">{{Cite encyclopedia|url=https://www.urmc.rochester.edu/encyclopedia/content.aspx?ContentTypeID=90&ContentID=P02610|title=Microcephaly in Children |encyclopedia=Health Encyclopedia |publisher=University of Rochester Medical Center|access-date=2019-07-30}}</ref>
*# [[Autosomal dominant]] microcephaly<ref>{{Cite web|url=https://rarediseases.info.nih.gov/diseases/3605/microcephaly-autosomal-dominant|title=Microcephaly autosomal dominant|publisher=Genetic and Rare Diseases Information Center|access-date=2019-07-30|archive-date=2020-09-21|archive-url=https://web.archive.org/web/20200921191508/https://rarediseases.info.nih.gov/diseases/3605/microcephaly-autosomal-dominant|url-status=dead}}</ref><ref>{{OMIM|617520|Microcephaly 18, Primary, Autosomal Dominant; MCPH18}}</ref>
*# [[X-linked]] microcephaly<ref name="Health Encyclopedia" />
*# Chromosomal (balanced rearrangements and ring chromosome)
* Syndromes
** Chromosomal
**# [[Poland syndrome]]<ref>{{Cite web|url=https://rarediseases.info.nih.gov/diseases/7412/poland-syndrome|title=Poland syndrome |publisher=Genetic and Rare Diseases Information Center |access-date=2019-07-30}}</ref>
**# [[Down syndrome]]<ref>{{Cite web|url=https://www.who.int/news-room/fact-sheets/detail/microcephaly|title=Microcephaly|publisher=World Health Organization|access-date=2019-07-30}}</ref>
**# [[Edward syndrome]]<ref>{{Cite web|title=Trisomy 18: MedlinePlus Medical Encyclopedia|url=https://medlineplus.gov/ency/article/001661.htm|access-date=2020-10-29|website=medlineplus.gov|language=en}}</ref>
**# [[Patau syndrome]]<ref>{{Cite web|title=Trisomy 13 {{!}} Genetic and Rare Diseases Information Center (GARD) – an NCATS Program|url=https://rarediseases.info.nih.gov/diseases/7341/trisomy-13|access-date=2020-10-29|website=rarediseases.info.nih.gov}}</ref>
**# Unbalanced rearrangements
** Contiguous gene deletion
**# 4p deletion ([[Wolf–Hirschhorn syndrome]])
**# 5p deletion ([[Cri-du-chat]])
**# 7q11.23 deletion ([[Williams syndrome]])
**# 22q11 deletion ([[DiGeorge syndrome]])
* Single gene defects
*# [[Smith–Lemli–Opitz syndrome]]
*# [[Seckel syndrome]]
*# [[Cornelia de Lange syndrome]]
*# [[Dihydropteridine reductase deficiency]] - in up to 25% of patients<ref name="pmid32456656">{{cite journal | vauthors = Opladen T, López-Laso E, Cortès-Saladelafont E, Pearson TS, Sivri HS, Yildiz Y, Assmann B, Kurian MA, Leuzzi V, Heales S, Pope S, Porta F, García-Cazorla A, Honzík T, Pons R, Regal L, Goez H, Artuch R, Hoffmann GF, Horvath G, Thöny B, Scholl-Bürgi S, Burlina A, Verbeek MM, Mastrangelo M, Friedman J, Wassenberg T, Jeltsch K, Kulhánek J, Kuseyri Hübschmann O | title = Consensus guideline for the diagnosis and treatment of tetrahydrobiopterin (BH4) deficiencies | journal = Orphanet Journal of Rare Diseases | volume = 15 | issue = 1 | pages = 126 | date = May 2020 | pmid = 32456656 | pmc = 7251883 | doi = 10.1186/s13023-020-01379-8 | url =  | doi-access = free }}</ref>
*# [[5,10-methenyltetrahydrofolate synthetase deficiency]]
*# [[Holoprosencephaly]]
*# [[Primary microcephaly]]<ref>{{cite journal|last1=Szczepanski|first1=Sandra|last2=Hussain|first2=MuhammadSajid|last3=Sur|first3=Ilknur|last4=Altmüller|first4=Janine|last5=Thiele|first5=Holger|last6=Abdullah|first6=Uzma|last7=Waseem|first7=SyedaSeema|last8=Moawia|first8=Abubakar|last9=Nürnberg|first9=Gudrun|last10=Noegel|first10=Angelika Anna|last11=Baig|first11=Shahid Mahmood|last12=Nürnberg|first12=Peter|title=A novel homozygous splicing mutation of CASC5 causes primary microcephaly in a large Pakistani family|journal=Human Genetics|date=30 November 2015|volume=135|issue=2|pages=157–170|doi=10.1007/s00439-015-1619-5|pmid=26621532|s2cid=2295608}}</ref>
*# [[Wiedemann-Steiner syndrome]]
* Acquired
** Disruptive injuries
**# [[Ischemic stroke]]<ref name="UpToDate">{{Cite web|url=https://www.uptodate.com/contents/microcephaly-in-infants-and-children-etiology-and-evaluation|title=Microcephaly in infants and children: Etiology and evaluation|work=[[UpToDate]]|access-date=2019-08-02}}</ref>
**# [[Hemorrhagic stroke]]<ref name="UpToDate" />
**# Death of a monozygotic twin
** [[Vertically transmitted infection]]s
**# [[Congenital cytomegalovirus infection]]<ref name="Mayo Clinic">{{Cite web|url=https://www.mayoclinic.org/diseases-conditions/microcephaly/symptoms-causes/syc-20375051|title=Microcephaly - Symptoms and causes|website=[[Mayo Clinic]]|access-date=2019-07-30}}</ref>
**# [[Toxoplasmosis]]<ref name="Mayo Clinic" />
**# [[Congenital rubella syndrome]]<ref name="Mayo Clinic" />
**# [[Congenital varicella syndrome]]<ref name="Mayo Clinic" />
**# [[Zika virus]] (see [[Zika fever#Microcephaly]])<ref>{{cite journal|title=Interim Guidelines for Pregnant Women During a Zika Virus Outbreak — United States, 2016|date=January 22, 2016|volume=65|issue=2|pages=30–33|journal=Morbidity and Mortality Weekly Report|author1=Emily E. Petersen|author2=Erin Staples|author3=Dana Meaney-Delman|author4=Marc Fischer|author5=Sascha R. Ellington|author6=William M. Callaghan|author7=Denise J. Jamieson|author7-link=Denise J. Jamieson|doi=10.15585/mmwr.mm6502e1|pmid=26796813|doi-access=free}}</ref>
** Drugs
**# [[Fetal hydantoin syndrome]]<ref name="Mayo Clinic" />
**# [[Fetal alcohol syndrome]]<ref name="Mayo Clinic" />
* Other
*# [[Radiation]] exposure to mother
*# Maternal [[malnutrition]]<ref name="Mayo Clinic" />
*# Maternal [[phenylketonuria]]<ref name="Mayo Clinic" />
*# Poorly controlled [[gestational diabetes]]
*# [[Hyperthermia]]
*# [[Maternal hypothyroidism]]
*# [[Placental insufficiency]]
*# [[Craniosynostosis]]<ref name="Mayo Clinic" />

===Postnatal onset===
{{More citations needed section|date=February 2016}}
* Genetic
** Inborn errors of metabolism
**# [[Congenital disorder of glycosylation]]<ref>{{Cite web|url=https://rarediseases.org/rare-diseases/congenital-disorders-of-glycosylation/|title=Congenital Disorders of Glycosylation|website=NORD (National Organization for Rare Disorders)|access-date=2019-08-01}}</ref>
**# [[Mitochondrial disorders]]<ref>{{Cite web|url=https://www.mito.org.au/mito-info/|title=Mito Info|website=Mito Foundation|access-date=2019-08-01}}</ref>
**# [[Peroxisomal disorder]]<ref>{{Cite web|url=https://www.orpha.net/consor/cgi-bin/OC_Exp.php?Lng=GB&Expert=912|title=Zellweger syndrome|website=Orphanet|access-date=2019-08-01}}</ref>
**# [[Glucose transporter]] defect<ref>{{Cite web|url=https://ghr.nlm.nih.gov/condition/glut1-deficiency-syndrome|title=GLUT1 deficiency syndrome|last=Reference|first=Genetics Home|website=Genetics Home Reference|access-date=2019-08-01}}</ref>
**# [[Menkes disease]]
**# [[Congenital disorders of amino acid metabolism]]<ref>{{Cite web|url=https://www.orpha.net/consor/cgi-bin/OC_Exp.php?Expert=2209&lng=EN|title=Maternal phenylketonuria|website=Orphanet|access-date=2019-08-01}}</ref>
**# [[Organic acidemia]]<ref>{{Cite journal|last1=Reddy|first1=Nihaal|last2=Calloni|first2=Sonia F.|last3=Vernon|first3=Hilary J.|last4=Boltshauser|first4=Eugen|last5=Huisman|first5=Thierry A. G. M.|last6=Soares|first6=Bruno P.|date=2018-05-01|title=Neuroimaging Findings of Organic Acidemias and Aminoacidopathies|journal=RadioGraphics|volume=38|issue=3|pages=912–931|doi=10.1148/rg.2018170042|pmid=29757724|issn=0271-5333|doi-access=free}}</ref>
* Syndromes
** Contiguous gene deletion
**# 17p13.3 deletion ([[Miller–Dieker syndrome]])<ref>{{OMIM|247200|Miller-Dieker Lissencephaly Syndrome; MDLS}}</ref>
** Single gene defects
**# [[Rett syndrome]] (primarily girls)
**# [[Nijmegen breakage syndrome]]
**# X-linked [[lissencephaly]] with abnormal genitalia
**# [[Aicardi–Goutières syndrome]]
**# [[Ataxia telangiectasia]]
**# [[Cohen syndrome]]
**# [[Cockayne syndrome]]
* Acquired
** Disruptive injuries
**# [[Traumatic brain injury]]<ref>{{Citation|last1=Joyce|first1=Tina|title=Pediatric Abusive Head Trauma (Shaken Baby Syndrome)|date=2019|url=http://www.ncbi.nlm.nih.gov/books/NBK499836/|work=National Center for Biotechnology Information|publisher=AU.S. National Library of Medicine|pmid=29763011|access-date=2019-07-30|last2=Huecker|first2=Martin R.}}</ref>
**# [[Hypoxic-ischemic encephalopathy]]<ref name="Mayo Clinic" />
**# [[Ischemic stroke]]<ref name="UpToDate" />
**# [[Hemorrhagic stroke]]<ref name="UpToDate" />
** Infections
**# Congenital [[HIV encephalopathy]]<ref>{{Cite journal|last1=Donald|first1=Kirsten A.|last2=Walker|first2=Kathleen G.|last3=Kilborn|first3=Tracy|last4=Carrara|first4=Henri|last5=Langerak|first5=Nelleke G|last6=Eley|first6=Brian|last7=Wilmshurst|first7=Jo M|date=2015|title=HIV Encephalopathy: pediatric case series description and insights from the clinic coalface|journal=AIDS Research and Therapy|volume=12|issue=1|page=2|doi=10.1186/s12981-014-0042-7|issn=1742-6405|pmc=4297380|pmid=25598835 |doi-access=free }}</ref>
**# [[Meningitis]]<ref>{{Cite journal|last1=Tibussek|first1=Daniel|last2=Sinclair|first2=Adriane|last3=Yau|first3=Ivanna|last4=Teatero|first4=Sarah|last5=Fittipaldi|first5=Nahuel|last6=Richardson|first6=Susan E.|last7=Mayatepek|first7=Ertan|last8=Jahn|first8=Peter|last9=Askalan|first9=Rand|date=2015|title=Late-Onset Group B Streptococcal Meningitis Has Cerebrovascular Complications|journal=The Journal of Pediatrics|volume=166|issue=5|pages=1187–92.e1|doi=10.1016/j.jpeds.2015.02.014|pmid=25919727}}</ref>
**# [[Encephalitis]]<ref>{{Cite journal|last1=Ramos|first1=Regina|last2=Viana|first2=Rafaela|last3=Brainer-Lima|first3=Alessandra|last4=Florêncio|first4=Telma|last5=Carvalho|first5=Maria Durce|last6=van Der Linden|first6=Vanessa|last7=Amorim|first7=Antonio|last8=Rocha|first8=Maria Ângela|last9=Medeiros|first9=Fabíola|date=2017|title=Perinatal Chikungunya Virus-Associated Encephalitis Leading to Postnatal-Onset Microcephaly and Optic Atrophy|journal=The Pediatric Infectious Disease Journal|volume=37|issue=1|pages=94–95|doi=10.1097/INF.0000000000001690|pmid=28737626|s2cid=31790738|issn=0891-3668}}</ref>
** Toxins
*** [[Chronic kidney failure]]<ref>{{Cite web|url=https://rarediseases.org/rare-diseases/galloway-mowat-syndrome/|title=Galloway-Mowat Syndrome|website=NORD (National Organization for Rare Disorders)|access-date=2019-08-02|archive-date=2021-03-11|archive-url=https://web.archive.org/web/20210311133130/https://rarediseases.org/rare-diseases/galloway-mowat-syndrome/|url-status=dead}}</ref>
** Deprivation
**# [[Hypothyroidism]]<ref>{{Cite journal|last1=Kurian|first1=Manju A|last2=Jungbluth|first2=Heinz|date=July 2014|title=Genetic disorders of thyroid metabolism and brain development|journal=Developmental Medicine and Child Neurology|volume=56|issue=7|pages=627–634|doi=10.1111/dmcn.12445|issn=0012-1622|pmc=4231219|pmid=24665922}}</ref>
**# [[Anemia]]<ref>{{Cite web|url=https://ghr.nlm.nih.gov/condition/fanconi-anemia|title=Fanconi anemia|last=Reference|first=Genetics Home|website=Genetics Home Reference|access-date=2019-08-02}}</ref>
**# [[Congenital heart disease]]<ref>{{Cite journal|last1=Damlich|first1=Jennifer|last2=Qato|first2=Roa|last3=Cruz|first3=Meredith|last4=Colon|first4=Maria|last5=Wilkins|first5=Isabelle|date=2009-07-01|title=Discussion: 'Microcephaly associated with congenital heart defect' by Barbu et al|url=https://www.ajog.org/article/S0002-9378(09)00556-0/abstract|journal=American Journal of Obstetrics & Gynecology|language=en|volume=201|issue=1|pages=e7–e12|doi=10.1016/j.ajog.2009.05.042|pmid=19576365|issn=0002-9378|doi-access=free}}</ref>
**# [[Malnutrition]]<ref>{{Cite web|url=https://www.cdc.gov/ncbddd/birthdefects/microcephaly.html|title=Facts about Microcephaly |date=2016-12-07|publisher=Centers for Disease Control and Prevention|access-date=2019-08-02}}</ref>

Genetic mutations cause most cases of microcephaly.<ref name="NIH2015" /> Relationships have been found between [[autism]], duplications of genes and [[macrocephaly]] on one side. On the other side, a relationship has been found between [[schizophrenia]], deletions of genes and microcephaly.<ref>{{cite journal |author1-link=Bernard Crespi|last1=Crespi |first1=B. |last2=Stead |first2=P. |last3=Elliot |first3=M. |title=Evolution in health and medicine Sackler colloquium: Comparative genomics of autism and schizophrenia |journal=  Proceedings of the National Academy of Sciences of the United States of America|volume=107 |issue=Suppl 1 |pages=1736–41 |date=January 2010 |pmid=19955444 |pmc=2868282 |doi=10.1073/pnas.0906080106 |bibcode=2010PNAS..107.1736C |doi-access=free }}</ref><ref>{{cite journal |title=Rare chromosomal deletions and duplications increase risk of schizophrenia |journal=Nature |volume=455 |issue=7210 |pages=237–241 |date=September 2008 |pmid=18668038 |doi=10.1038/nature07239 |bibcode = 2008Natur.455..237S |last1=Stone |first1=Jennifer L. |last2=O'Donovan |first2=Michael C. |last3=Gurling |first3=Hugh |last4=Kirov |first4=George K. |last5=Blackwood |first5=Douglas H. R. |last6=Corvin |first6=Aiden |last7=Craddock |first7=Nick J. |last8=Gill |first8=Michael |last9=Hultman |first9=Christina M. |last10=Lichtenstein |first10=Paul |last11=McQuillin |first11=Andrew |last12=Pato |first12=Carlos N. |last13=Ruderfer |first13=Douglas M. |last14=Owen |first14=Michael J. |last15=St Clair |first15=David |last16=Sullivan |first16=Patrick F. |last17=Sklar |first17=Pamela |last18=Purcell (Leader) |first18=Shaun M. |last19=Stone |first19=Jennifer L. |last20=Ruderfer |first20=Douglas M. |last21=Korn |first21=Joshua |last22=Kirov |first22=George K. |last23=MacGregor |first23=Stuart |last24=McQuillin |first24=Andrew |last25=Morris |first25=Derek W. |last26=O'Dushlaine |first26=Colm T. |last27=Daly |first27=Mark J. |last28=Visscher |first28=Peter M. |last29=Holmans |first29=Peter A. |last30=o'Donovan |first30=Michael C. |display-authors=6 |pmc=3912847}}</ref><ref>{{cite journal |vauthors=Dumas L, Sikela JM |title=DUF1220 domains, cognitive disease, and human brain evolution |journal=Cold Spring Harb. Symp. Quant. Biol. |volume=74 |pages=375–382 |year=2009 |pmid=19850849 |pmc=2902282 |doi=10.1101/sqb.2009.74.025 }}</ref> Several genes have been designated "MCPH" genes, after [[microcephalin]] (''MCPH1''), based on their role in brain size and primary microcephaly syndromes when mutated. In addition to microcephalin, these include ''[[WDR62]]'' (''MCPH2''), ''[[CDK5RAP2]]'' (''MCPH3''), ''[[KNL1]]'' (''MCPH4''), [[ASPM (gene)|''ASPM'']] (''MCPH5''), ''[[CENPJ]]'' (''MCPH6''), ''[[STIL]]'' (''MCPH7''), ''[[CEP135]]'' (''MCPH8''), ''[[CEP152]]'' (''MCPH9''), ''[[ZNF335]]'' (''MCPH10''), ''[[PHC1]]'' (''MCPH11'') and ''[[CDK6]]'' (''MCPH12'').<ref name="BMC" /> Moreover, an association has been established between common genetic variants within known microcephaly genes (such as ''MCPH1'' and ''CDK5RAP2'') and normal variation in brain structure as measured with [[magnetic resonance imaging]] (MRI){{nsmdns}}i.e., primarily brain [[Cerebral cortex|cortical]] surface area and total brain volume.<ref name="Rimol_2010">{{cite journal |bibcode=2010PNAS..107..384R |jstor=40536283 |title=Sex-dependent association of common variants of microcephaly genes with brain structure |last1=Rimol |first1=Lars M. |last2=Agartz |first2=Ingrid |last3=Djurovic |first3=Srdjan |last4=Brown |first4=Andrew A. |last5=Roddey |first5=J. Cooper |last6=Kahler |first6=Anna K. |last7=Mattingsdal |first7=Morten |last8=Athanasiu |first8=Lavinia |last9=Joyner |first9=Alexander H. |last10=Schork |first10=N. J. |last11=Halgren |first11=E. |last12=Sundet |first12=K. |last13=Melle |first13=I. |last14=Dale |first14=A. M. |last15=Andreassen |first15=O. A. |last16=Weiner |first16=M. |last17=Thal |first17=L. |last18=Petersen |first18=R. |last19=Jack |first19=C. R. |last20=Jagust |first20=W. |last21=Trojanowki |first21=J. |last22=Toga |first22=A. W. |last23=Beckett |first23=L. |last24=Green |first24=R. C. |last25=Gamst |first25=A. |last26=Potter |first26=W. Z. |last27=Montine |first27=T. |last28=Anders |first28=D. |last29=Bernstein |first29=M. |last30=Felmlee |first30=J. |volume=107 |year=2010 |pages=384–8 |journal=Proceedings of the National Academy of Sciences |doi=10.1073/pnas.0908454107 |pmid=20080800 |issue=1 |pmc=2806758|display-authors=6 |doi-access=free }}</ref>

===Arbovirus===
[[Arthropod bites and stings|Bites and stings from Arthropods]] can often be a cause of [[disease vector|vector-borne diseases]]. These include [[mosquitoes]], [[fleas]], [[sand flies]], [[lice]], [[ticks]], and [[mites]] that are [[hematophagous]] vectors. The [[Centers for Disease Control]] (CDC) stated that "mosquitoes kill more people than any other creature and considers that mosquitoes are "the most dangerous animals on earth".<ref>{{cite web |title=Mosquitos kill more people than any other creature, the CDC warns |website=NPR.org  |url=https://www.npr.org/2024/07/08/nx-s1-5026612/mosquitos-kill-more-people-than-any-other-creature-the-cdc-warns |publisher=NPR Morning Edition|date= 8 July 2024|access-date=6 October 2024|archive-url= |archive-date= }}</ref>

The spread of [[Aedes]] mosquito-borne [[Zika virus]] has been implicated in increasing levels of congenital microcephaly by the [[International Society for Infectious Diseases]] and the US [[Centers for Disease Control and Prevention]].<ref>{{cite web |title=Zika virus - Brazil: confirmed Archive Number: 20150519.3370768 |website=Pro-MED-mail |url=http://www.promedmail.org/direct.php?id=3370768 |publisher=International Society for Infectious Diseases |url-status=live |archive-url=https://web.archive.org/web/20160130023132/http://www.promedmail.org/direct.php?id=3370768 |archive-date=2016-01-30 }}</ref> Zika can spread from a pregnant woman to her fetus. This can result in other severe brain malformations and birth defects.<ref name="NEJM201604">{{cite journal|last1=Rasmussen|first1=Sonja A.|last2=Jamieson|first2=Denise J.|last3=Honein|first3=Margaret A.|last4=Petersen|first4=Lyle R.|title=Zika Virus and Birth Defects — Reviewing the Evidence for Causality|journal=New England Journal of Medicine|date=13 April 2016|doi=10.1056/NEJMsr1604338|volume=374|issue=20|pages=1981–7|pmid=27074377|s2cid=20675635|doi-access=free}}</ref><ref>{{cite web|title=CDC Concludes Zika Causes Microcephaly and Other Birth Defects|url=https://www.cdc.gov/media/releases/2016/s0413-zika-microcephaly.html|website=CDC|access-date=1 June 2016|date=13 April 2016|url-status=live|archive-url=https://web.archive.org/web/20160531221123/http://www.cdc.gov/media/releases/2016/s0413-zika-microcephaly.html|archive-date=31 May 2016}}</ref><ref>{{cite web| url=https://www.cdc.gov/media/releases/2016/s0315-zika-virus-travel.html| title=CDC issues interim travel guidance related to Zika virus for 14 Countries and Territories in Central and South America and the Caribbean| publisher=Centers for Disease Control and Prevention| date=2016-01-15| access-date=2016-01-17| url-status=live| archive-url=https://web.archive.org/web/20160118024439/http://www.cdc.gov/media/releases/2016/s0315-zika-virus-travel.html| archive-date=2016-01-18}}</ref><ref>{{cite web|url=http://arstechnica.co.uk/science/2016/01/cdc-issues-travel-advisory-for-14-countries-with-alarming-viral-outbreaks/|title=CDC issues travel advisory for 14 countries with alarming viral outbreaks|author=Beth Mole|publisher=[[Condé Nast]]|work=[[Ars Technica]]|date=2016-01-17|access-date=2016-01-17|url-status=live|archive-url=http://archive.wikiwix.com/cache/20160118092344/http://arstechnica.co.uk/science/2016/01/cdc-issues-travel-advisory-for-14-countries-with-alarming-viral-outbreaks/|archive-date=2016-01-18}}</ref> A study published in The New England Journal of Medicine has documented a case in which they found evidence of the Zika virus in the brain of a fetus that displayed the morphology of microcephaly.<ref>{{Cite journal|last1=Mlakar|first1=Jernej|last2=Korva|first2=Misa|last3=Tul|first3=Nataša|last4=Popović|first4=Mara|last5=Poljšak-Prijatelj|first5=Mateja|last6=Mraz|first6=Jerica|last7=Kolenc|first7=Marko|last8=Resman Rus|first8=Katarina|last9=Vesnaver Vipotnik|first9=Tina|date=2016-03-10|title=Zika Virus Associated with Microcephaly|journal=New England Journal of Medicine|volume=374|issue=10|pages=951–8|doi=10.1056/NEJMoa1600651|issn=0028-4793|pmid=26862926|s2cid=205099844|doi-access=free}}</ref>

===Microlissencephaly===
{{Main|Microlissencephaly}}
[[Microlissencephaly]] is microcephaly combined with [[lissencephaly]] (smooth brain surface due to absent [[Sulcus (neuroanatomy)|sulci]] and [[gyri]]). Most cases of microlissencephaly are described in consanguineous families, suggesting an [[autosomal recessive inheritance]].<ref name="Cavallin">{{Cite journal|last1=Cavallin|first1=Mara|last2=Rujano|first2=Maria A.|last3=Bednarek|first3=Nathalie|last4=Medina-Cano|first4=Daniel|last5=Bernabe Gelot|first5=Antoinette|last6=Drunat|first6=Severine|last7=Maillard|first7=Camille|last8=Garfa-Traore|first8=Meriem|last9=Bole|first9=Christine|date=2017-10-01|title=WDR81 mutations cause extreme microcephaly and impair mitotic progression in human fibroblasts and Drosophila neural stem cells|journal=Brain|volume=140|issue=10|pages=2597–2609|doi=10.1093/brain/awx218|issn=1460-2156|pmid=28969387|doi-access=free}}</ref><ref>{{Cite book|url={{GBUrl|AmZgmGG4Dz0C|pg=PA309}}|title=Caffey's Pediatric Diagnostic Imaging E-Book|last=Coley|first=Brian D.|date=2013 |publisher=Elsevier Health Sciences|isbn=978-1-4557-5360-4 |edition=12th |oclc=847214216}}</ref><ref>{{Cite book|url={{GBUrl|AnVYBAAAQBAJ|pg=PA838}}|title=Fanaroff and Martin's Neonatal-Perinatal Medicine E-Book: Diseases of the Fetus and Infant|last1=Martin|first1=Richard J.|last2=Fanaroff|first2=Avroy A.|last3=Walsh|first3=Michele C.|date=2014 |publisher=Elsevier Health Sciences|isbn=978-0-323-29537-6 |oclc=909892605}}</ref>

===Historical causes of microcephaly===

After the dropping of [[atomic bombs]] "Little Boy" on [[Hiroshima]] and "Fat Man" on [[Nagasaki]], several women close to [[ground zero]] who had been pregnant at the time gave birth to children with microcephaly.<ref>{{cite web|url=http://www.pcf.city.hiroshima.jp/kids/KPSH_E/hiroshima_e/sadako_e/subcontents_e/13kousyougai_1_e.html#|title=Aftereffects|archive-url=https://web.archive.org/web/20090525013355/http://www.pcf.city.hiroshima.jp/kids/KPSH_E/hiroshima_e/sadako_e/subcontents_e/13kousyougai_1_e.html|archive-date=2009-05-25|url-status=live}}</ref> Microcephaly was present in 7 children from a group of 11 pregnant women at 11–17 weeks of [[gestation]] who survived the blast at less than {{convert|1.2|km|mi|abbr=on}} from ground zero.<ref name=Kalter10>{{cite book |chapter=Pioneering Studies §Atomic Radiation §Microcephaly and Mental Retardation |chapter-url={{GBUrl|DykKlVU0V-oC|pg=PA21}}|title=Teratology in the Twentieth Century Plus Ten|last1=Kalter|first1=Harold|date=2010 |publisher=Springer |isbn=978-90-481-8820-8 |page=21 |doi=10.1007/978-90-481-8820-8_2}}</ref> Due to their proximity to the bomb, the pregnant women's ''[[Uterus|in utero]]'' children received a [[Relative biological effectiveness|biologically significant radiation dose]] that was relatively high due to the massive [[neutron]] output of the lower explosive-yielding [[Little Boy]].<ref name=Kalter10/> Researchers studied 286 additional children who were in utero during the atomic bombings, and after a year they found these children had a higher incidence of microcephaly and mental retardation.<ref>{{Cite journal|last1=Burrow|first1=Gerard N.|last2=Hamilton|first2=Howard B.|last3=Hrubec|first3=Zdenek|date=June 1964|title=Study of Adolescents Exposed in Utero to the Atomic Bomb, Nagasaki, Japan|journal=[[Yale Journal of Biology and Medicine]]|volume=36|issue=6|pages=430–444 |pmc=2604646|pmid=14173443}}</ref><ref name=Kalter10/>

=== Other relations ===
Intracranial volume also affects this pathology, as it is related with the size of the brain.<ref>{{Cite journal|last1=Adams|first1=Hieab H. H.|last2=Hibar|first2=Derrek P.|last3=Chouraki|first3=Vincent|last4=Stein|first4=Jason L.|last5=Nyquist|first5=Paul A.|last6=Rentería|first6=Miguel E.|last7=Trompet|first7=Stella|last8=Arias-Vasquez|first8=Alejandro|last9=Seshadri|first9=Sudha|year=2016|title=Novel genetic loci underlying human intracranial volume identified through genome-wide association|journal=Nature Neuroscience|volume=19|issue=12|pages=1569–82|doi=10.1038/nn.4398|pmid=27694991|pmc=5227112}}</ref>